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Über dieses Buch


This book (vol. 2) presents the proceedings of the IUPESM World Congress on Biomedical Engineering and Medical Physics, a triennially organized joint meeting of medical physicists, biomedical engineers and adjoining health care professionals. Besides the purely scientific and technological topics, the 2018 Congress will also focus on other aspects of professional involvement in health care, such as education and training, accreditation and certification, health technology assessment and patient safety. The IUPESM meeting is an important forum for medical physicists and biomedical engineers in medicine and healthcare learn and share knowledge, and discuss the latest research outcomes and technological advancements as well as new ideas in both medical physics and biomedical engineering field.

Inhaltsverzeichnis

Frontmatter

Patient Safety

Frontmatter

Off-label Use of Medical Devices in Cardiovascular Medicine—When the Final Decision About the Safety and Effectiveness Is Needed

The use of a medical device in cardiovascular medicine according to the instructions provides maximum quality and safety, which has been clinically tested and then clinically evaluated. When you use a medical device and do not follow the instructions for use, you use a medical device off-label. Off-label use of a medical device can be seen not as an extension of the clinical use of a medical device, but also as a way of expanding scientific knowledge. Some off-label uses of a medical device provide positive health effects, and some do not. Two examples of off-label use in cardiovascular medicine are presented. While the off-label use of drug-eluting stents is commonly accepted, the off-label use of continuous left ventricular assist devices as continuous flow total artificial hearts provide very poor clinical results. Medical doctors and their patients should know which off-label use method works and which does not.

David Macku

One Pulsatile Heart Pump Size Does Not Fit All Patients

One of the main principles of personalized medicine is to adapt health care to the specific needs of our patients. Based on this principle, medical devices should be tailored to the specific characteristics of the patients and doctors should choose medical devices for patients according to their size. Both pulsatile and continuous flow ventricular assist device help patients with heart failure. Every left ventricular assist device usually contains a pump that a cardiac surgeon connects to the apex of the heart. Pulsatile ventricular assist device systems using volume displacement pulsatile pumps are designed and mainly used for children patients. The first generation ventricular assist devices systems for adult patients relied on volume displacement pumps with one constant stroke volume for all sizes of patients. The concept of one size of the medical device for all patients goes against the principle of personalized medicine. A cardiovascular model in Modelica has confirmed that a pump with one constant pump stroke volume of 65 ml can generate uncontrolled flow and pressure curves oscillating over the normotensive zone for small patients and under the normotensive zone for large patients. The one pulsatile pump size for all patients may cause harm due to non-physiological flow and pressure condition in circulations.

David Macku, Iva Novotna

Effect of Weight Input in Magnetic Resonance Imaging System on Radio-Frequency-Induced Heating of Metallic Implants

Radio-frequency-(RF)-induced heating in clinical magnetic resonance imaging (MRI) may pose risks to patients with metallic implants. The specific absorption rate (SAR), a representative index for the estimation of a temperature increase, may be influenced by the weight input in the MR system. We investigate the RF-induced heating of implants as a function of the weight input in the MRI system. The employed measurement method for the implant heating conformed to the American Society for Testing and Materials (ASTM) F2182-11a criteria. Two different implants (titanium-alloy humeral nail and stainless-steel shaft) were analyzed. All experiments were performed using a clinical 1.5-T MR system. MRI was performed using a transmit/receive radio-frequency body coil at a whole-body average SAR of 2.0 W/kg for 15 min. The weight input in the system was in the range of 10–200 kg. Temperature measurements of the implant tip were performed using a fiber optic thermometer system. For a weight of 60 kg, the highest temperature changes for the humeral nail and stainless-steel shaft were 3.9 °C and 5.9 °C, respectively, while for a weight of 200 kg, the highest temperature changes were 9.9 °C and 12.4 °C, respectively. The highest temperature change increased with the weight in the range of 10–140 kg. These findings suggest that even at a permissible SAR level, there are potential risks of RF heating on patients with implants, owing to the large input weight in the MRI system.

Atsushi Ono, Shinichi Arao, Satoru Takata, Tatsuhiro Gotanda, Rumi Gotanda, Akihiko Tabuchi

An Ergonomic Evaluation of Physical and Mental Loads in Standing-up Motion from Forward-Sloping Toilet Seats

We aim to develop a new in-home assistance system to aid in the standing-up motion from toilet seats in assisted bathrooms. The underlying design concept for accessible toilet facilities is to use a novel compact actuation device—a metal hydride actuator with several unique properties such as softness, noiselessness, and being lightweight—for tilting a toilet seat when required, thus helping elderly or frail people to stand-up after excretion. This ergonomic study evaluates the easiness of the standing-up motion using both objective and subjective data from healthy participants, as a prior step before developing the envisaged toilet seat tilting system. In the experiment, the participants were monitored to obtain simultaneous objective data concerning muscle activity, 3D body motion, center of pressure, and seat pressure distribution. Additionally, all participants were requested to provide subjective data (comfort scores) while standing up from a toilet seat under four different conditions—four different forward-tilting angles (0°, 5°, 10°, and 15°). All participants repeated the motion 25 times for each tilting angle, and provided feedback regarding their standing-up experience and feelings under each condition. According to the collected subjective data, a toilet seat tilt angle of approximately 10° increased the easiness and comfort of the standing-up motion. However, according to the measured objective data, the standing-up motion has individual variations in the electromyogram magnitude, center of pressure excursion, and seat pressure pattern, implying that to analyze the standing-up motion both the measured objective data and the perceived subjective data must be considered.

Shuichi Ino, Manabu Chikai, Emi Ozawa, Hiroshi Endo

Optimal Variable Refocus Flip Angle Control Method and Echo Train Length for Suppressing Exposure to Radio Frequency

The popularization of 3-Tesla magnetic resonance imaging (MRI) has improved the quality of images and shortened typical examination times. However, a side effect of this is increased exposure to radio frequency (RF) radiation. The amount of RF exposure can be controlled using a technique called variable refocus flip angle (vRFA). Controlling vRFA is also an important for improving the signal to noise ratio (SNR) and for reducing blurring on MRI images. In this study, we examined the influence of controlling vRFA and echo train length (ETL) on SNR. To do this, we used a device that can arbitrarily control three angles—the fifth RFA, the RFA centered in k-space, and the final RFA. Using a phantom, T1 and T2 values were made equal to gray- and white-matter, respectively. The repetition time was 5000 ms and echo time 90 ms. By setting the fifth RFA to 40° and using an ETL of 11–15, the signal shifted smoothly to a pseudo steady-state (PSS), and a stable signal was obtained. Further, we were able to suppress blurring by gently changing the k-space-centered RFA. In the final echo, we were able to maintain PSS by increasing the final RFA up to 180°, resulting in a high SNR. Results of this study showed the changes reduced RF exposure. Using an ETL of 30, blurring was reduced, though RFA control was similar to that used with ETLs of 11–15; although slightly higher RF exposure was required to obtain a high SNR, the fifth RFA was required to be 60°–90°.

Akihiko Tabuchi, Shinichi Arao, Toshizo Katsuda, Atsushi Ono, Tatsuhiro Gotanda, Rumi Gotanda

Fault Identification in a Blood Pump Using Neural Networks

This paper compares two fault identification implementations based on a neural network and a model based approach. Our worked example is the detection of gas bubbles in the pump head of a centrifugal blood pump. We focus on algorithms applicable on minimal sensor data with a reasonable implementation effort. The approaches were restricted to the desired blood flow and the measured rotational speed of the pump. We evaluated both implementations with data from an ECMO system.

Jan Kühn, Mateusz Buglowski, André Stollenwerk, Stefan Kowalewski, Marian Walter, Steffen Leonhardt, Jan Petran, Rüdger Kopp, Rolf Rossaint, Thorsten Janisch

Elaboration of New NDRLs as Part of Third National Patient Dose Survey in Diagnostic Radiology in Bulgaria

Purpose: The aim of this research is to elaborate an update of National Diagnostic Reference Levels (NDRLs) in Bulgaria, as required by National and International legislation. Methods and Materials: Special questionnaires and methodology instructions for submission of required data were distributed to all hospitals in the country. Patient dose records and corresponding technical data were delivered from medical institutions via following three methods: by e-mail, by specialized on-line system, or by paper. A national patient dose database build on MS Access was elaborated and employed for storing, processing and analysing of the collected data. Results: More than 10,500 patient dose records on more than 190 X-ray systems from over 90 health establishments have been collected and analysed. New national DRLs were elaborated and proposed for: Chest PA, Pelvis AP, Abdomen AP, Thoracic Spine AP, Thoracic Spine Lat, Lumbar Spine AP, Lumbar Spine Lat, Skull AP, Scull Lat, Barium meal, Barium enema, Coronary Angiography and Percutaneous Coronary Intervention—in terms of KAP; for Computed Tomography (CT) of Head, Abdomen and Lumbar Spine—in terms of CTDIw and DLP; for Mammography—in terms of ESAK and AGD. Conclusion: The new DRL values obtained are proposed as NDRLs for the country. Most are comparable with other European NDRLs with a few exceptions only. Those exceptions are most probably related to actual optimization in existing radiology practices.

Asen Dimov, Ivan Tsanev, Desislava Ivanova, Filip Simeonov

Development of Identification System for Surgical Instruments Using UHF Band RFID and Low-Intensity Antennae

Post-op vestigial remnant of surgical instruments in the body is a very serious problem. The current two-dimensional symbol system is being used to help manage this problem. However, the two-dimensional symbols have to be identified one at a time, since the symbols are a sort of printed matter. An HF band passive RFID system was also proposed. This system also had problems in identifying the signals of a large number of surgical instruments in bulk, since the scope of its identification area was relatively small. To improve the deficiencies of this system, a UHF band passive RFID system was developed. The authors have also proposed a new low-intensity antennae for the UHF band passive RFID system. This new system cannot radiate an electrical field strong enough to interfere with medical equipment and should not pose a problem to any electronic equipment in the operating room. From our experimental results using 50 surgical instruments, all the instruments were identified in less than one second with this new RFID system, even when the instruments were covered with water residue. These results are very promising and indicate that the proposed RFID system will be an improvement to the surgical instrument management systems currently being used. This new system will also undoubtedly reduce the workload of surgical nurses, while reducing human error in the operating room.

Ryosuke Hosaka

Establishing Traceability Chain of Infusion and Perfusor Pumps Using Legal Metrology Procedures in Bosnia and Herzegovina

Establishing the traceability chain of measurements for medical devices (MDs) commonly used in everyday patient treatment was the main objective of this paper. This should directly ensure that through periodical calibrations of etalons and independent inspection procedure of MDs according to international standards, safe and accurate diagnosis and treatment can be created. This study is designed to cover 850 perfusors and 700 infusion pumps used in public and private healthcare institutions, during a period of one year. Testing procedures were carried out according to international standards and legal metrology legislative procedures in Bosnia and Herzegovina. The results show that the average measurement uncertainty of infusion pump is 0.9 ml, while for perfusor pump is 0.7 ml. These obtained results combined with other relevant documents, references and competences create the traceability chain. Additionally, as consequence cost benefits analysis proved yearly savings of 50% if healthcare institutions follow legal metrology procedures compared with unnecessary manufactures attests. Research emphasizes importance of establishing traceability chain in protection of public health. Results offered also implications for adequacy of etalon calibration and preventive maintenance performed on MDs. Based on collected measurement data, web-based application with database of infusion and perfusor pumps used in healthcare institutions in Bosnia and Herzegovina was created.

Lejla Gurbeta, Zijad Džemic, Almir Badnjevic

Medical Devices Safety Enhancement and Performance Improvement Through a Periodic Calibration Program

Today’s have been seen more than 10,000 different types of medical devices in medical centers and hospitals. Physicians need better accurate medical measurements to better diagnosing diseases, monitoring patients and delivering treatments. The lack of correct and appropriate measurements will certainly have diverse effects in diagnostic and treatment procedures. In 1999, Institute of Medicine reported more than 44,000 medical error deaths annually in medical centers. Safety and performance testing of medical devices in the medical sector is a one of the key factor in improving public health. Acquiring results of some investigations demonstrate a need for new and severe regulations on periodic performance verifications especially in high-risk equipment. The metrological reliability of four high risk medical devices, Electrosurgical unit, Defibrillator, Syringe pump and Infant incubator in use some medical centers and hospitals (privates and publics) according to international and national standards were evaluated. Quantitative analysis of some parameters that impact the safety and performance represented the amount of the obtained results in some equipment are in critical range with higher values than standard limitations. Acquiring results represent a need for severe regulations on periodic performance verifications and quality control program especially in high-risk equipment. Also it is necessary to provide training courses for operating staff in the field of meterology in medicine. One of the main aim of these training courses is to present what’s the critical operation parameters and how the operators can get good accuracy results on each medical devices.

A. Tavakoli Golpaygani, M. M. Movahedi, H. Hafezi

Legal Metrology Procedures for Increasing Safety and Performance Characteristics with Cost Benefits Analysis: Case Study Dialysis Machines

The objective of this paper was to increase safety and performance characteristics with cost benefits of medical devices (MDs) by introducing legal metrology procedures. This should directly improve the quality of patient safety and re-liability of treatment. This study is designed to cover 1100 dialysis machines used in public and private healthcare institutions, during a period of three years. Testing procedures were carried out according to international standards and legal metrology legislative procedures in Bosnia and Herzegovina. The results show that the average rate of faulty devices during three years testing period is 36.33% and should either have its results be verified, or the device removed from use or scheduled for corrective maintenance. Additionally, cost benefits analysis shows yearly savings of 30% if healthcare institutions follow legal metrology procedures compared with unnecessary manufactures attests. Research emphasizes importance of independent safety and performance inspections and gives recommendations for the frequency of inspection based on measurements. Results offer implications for adequacy of preventive and corrective maintenance performed in healthcare institutions. Based on collected measurement data, web-based application with database of dialysis machines used in healthcare institutions in Bosnia and Herzegovina is created. Thus, legal metrology procedures enabled establishing traceability chain for this type of MDs.

Lejla Gurbeta, Dijana Vukovic, Zijad Džemic, Almir Badnjevic

In Vivo Dosimetry in Total Body Irradiation

Total Body Irradiation (TBI) is a radiotherapy technique that consists of irradiating homogeneously the whole patients body and it is characterized by extended source to surface distances and the use of large irradiation fields. The limitations of the available input data and inherent problems with the calculation procedures make it very difficult to accurately determine the dose distributions in TBI. For these reasons, it is highly recommended to use In Vivo Dosimetry (IVD), to guarantee the quality of TBI treatments as a direct measurement of the delivered dose. An IVD QA system was implemented based on semiconductor diodes and radiochromic films. For the commissioning of the system, both detector types were calibrated independently. This guarantees the traceability of the measurements. An assessment was made on the sources of uncertainties. A tolerance level of ±10% was established for the combined contribution of both computational and experimental uncertainties. An experiment to a phantom was carried out to simulate a clinical TBI procedure. In this way, the calibration of the dosimetry system was corroborated. Finally, the IVD system was applied in TBI of three real patients. The discrepancies obtained between the prescribed and measured doses were below the established tolerance level of ±10%.

Eilen Llanes Veiga, Rodolfo Alfonso Laguardia, Roberto Caballero Pinelo

Accreditation and Certification

Frontmatter

Documentation Template for the Usability Engineering Process for Medical Devices

Introduction: Medical device regulatory processes are currently based on technical (ISO IEC 62366:2015) and regulatory standards (IEC ISO 60601-1-6:2015), which provide an international standard to be applied in evaluating devices and their documentation. However, the lack of standardization in the usability engineering processes used by the manufacturers, and the absence of pre-established metrics for such processes are constant problems in the medical device universe, particularly hindering the evaluation processes. It was verified that the current norms are insufficient to guarantee good usability engineering processes, even with the existence of good usability practices in the literature. Objective: This paper presents an analysis of the requirements contained in current standards and proposes a documentation model for usability engineering of medical devices, from the presentation of some techniques that are used in the process of device development. Method: This work is based on literature reviews to identify the state of the art in usability engineering; analysis of current standards, to verify what the regulatory requirements are, and how to comply with them; comparative studies with existing documentation to identify strengths and weaknesses in documentation processes; and elaboration of documentation prototypes. Results: From these results, it was possible to prepare a template document with all the points required by the current norms. Appropriate techniques were also listed for the accomplishment of some stages of the process, creating greater rigidity in the definition of the parameters of the documentation.

Daniel Scherer, Francisco Ferreira Gouveia Filho

Health Technology Assessment

Frontmatter

Cost-Effectiveness of Minimally Invasive Total Hip Endoprosthesis Implantation as Compared with the Conventional Approach

Objectives: The total hip endoprosthesis implantation is one of the most common surgical procedures of the present day, and surgeons can choose different approaches. The aim of this study is to compare two surgical approaches—the conventional approach and the minimally invasive approach. Methods: Clinical outcomes have been obtained through a literature review of clinical trials. Value engineering methods and multiple-criteria decision methods—namely Saaty’s matrix, the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) and the Analytic Hierarchy Process (AHP)—were used for setting the scales of criteria and effects, respectively. The total direct costs per patient were carried out by a systematic cost analysis from the healthcare provider’s perspective. The cost-effectiveness analysis compared the conventional and the minimally invasive approaches. The calculations were completed by a sensitivity analysis. Results: A total of 180 patients were enrolled in the study. The total costs per patient were CZK 57 084 (~EUR 2 243) for the conventional approach, and CZK 54 321 (~EUR 2 134) for the minimally invasive approach. Applying the TOPSIS method, the cost-effectiveness ratio is CZK 125 157 (~EUR 4 917) for the conventional approach, and CZK 88 586 (~EUR 3 480) for the minimally invasive approach. These results were also confirmed using the AHP method, when the C/E ratio is CZK 112 859 (~EUR 4 434) for the conventional approach, and CZK 106 116 (~EUR 4 169) for the minimally invasive approach. Conclusions: The results based on the cost-effectiveness analysis show that the minimally invasive approach to the total hip endoprosthesis implantation is more cost-effective than the conventional approach.

Tereza Lísalová, Ondřej Gajdoš

The Robustness of TOPSIS Results Using Sensitivity Analysis Based on Weight Tuning

Multiple-criteria decision analysis (MCDA) is one of the support techniques for Health Technology Assessment (HTA). A typical method is the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS). The output of TOPSIS presents an order of alternatives. A significant risk may be posed by an inappropriate setup of the weights of the criteria such that a very small deviation from the proper value could substantially change the final result. Sensitivity analysis is a method for testing changes of the final order by a modification of the original input data or by small deviation of the original weights of the criteria. This original approach is very slow and computationally demanding in the case of a change of the value of any attribute. The newly proposed method is significantly faster, making it possible to change of the values of the weights by only a few computations within TOPSIS. In the first stage, TOPSIS is used to compute the values of the Positive and Negative Ideal Solutions (PIS and NIS), and sensitivity analysis is only performed for the changed weights in the next stage. In the proposed method, a weight is adjusted (and the other weights recalculated) in order to find a range where the order of the alternatives remains unchanged for the modified weights. The weight adjustment can have the form of a fixed change or of an iterative process approximating the stability range for the weight. The new method is fast and simple to implement, providing a robust output of TOPSIS and pointing out a possible wrong setup of the initial weight(s).

Millek Jiří

Application of HTA in Optometry

The main objective was to evaluate possible options for refractive error correction for three categories of clients (children from 6 years with light myopia, teenagers from 15 with astigmatism, adults with starting presbyopia) considering the available correction methods (glasses, contact lenses, refractive surgery). The evaluation was performed through data on the amount and frequency of orders in an optical shop and eye clinic. The data were gradually processed and the calculation of the cost of correction was performed from the perspective of a client. FMEA was done for individual methods of correction, and multiple-criteria evaluation applying the TOPSIS method was figured out. The TOPSIS method alone showed the glasses correction to be the best. The CEA, i.e. after considering the economic view, prioritized the contact lens correction. The best possible combination of correction methods for the refractive errors is, due to possible health risks, the combination of correction with glasses and contact lenses.

Miroslav Selčan, Ivana Kubátová

A Preliminary Cost/Efficacy Analysis of MIRUS™ System for Sedation of Critical Patients

Introduction Side effects of traditional analgo-sedative agents call the attention to alternative strategies of sedation for critically ill patients; volatile anaesthetics (VAs) are considered potential substitutes in selected categories of patients. MIRUS™ (Pall Corporation and TIM Germany) is an innovative system for the administration of VAs to these patients admitted in intensive care unit (ICU). Methods The aim of this study was to analyse the clinical and economical characteristics of MIRUS™, following the Health Technology Assessment principles (HTA); in particular, the study was focused on defining a cost/efficacy ratio of the use of MIRUS™ in an ICU with 8 beds and 80 procedures/year. HTA allows predicting the system impact in the clinical pathway before material introduction. Results The assessment showed that MIRUS™ could be innovative, safe and efficient, especially when applied to critically ill patients with compromised organ function. For the purposes of assessment, three classes of ICU treatments have been defined: short- (6–24 h), medium- (24–96 h) and long-term (>96 h) sedation (SS, MS, LS). Based on the technical characteristics of system, MIRUS™ could be considered unfit for LS. Considering clinical characteristics, effects on patients, sedation times and costs, the HTA shows how the procedure costs are different for each class. Conclusions In conclusion, the use of MIRUS™ could be useful and effective for critically ill patients, in which standard sedation may be associated with drug hangover. This assessment seems economically advantageous for SS, where cost/efficacy ratios are positive performing 400 procedures/year, while for MS the cost of drugs impacts on the procedure cost. Therefore, looking at the potential clinical benefits on all potential treatable patients, the best addition strategy of the system in the hospital should be evaluated to optimize the cost/efficacy ratio.

E. Ciagli, F. Frosini, D. Cocchi, P. Tortoli, S. Romagnoli, C. Quarti, A. R. De Gaudio, A. Belardinelli

HTA in the Czech Republic: Still Behind

The paper analyses the current state of HTA implementation and organisational initiatives in the Czech Republic. Although there have been some substantial elements of HTA applied in the decision process of pharmaceutical reimbursement since 2008, HTA methods are rather disregarded in other technologies. Since there is practically no demand for HTA studies from payers and state representatives, HTA has been cultivated above all by interested individuals and small academic research groups around them. These groups have succeeded in keeping pace with the global development both in theoretical and practical issues (among others in HTA methods for medical devices), however, the practical production of country specific HTA studies is rather rare. The main problem is non-existence of a national commonly accepted methodology and a legal framework. At least two attempts to establish a regular HTA process initiated by the Ministry of Health were destined to fail due to frequent personal changes in the Ministry. We discuss topical issues to be solved on the way to a national HTA system, and present our vision of a possible solution.

Vladimír Rogalewicz, Ivana Kubátová, Gleb Donin, Tomáš Doležal, Klára Lamblová, Jana Bartáková, Peter Kneppo

Cost-Effectiveness Analysis of Intrabeam System Introduction to the Czech Healthcare System Environment

Backround: Intrabeam system is a technology used in oncology for intraoperative radiotherapy (IORT), a technique of partial delivery of radiation therapy to the tumour bed during surgery. The aim of this study is to evaluate cost effectiveness of the Intrabeam system compared to the standard treatment with external beam radiotherapy (EBRT) in early stage breast cancer treatment in order to reach a decision on a possible introduction of the technology to the Czech healthcare system. Methods: In order to determine the clinical effects, a worldwide literature review was conducted. The cost of the Intrabeam system was estimated based on available information about acquisitions of the system worldwide in the last 5 years. The cost of treatment was calculated from the perspective of a healthcare payer, and all the information gathered was summarized in a Markov model to finalize the cost-effectiveness calculation. A sensitivity analysis was performed. Results: The input of the model was based on the TARGIT-A pragmatic randomized controlled trial—the largest and most comprehensive study among 26 selected studies from the literature review. The estimated purchase cost of the system for the Czech Republic was determined in the range of CZK 16–20 million without VAT. Based on the findings, three versions (baseline, optimistic, pessimistic) of the calculation for IORT interventions using Intrabeam were determined. In the baseline scenario, the cost of the Intrabeam system intervention was CZK 38 559, the ICER value was CZK 53 483 saved per 1 QALY lost. The results of the sensitivity analysis are consistent with the results of the baseline scenario. The ICER value is not above the cost-effectiveness threshold (currently a little above CZK 1.2 million), which is required to consider the technology cost effective. Conclusion: According to the results of the cost-effectiveness analysis, we do not currently recommend the Intrabeam system to be introduced into the Czech healthcare system.

Vojtěch Kamenský, Gleb Donin, Veronika Burianová, Ondřej Gajdoš, Vladimír Rogalewicz, Ivana Kubátová, Silvie Jeřábková, Peter Kneppo

Economic Evaluation of Robotic Radiosurgery System for Prostate Cancer Treatments in the Czech Republic

The purpose of this study was to carry out the economic evaluation of robotic stereotactic body radiation therapy (rSBRT) in comparison with conventional intensity-modulated radiation therapy (IMRT) for the treatment of localized prostate cancer in the Czech Republic. Cost-utility analysis was used for the economic evaluation of both technologies based on their costs and the number of quality-adjusted life years gained (QALYs). Utilities of both technologies were identified in literature. An estimation of treatment costs was obtained from publicly available secondary sources for the Czech Republic. The cost-utility analysis was conducted from provider’s perspective for three scenarios (optimistic, realistic, and pessimistic). According to the results of cost-utility analysis, in every scenario concerned IMRT was both more effective and less costly than rSBRT. Namely, in realistic scenario, IMRT and rSBRT accrued 9.96 QALY/53,198 CZK and 9.93 QALY/79,956 CZK, respectively. rSBRT reached the same or lower values of the cost-utility ratio than IMRT in situation, when the acquisition price of rSBRT equipment was lower than CZK 58 million in the realistic scenario. Under the conditions of the Czech healthcare system, IMRT was more cost-effective than rSBRT for localized prostate cancer treatment in all the analyzed scenarios.

Denisa Horáková, Gleb Donin

Biosignals Processing

Frontmatter

Usability of Volume Pulse Wave Biosignal

The aim of this study is to show the usability of volume pulse wave measurement on superficial arteries, using a method as close as possible to manual palpation. The parameters evaluated can be generally assessed from the time domain, derivations, velocity, or frequency domain. In the time domain, a number of wave proportions can be measured. In this study, the parameters were derived from time and amplitude measurement of the pulse wave run. The mean coefficients of variation in (%) of parameters in one pulse waveform were: crest time 11.8; systolic amplitude 8.45; relative crest time 11.38; interwave distance 12.97; relative dicrotic amplitude 23.1; relative dicrotic time 7.15; augmentation index 13.23; PWV 6.76. The mean coefficients of variation in (%) of parameters in the long-term measurement were: crest time 9.17; systolic amplitude 10.79; relative crest time 6.91; interwave distance 3.77; relative dicrotic amplitude 11.37; relative dicrotic time 1.87; augmentation index 4.58; PWV 5.87. The variations measured are very large. As a result, it is not possible to accurately and quantitatively evaluate the pulse wave measured by palpation. The results show that the coefficients of variation for the parameters of the volume pulse wave biosignal can increase up to double-digit values.

D. Korpas, J. Haluzikova

Stable EEG Spatiospectral Sources Using Relative Power as Group-ICA Input

Within the last decade, various blind source separation algorithms (BSS) isolating distinct EEG oscillations were derived and implemented. Group Independent Component Analysis (group-ICA) is a promising tool for decomposing spatiospectral EEG maps across multiple subjects. However, researchers are faced with many preprocessing options prior to performing group-ICA, which potentially influences the results. To examine the influence of preprocessing steps, within this article we compare results derived from group-ICA using the absolute power of spatiospectral maps and the relative power of spatiospectral maps. Within a previous study, we used K-means clustering to demonstrate group-ICA of absolute power spatiospectral maps generates sources which are stable across different paradigms (i.e. resting-state, semantic decision, visual oddball) Within the current study, we compare these maps with those obtained using relative power of spatiospectral maps as input to group-ICA. We find that relative EEG power contains 10 stable spatiospectral patterns which were similar to those observed using absolute power as inputs. Interestingly, relative power revealed two γ-band (20–40 Hz) patterns which were present across 3 paradigms, but not present using absolute power. This finding suggests that relative power potentially emphasizes low energy signals which are obscured by the high energy low frequency which dominates absolute power measures.

René Labounek, David A. Bridwell, Radek Mareček, Martin Lamoš, Michal Mikl, Milan Brázdil, Jiří Jan, Petr Hluštík

Simulation of Required CPAP Usage to Normalize AHI in Obstructive Sleep Apnea Patients

Obstructive sleep apnea (OSA) is a highly prevalent disease with severe health consequences. The severity of OSA is estimated with apnea-hypopnea-index (AHI). OSA is often treated with continuous positive airway pressure (CPAP). The aim of the current work was to create a numerical simulator showing benefits of different levels of usage of CPAP treatment. 226 male OSA patients were evaluated. CPAP treatment was simulated in 5 min intervals starting from the beginning of the night and continuing until the end. The cutoff point where AHI reached normal level of <5 events/h were determined for mild, moderate and severe OSA categories. We found a trend of increasing AHI towards the end of the night. The median values of required simulated CPAP usage times to normalize the AHI values (AHI < 5 events/h) were 3.9 h, 5.3 h and 6.2 h in the mild, moderate and severe OSA severity categories, respectively. CPAP treatment adherence can be limited in OSA patients due to several reasons. The presented CPAP treatment simulation tool could aid the clinicians to give patient specific recommendation to the OSA patients for required CPAP treatment times and to motivate the patients to higher adherence levels of the treatment. This could possibly better prevent the harmful health consequences related to OSA.

Antti Kulkas, Sami Nikkonen, Juha Töyräs, Esa Mervaala, Timo Leppänen

SAHS Patients’ Classification Based on Oximetry and Respiratory Effort Signal: An Alternative Method

The “Gold Standard” for Sleep Apnea/Hypopnea Syndrome (SAHS) diagnosis is the study of Polysomnography (PSG) in a sleep laboratory. It consists of connect to patient’s body several sensors. The standards are the oronasal airflow (OAS) and pulse oximeter (SpO2) sensors while Respiratory Inductance Plethysmography sensor (RIP) is alternative. The airflow signal can be estimated from RIP signal (RIPFlow). Hypopneas are detected in %SpO2 desaturation events through baseline. However, there isn’t a consensus about this value’s definition. The signals sent by such sensors are analyzed by an expert to get the Apnea/Hypopnea Index (AHI) and to classify the patients into four groups: Normal, Mild, Moderate and Severe. In this study, an alternative method for scoring apnea/hypopnea events based on thorax and abdomen RIP sensor and for analyzing the %SpO2 values variations using Median Absolute Deviation (MAD) is proposed. For time domain comparison, the Pearson’s correlation coefficient was computed on the RIPFlow with the respiratory flow signal. Also, the automatic algorithms from standard and proposed method were implemented to obtain AHI. In order to test the proposed method’s performance, PSG recordings acquired in 23 adult patients are used. The Sensitivity (Sen), Specificity (Sp) and Accuracy (Acc) values were calculated considering patients classification for the standard method and well as the one proposed. Results indicate a high correlation (p-value < 0.05) in flow estimation and an improvement in patient classification using the model based on the RIPflow and the MAD-SpO2.

C. Dell’Aquila, L. Correa, R. Correa, G. Cañadas, E. Laciar

Electrical Right and Left Cardiac Atrioventricular and Left Atrial Delay in Cardiac Resynchronization Therapy Responder and Non-responder with Sinus Rhythm

Cardiac resynchronization therapy (CRT) with hemodynamic optimized biventricular pacing is an established therapy for heart failure patients with sinus rhythm, reduced left ventricular ejection fraction and wide QRS complex. The aim of the study was to evaluate electrical right and left cardiac atrioventricular delay and left atrial delay in CRT responder and non-responder with sinus rhythm. Methods: Heart failure patients with New York Heart Association class 3.0 ± 0.3, sinus rhythm and 27.7 ± 6.1% left ventricular ejection fraction were measured by surface ECG and transesophageal bipolar left atrial and left ventricular ECG before implantation of CRT devices. Electrical right cardiac atrioventricular delay was measured between onset of P wave and onset of QRS complex in the surface ECG, left cardiac atrioventricular delay between onset of left atrial signal and onset of left ventricular signal in the transesophageal ECG and left atrial delay between onset and offset of left atrial signal in the transesophageal ECG. Results: Electrical atrioventricular and left atrial delay were 196.9 ± 38.7 ms right and 194.5 ± 44.9 ms left cardiac atrioventricular delay, and 47.7 ± 13.9 ms left atrial delay. There were positive correlation between right and left cardiac atrioventricular delay (r = 0.803 P < 0.001) and negative correlation between left atrial delay and left ventricular ejection fraction (r = −0.694 P = 0.026) with 67% CRT responder. Conclusions: Transesophageal electrical left cardiac atrioventricular delay and left atrial delay may be useful preoperative atrial desynchronization parameters to improve CRT optimization.

Matthias Heinke, Gudrun Dannberg, Tobias Heinke, Helmut Kühnert

Spectral Analysis of Signal Averaging Electrocardiography in Atrial and Ventricular Tachycardia Arrhythmias

Targeting complex fractionated atrial electrocardiograms detected by automated algorithms during ablation of persistent atrial fibrillation has produced conflicting outcomes in previous electrophysiological studies and catheter ablation of atrial fibrillation and ventricular tachycardia. The aim of the investigation was to evaluate atrial and ventricular high frequency fractionated electrical signals with signal averaging technique. Methods: Signal averaging electrocardigraphy allows high resolution ECG technique to eliminate interference noise signals in the recorded ECG. The algorithm use automatic ECG trigger function for signal averaged transthoracic, transesophageal and intra-cardiac ECG signals with novel LabVIEW software. Results: The analysis in the time domain evaluated fractionated atrial signals at the end of the signal averaged P-wave and fractionated ventricular signals at the end of the QRS complex. We evaluated atrial flutter in the time domain with two-to-one atrioventricular conduction, 212.0 ± 4.1 ms atrial cycle length, 426.0 ± 8.2 ms ventricular cycle length, 58.2 ± 1.8 ms P-wave duration, 119.6 ± 6.4 ms PQ duration, 103.0 ± 2.4 ms QRS duration and 296.4 ± 6.8 ms QT duration. The analysis in the frequency domain evaluated high frequency fractionated atrial signals during the P-wave and high frequency fractionated ventricular signals during QRS complex. Conclusions: Spectral analysis of signal averaging electrocardiography with novel LabVIEW software can be utilized to evaluate atrial and ventricular conduction delays in patients with atrial fibrillation and ventricular tachycardia. Complex fractionated atrial and ventricular electrocardiograms may be useful parameters to evaluate electrical cardiac bradycardia and tachycardia signals in atrial fibrillation and ventricular tachycardia ablation.

Jonas Tumampos, Matthias Heinke

A Clinico-Statistical Analysis of Writer’s Cramp Signals: Study with Indigenously Developed Multi-channel Intramuscular EMG

We investigated the hand muscles of Dystonia Writer’s cramp (WC) subjects affected due to DYT1 gene mutations in the brain. In clinical environments WC is done subjectively and lacking the objective. Therefore, the aim of the study is to determine if there is a quantifiable EMG difference in Writer’s Cramp (WC) patients with concordant mirror movements (MMs) from those with discordant MMs. For this, the five innocuous intramuscular microelectrodes (100 µ) are passed through five-muscles of intrinsic right-hand (RH). The EMG signals are acquired parallelly from five-muscles using indigenously built multi-channel EMG while subject writing with right-hand (RH), and with intrinsic left-hand. A canonical correlation-analysis between right-hand writing signal (RHWS) and left hand writing signals (LHWS) for each subject was carried out; giving squared canonical correlations. Correlations, for each subject between the signals when inscribing firstly with RH and then with LH are specified. Though, correlations are mostly negligible, albeit, some correlations are quite significant and distinctly high. These are presented as a Table of significant-correlations, i.e., correlations which are greater than 0.50 in absolute-value. It is found that often, the same muscle pairs will have significant correlation with same sign, in both ‘hand signals’ (i.e., RHWS, LHWS). In our computation, the scatter plot showed first two principal component (PC) scores explaining about 80% of variation. However, these findings are to be cross—validated with clinical findings on the same subjects.

Venkateshwarla Rama Raju

Classification of Myopotentials of Hand’s Motions to Control Applications

Realization of the system for classification of hand’s gestures is described in this paper. The first goal was to create hardware that would be able to measure signal of myopotentials for computer analysis without external noise and with right amplification. The second goal was to program an algorithm which could classify specific gestures of hand. Hardware prototype of four measuring channels was created by combination of 2nd order filters and right amount amplification. The user is isolated from the power source using galvanic isolation because of usage of active electrodes. For digitizing the data, the Arduino Nano microcontroller was selected and programmed using defined communication protocol. The computer software is programmed in C# programming language. Signal processing and drawing to user interface is in real time. The one of five possible gestures that user made is chosen using fuzzy logic and designed system of scaling.

Lukas Peter, Filip Maryncak, Antonino Proto, Martin Cerny

Quantitative EEG in Mild Cognitive Impairment and Alzheimer’s Disease by AR-Spectral and Multi-scale Entropy Analysis

To assist effective and precise diagnosis for mild cognitive impairment (MCI) and Alzheimer’s disease (AD), Electroencephalograph (EEG) has been widely used in clinical research of patients with AD at MCI state. To study the linear and nonlinear abnormality of EEG in AD and MCI patients, multiple characteristics was applied to distinguish AD and MCI patients from the normal controls (NC). EEG signals was recorded from 28 subjects, including 10 AD patients, 8 MCI subjects and 10 healthy elderly people. EEG signals in all channels was computed by auto-regressive model and multi scale entropy (MSE) to obtain relative power spectral density (PSD) value of each frequency band and entropy value in different time scales. Area under Receiver operating characteristic curve (AUC) was used to compare the classification ability of the two method. The ratio Alpha/theta of MCI group in left frontal area can distinguish MCI from NC subjects. Also the long scale entropy value in left frontal-central area manifests a better accuracy in distinguish AD and MCI from NC group. In addition, the combined feature from alpha/theta and long scale entropy in the left frontal central area can discriminate AD from NC group with higher AUC reaching 0.89. This indicated that combined PSD and MSE can be taken as a potential measure to detect AD in early state.

Xiaoke Chai, Xiaohong Weng, Zhimin Zhang, Yangting Lu, Guitong Liu, Haijun Niu

Analysis of Electroencephalographic Dynamic Functional Connectivity in Alzheimer’s Disease

The aim of this study was to characterize the dynamic functional connectivity of resting-state electroencephalographic (EEG) activity in Alzheimer’s disease (AD). The magnitude squared coherence (MSCOH) of 50 patients with dementia due to AD and 28 cognitively healthy controls was computed. MSCOH was estimated in epochs of 60 s subdivided in overlapping windows of different lengths (1, 2, 3, 5 and 10 s; 50% overlap). The effect of epoch length was tested on MSCOH and it was found that MSCOH stabilized at a window length of 3 s. We tested whether the MSCOH fluctuations observed reflected actual changes in functional connectivity by means of surrogate data testing, with the standard deviation of MSCOH chosen as the test statistic. The results showed that the variability of the measure could be due to dynamic functional connectivity. Furthermore, a significant reduction in the dynamic MSCOH connectivity of AD patients compared to controls was found in the delta (0–4 Hz) and beta-1 (13–30 Hz) bands. This indicated that AD patients show lesser variation in neural connectivity during resting state. Finally, a correlation between relative power and standard deviation was found, suggesting that an increase/peak in power spectrum could be a pre-requisite for dynamic functional connectivity in a specific frequency band.

Pablo Núñez, Jesús Poza, Carlos Gómez, Saúl J. Ruiz-Gómez, Víctor Rodríguez-González, Miguel Ángel Tola-Arribas, Mónica Cano, Roberto Hornero

Assessment of ECG Signal Quality After Compression

Highly efficient lossy compression algorithms for ECG signals are connected with distortion of the signals; lossy compression is a compromise between compression efficiency and signal quality. It is recommended to express this relation using rate-distortion curve. To decide whether the signal is suitable for further analysis, it is necessary to assess its quality after reconstruction. Although there exist many methods for quality assessment, neither of them is standardized or unified. The methods usually do not offer any information about their acceptable values. This paper introduces 10 new methods for signal quality assessment and their limits. Four methods are simple (entropy, mean, median, spectra similarity), two are based on delineation of ECG (SiP, SiPA), and four combine dynamic time warping, delineation, and calculation of distance (DTWdist, DTWpmfp1, DTWpmfp2, pmfp). These methods are tested on the whole standard CSE database using compression algorithm based on wavelet transform and set partitioning in hierarchical trees. The signals were compressed with various efficiency expressed by average value length (avL). Two ECG experts divided the compressed signals into three quality groups: perfect quality, good quality, not evaluable ECG. Owing to the experts’ ECG classification, we set the range of avL for each quality group. Based on this, we determined corresponding ranges of new methods’ values. Based on the trend of rate-distortion curve, its sensitivity, variability, their ratio at important boundary avL = 0.8 bps, and computational demand of the methods, we recommend four methods for further use.

Andrea Němcová, Martin Vítek, Lucie Maršánová, Radovan Smíšek, Lukáš Smital

Event-Related Synchronization/Desynchronization in Neural Oscillatory Changes Caused by Implicit Biases of Spatial Frequency in Electroencephalography

Spatial frequency may elicit characteristic mental and neural activity in humans, exhibiting a 1/f fluctuation. However, a visual pattern with only spatial frequency information will not necessarily explicitly affect any reaction, but may do so implicitly. We adopted an implicit association test (IAT), which is widely used in the research of implicit biases, to answer that question. At the same time, we attempted to characterize the neural activities associated with implicit spatial frequency biases by using electroencephalography (EEG). We used two types of checkered-pattern stimuli, high and low density, as targets. The high and low densities correspond to high and low spatial frequencies. There were two evaluative categories, with associated nouns and adjectives carrying a range of positive and negative meanings. EEG data were recorded, and the event-related synchronization (ERS) or desynchronization (ERD) for each event was analyzed based on the intertrial variances for the theta (4–7 Hz), alpha (8–13 Hz), low beta (13–20 Hz), high beta (20–30 Hz), and gamma (30–80 Hz) bands for each strong and weak associative strength comparison between targets. The category (e.g., high spatial frequency–positive or low spatial frequency–negative) was then obtained from the reaction times of the IAT for each subject. The ERS characteristics differed between strong and weak associative strengths, measured at the central areas at around 400–500 ms. This difference suggests that spatial frequency characteristics affect neural oscillatory activity associated with implicit biases of spatial frequency.

K. Kato, H. Kadokura, T. Kuroki, A. Ishikawa

Design and Development of Advanced Multi-channel EMG Micro Electrode Recording System

A new multi-channel EMG system with innocuous microelectrode recoding in the digitized form having a high sampling frequency going up to 6 kHz, maximum conversion of A/D converter 40 k samples/s was indigenously developed and installed at our NIMS tertiary care center in neurosciences millennium block (Hyderabad, India) with the department of neurology. Because of the limited computer system bus capacity of the interface, the sampling frequency of 6 kHz was provided for each channel. All 5 channels sampled simultaneously at 3 kHz. The continuous analogue signals while displayed on the 15 MHz frequency Oscilloscope (Philips maker dual tracer) were parallelly recorded online and stored digitally (using a 12 bit A/DC card (Dantec Dynamics maker, Denmark), embedded in Pentium computer. The EMG signals are acquired—recorded with a special reference to Writer’s cramp. The number of signal units in other words motor neurons in dominant intrinsic right hand is more than in the non dominant intrinsic left hand, and we found that there is a quantifiable difference between the two groups (concordant and discordant).

Venkateshwarla Rama Raju

Design of Linear Phase Filter by Using q-Bernstein Polynomial

The aim of this paper presents a design of IIR filter by using q-Bernstein polynomial. There are two parameters for adjusting a characteristic of frequency response. Stopband and slope of phase are adjusted by varying parameter $$ \varepsilon $$. The advantage is a linear phase and maximally flat more than Butterworth and Chebyshev. The stability can guarantee with Mihailov’s criterion.

Boonchana Purahong, Isoon Kanjanasurat, Vanvisa Chutchavong, Kanok Janchitrapongvej, Tuanjai Archevapanich

Analysis of Kinematic Parameters Relationships in Normal and Dysgraphic Children

Kinematic analysis of handwriting, using digital tablet together with appropriate tests and processing software, allows evaluation of subject graphomotor abilities. Several studies focused on the kinematic parameters extracted from the writing of both normal subjects and subjects with specific disorder, such as dysgraphia, recorded during simple tasks. However, relationships between these parameters have not yet been analyzed. The aim of this study was to examine and identify possible links between kinematic parameters like Amplitude (SA), Duration (SD) and Peak Velocity (PkVS) of Strokes extracted from handwriting and their changes between normal and dysgraphic children. Fifty normal and eighteen dysgraphic children, attending classes from 2nd to 5th grade of primary school, were involved in the study; three cursive tests were administered and analyzed. Results showed a linear relation between SA and PkVS parameters with a similar slope in both groups and reduced peak velocities in some dysgraphic children. A linear relationship was also present between SA and SD parameters in all tests for normal children while an unclear relation was found for dysgraphic children. The latter showed longer durations and slightly lower amplitudes than in normal subjects, in all tasks, as expected in case of poor fluency.

Diamante Morello, Milos Ajcevic, Iolanda Perrone, Agostino Accardo

Multiscale Analysis of Microvascular Blood Flow and Oxygenation

The purpose of this study is to investigate the feasibility of nonlinear methods for differentiating between haemodynamic steady states as a potential method of identifying microvascular dysfunction. As conventional nonlinear measures do not take into account the multiple time scales of the processes modulating microvascular function, here we evaluate the efficacy of multiscale analysis as a better discriminator of changes in microvascular health. We describe the basis and the implementation of the multiscale analysis of the microvascular blood flux (BF) and tissue oxygenation (OXY: oxyHb) signals recorded from the skin of 15 healthy male volunteers, age 29.2 ± 8.1y (mean ± SD), in two haemodynamic steady states at 33 °C and during warming at 43 °C to generate a local thermal hyperaemia (LTH). To investigate the influence of varying process time scales, multiscale analysis is employed on Sample entropy (MSE), to quantify signal regularity and Lempel and Ziv (MSLZ) and effort to compress (METC) complexity, to measure the randomness of the time series. Our findings show that there was a good discrimination in the multiscale indexes of both the BF (p = 0.001) and oxyHb (MSE, p = 0.002; METC and MSLZ, p < 0.001) signals between the two haemodynamic steady states, having the highest classification accuracy in oxyHb signals (MSE: 86.67%, MSLZ: 90.00% and METC: 93.33%). This study shows that “multiscale-based” analysis of blood flow and tissue oxygenation signals can identify different microvascular functional states and thus has potential for the clinical assessment and diagnosis of pathophysiological conditions.

Marjola Thanaj, Andrew J. Chipperfield, Geraldine F. Clough

Low- and High-Speed Arrivals Decomposition in 10–19 kHz Transmission Sounding of Human Lungs

The possibility of decomposition of received signals into high-speed (150–1000 m/s) and low-speed components (50–150 m/s) previously revealed is verified in independent sample. Four types of the ratio between the amplitudes of high- and low-speed arrivals and their changes depending on air-filling of lungs (inspiration/exhalation) are found. Only one of these types, representing predominance of amplitudes of high-speed arrivals, both during inspiration and exhalation is found in one elderly patient with a long-term course of hormone-dependent asthma, but not in 3 other young healthy volunteers. For medium frequency 15 kHz of the range low-speed arrivals velocities result in wavelengths between 0.33 and 1 cm. Such small wavelengths may provide the spatial resolution in lung parenchyma about the first centimeters. Thus transmission sounding of lungs in the range of 10–19 kHz seems promising to provide high-resolution acoustic imaging or may be even transmission tomography of pulmonary parenchyma.

Vladimir Korenbaum, Anton Shiryaev, Anatoly Kostiv, Maria Safronova

Analysis of Biological Response to Pleasure Elicited by Video

To study the objective evaluation of emotions, and pleasure in particular, biological responses to emotional videos were investigated. Fifteen adult males participated in the experiment. Five videos were used, which engendered “exhilaration,” “happiness,” “being comforted,” “disgust,” and “control.” Impedance plethysmography, electrocardiogram, photo plethysmography, continuous blood pressure, and respiration were measured and analyzed. Self-rated scores for “pleasure–displeasure” adequately varied among emotional-video stimuli. Biological changes were observed in the “exhilaration” condition, such as heart rate (HR), pulse wave amplitude, and pulse pressure. However, no biological changes in common were found among pleasurable emotions. To determine biological responses common to pleasurable emotions, the pulse wave was assessed in detail. Consequently, arterial compliance tended to decrease for each pleasurable emotion, albeit non-significantly. The maximum of the differentiated pulse wave (dP) changed significantly for “exhilaration” and “happiness.” Moreover, the combined parameter, which involved dP, HR, and mean blood pressure changed significantly for all pleasurable emotions.

Masaji Yamashita, Takeshi Aikawa, Masataka Kitama, Toru Yokoyama

Pulse Rate Variability Analysis to Enhance Oximetry as at-Home Alternative for Sleep Apnea Diagnosing

This study focuses on the at-home Sleep apnea-hypopnea syndrome (SAHS) severity estimation. Three percent oxygen desaturation index $$ (ODI_{3} ) $$ from nocturnal pulse-oximetry has been commonly evaluated as simplified alternative to polysomnography (PSG), the standard in-hospital diagnostic test. However, $$ ODI_{3} $$ has shown limited ability to detect SAHS as it only sums up information from desaturation events. Other physiological signs of SAHS can be found in respiratory and cardiac signals, providing additional helpful data to establish SAHS and its severity. Pulse rate variability time series (PRV), also derived from nocturnal oximetry, is considered a surrogate for heart rate variability, which provides both cardiac and respiratory information. In this study, 200 oximetric recordings obtained at patients home were involved, divided into training (50%) and test (50%) groups. $$ ODI_{3} $$ and PRV were obtained from them, the latter being characterized by the extraction of statistical features in time domain, as well as the spectral entropy from the commonly used very low (0–0.04 Hz.), low (0.04–0.15 Hz.), and high (0.15–0.4 Hz.) frequency bands. The $$ ODI_{3} $$ and PRV features were joined in a multi-layer perceptron artificial neural network (MLP), trained to estimate the apnea-hypopnea index (AHI), which is the PSG-derived parameter used to diagnose SAHS. Our results showed that single $$ ODI_{3} $$ rightly assigned 62.0% of the subjects from the test group into one out the four SAHS severity degrees, reaching 0.470 Cohens kappa, and 0.840 intra-class correlation coefficient (ICC) with the actual AHI (accuracies of 90.0, 88.0 and 82.0% in the increasing AHI cutoffs used to define SAHS severity). By contrast, our MLP model rightly assigned 75.0% of the subjects into their corresponding SAHS severity level, reaching 0.614 $$ \kappa $$ and 0.904 ICC (accuracies of 93.0, 88.0 and 90.0%). These results suggest that SAHS diagnosis could be accurately conducted at-patients home by combining $$ ODI_{3} $$ and PRV from nocturnal oximetry

Gonzalo C. Gutiérrez-Tobal, Daniel Álvarez, Fernando Vaquerizo-Villar, Verónica Barroso-García, Adrián Martín-Montero, Andrea Crespo, Félix del Campo, Roberto Hornero

Are Extensor Digitorum Brevis and Gastrocnemius Working Together? Surface EMG Analysis in Healthy Children

A relationship between intrinsic and extrinsic foot muscles is acknowledged during walking. Literature on foot-muscle recruitment in children is not very extensive. Purpose of the study was the surface-EMG-based evaluation of possible concomitant recruitment of intrinsic and extrinsic foot muscles during healthy-children walking. Gastrocnemius lateralis (GL) was analyzed as representative for extrinsic foot muscles (ankle plantar flexor). Extensor digitorum brevis (EDB) is one of the main intrinsic foot muscles, controlling foot movement and stability. In this study, EDB was considered as representative of foot muscles. Surface-EMG signals during 4-min walking trial were acquired in eight healthy school-age children (mean ± SD: age 8.3 ± 1.7 years; height 136 ± 8 cm; mass 30.9 ± 6.2 kg) to fulfill the goal of the study. Then, Statistical gait analysis, a recent methodology performing a statistical characterization of gait, was applied to process EMG data. An exceptional number of strides were analyzed to consider the expected variability (mean ± SD = 265 ± 30 strides for each child, nearly 2500 in total). The research was undertaken in compliance with ethical principles of Helsinki Declaration and approved by institutional expert committee. Results showed that EDB activity is localized in two separate regions of gait cycle: mid-stance (from 8.2 ± 7.0 to 50.3 ± 15.0% of gait cycle) and swing phase, from 73.8 ± 13.8 to 95.1 ± 4.7%. Main GL activity occurred in the same regions: mid-stance (from 5.7 ± 2.5 to 49.7 ± 4.6% of gait cycle) and swing phase, from 69.2 ± 18.7 to 95.4 ± 5.4%. These findings showed that regions of activity of EDB and GL were practically overlapped, suggesting that EDB and GL worked synergistically for foot and ankle-joint control in children walking, in a large percentage of strides. Present study produced novel data on the variability of the reciprocal role of EDB and GL during children walking, providing a deeper insight in mechanisms regulating ankle-foot stability.

Francesco Di Nardo, Annachiara Strazza, Michela Sara Palmieri, Alessandro Mengarelli, Stefano Cardarelli, Laura Burattini, Ornella Orsini, Federica Verdini, Antonio Bortone, Sandro Fioretti

A Time-Frequency Approach for the Assessment of Dynamic Muscle Co-contractions

Co-contraction is defined as the activity of agonist and antagonist muscles around a joint, enhancing stability and balance. The quantitative assessment of muscle co-contractions would be meaningful for deepening the comprehension of this physiological mechanism. Thus, the purpose of this work is to quantify muscle co-contraction using energy localization in time-frequency domain of sEMG signal during straight walking. To this purpose, sEMG from tibialis anterior (TA) and gastrocnemius lateralis (GL) and basographic signals were acquired in five healthy subjects during walking. Basographic signals were analyzed to quantify foot-floor contact. sEMG signals were processed using Wavelet Transform (WT) to identify muscular co-contractions, according to the following steps. Daubechies (order 4 with 6 levels of decomposition) was chosen as mother wavelet. A denoising algorithm based on Daubechies mother wavelet was applied for removing noise from raw signals. Denoised signals were decomposed into WT coefficients with different frequency content, and then recombined to achieve the co-scalogram function, a localized statistical assessment of cross-energy density between signals. The localization of regions with maximum cross-energy density provided the assessment of co-contractions in time-frequency domain. This methodology applied to TA and GL signals was able to detect GL/TA co-contractions during mid-stance (30–34% of GC) phase, matching with literature. Moreover, WT approach was able to provide also the frequency band of information content for muscle co-contractions: 65–164 Hz. In conclusion, this study proposed WT cross-energy density as a reliable estimation of muscle co-contraction in time-frequency domain.

Annachiara Strazza, Federica Verdini, Alessandro Mengarelli, Stefano Cardarelli, Laura Burattini, Sandro Fioretti, Francesco Di Nardo

Scalp Level Connectivity for Representative Channels in Emotional Status

Emotion can be regarded as a special brain status and it can be captured by Electroencephalography (EEG) via deploying number of channels all over the scalp. To find out the characteristics of emotional responses, the scalp level connectivity is one of the interests that considered. Nevertheless, to distinguish the significant EEG channels, which can imply the special regions at scalp level, has not yet been studied well. Therefore, in this work, we aim to identify the representative channels towards different emotional status by considering the connectivity derived from the values of coherence and correlation. In this purpose, DEAP, an online database has been investigated. Certainly, the emotional status can be evaluated on the valence-arousal (V-A) space and here, four groups contain HVHA, HVLA, LVHA, and LVLA have been studied. The results from 16 subjects show that the EEG channels AF3, F7, P7 and O1 have higher percentages in term of the connectivity and they could be considered as the representative channels in this case. Such findings could be useful to understand the scalp responses in emotional status.

Jia Wen Li, Xu Tong Cui, Shovan Barma, Sio Hang Pun, Pedro Antonio Mou, Hui Juan Huang, U. Kin Che, Mang I. Vai, Peng Un Mak

Investigation of Changes in Causality Throughout Life—A Magnetoencephalogram Study Using Granger Causality and Transfer Entropy

The use of magnetoencephalogram (MEG) signals in cognitive neuroscience research to investigate the functioning of the brain has increased over recent years. In this sensor space study, Granger Causality (GC) and Transfer entropy (TE) were applied to resting state MEGs from 220 healthy volunteers (aged 7–84) to characterise the possible changes in causality due to age and gender. Additionally, graph theory principles were used to evaluate different network components such as integration (global efficiency), segregation (clustering coefficient and modularity), centrality (betweenness), and resilience (strength and assortativity). Results showed that males had higher GC than females until mid-adulthood (~60 years). However, this gender difference was not observed using TE. Moreover, complex network analysis results of low global efficiency, high clustering coefficient, and low node strength, suggest that at rest, the brain topology resembled a network made up of loosely connected modules that had segregated and disassortative nodes with low resistance to change. Statistical analyses of results from both techniques, using pairwise t-test and two-way ANOVA, showed that age had a significant effect (p < 0.05) in all brain regions for both genders with significant gender differences being observed over the anterior, posterior, left lateral and right lateral regions of the brain. The results from this study could be used to develop a fingerprint of healthy ageing, which can potentially be used to assist with the identification of alterations to background brain activity due to pathology.

Elizabeth Shumbayawonda, Alberto Fernández, Michael P. Hughes, Daniel Abásolo

EEG Functional Connectivity Detects Seasonal Changes

Seasonal alterations in human health, mood, and basal cortisol level have been reported in several studies. Despite the interest in these factors, seasonal changes in brain functional connectivity as a possible base of these phenomena have not been studied before. The aim of the current study is to analyse seasonal effects using two resting electroencephalogram (EEG) functional connectivity measures: magnitude-squared coherence (MSC) and imaginary coherence (iCOH). Recordings from 80 healthy Estonians were used: 25 recordings from spring, 8 from summer, 10 from autumn and 37 from winter months. Eyes-closed resting EEG was recorded from 30 channels using Neuroscan Synamps2 acquisition system and five frequency bands were analysed: delta, theta, alpha, beta and gamma. Multivariate permutation test revealed significant influence of seasons on beta MSC. Furthermore, statistical analysis between different seasons showed increased beta MSC in spring and winter months compared to summer and autumn months, increased beta iCOH in spring, autumn and winter months compared to summer months and increased gamma MSC in spring and summer months compared to autumn months. The increase in beta MSC and iCOH in spring and winter months compared to summer months may be the result of increased stress or deficiency in Vitamin D. Current study is the first to bring out seasonal changes in brain functional connectivity, but the shortcoming of the study is the limited number of recordings in summer and autumn months. Therefore, further studies are required for more reliable results.

Laura Päeske, Maie Bachmann, Jaan Raik, Hiie Hinrikus

Influence of Dysgraphia on Kinematic Characteristics of Handwriting in Italian Primary School Children

Handwriting is a complex skill that improves with schooling and it is accomplished after the child has achieved and integrated underlying perceptual-motor performance components. Even though nowadays children are expected to acquire a level of handwriting proficiency, even on the first day of school, at least 27% of the school population has difficulty with handwriting and needs to be screened for (with) an intervention program. In this paper, we examined the influence of dysgraphia on kinematic characteristics of normal and dysgraphic Italian children from 2nd to 5th grade of primary school. Three cursive tasks (sequence of lelele and Accurate and Fast copy of a sentence) were proposed and several kinematic parameters were evaluated. Since differences were present among grades both in normal and dysgraphic children, each parameter was compared between children coming from corresponding grades by means of the Wilcoxon rank sum test. The main results showed significant differences between the two groups within each grade for curvilinear velocity, total length and number of letters per second. Pen-lift durations were significantly different only in the Accurate and Fast tasks while number of strokes per second as well as stroke duration and length showed significant differences depending on the task and grade. These differences support the hypothesis of a lower fluency and automation as well as a different motor planning in dysgraphic subjects. Finally, many kinematic parameters could be useful for an early identification of dysgraphia in order to activate an immediate rehabilitative treatment.

Giulia Silveri, Federica De Dea, Iolanda Perrone, Agostino Accardo

Power Spectral Density Analysis in Spindles Epochs in Healthy Children

Sleep spindles are important components of the N-REM stage-2 in the sleep electroencephalogram (EEG). They are oscillatory EEG activities of fusiform morphology in the range of 10–16 Hz [1], and a duration between 0.5 and 3 s. Spindles have been associated with cognitive skills and sleep-dependent memory consolidation. The aim of this study is to assess differences in the before (“pre”), during (“dur”) and after (“post”) spindle epochs by means of main power spectral bands delta (2–4 Hz), theta (4–8 Hz), alpha (8–12 Hz), beta (12–30 Hz), gamma (30–44 Hz), total (2–44 Hz) and sigma bands (12–16 Hz), calculated by the Welch periodogram, and by Fractal dimension (FD). The analysis was carried out on 7 healthy children (mean age = 8.90 ± 1.34 years) deprived of sleep on the day of the acquisition to enhance the deep sleep during the recording. For each EEG record (standard 10–20, 19 electrodes, sampling rate 512 Hz), two neurophysiologists labeled the start and the end points of the three sleep epochs. The results showed statistical differences between “dur” and both “pre” and “post” epochs in almost all channels (except O1 and O2) for all bands, except gamma. Furthermore, the values of FD were significantly different between “dur” and both “pre” and “post” epochs, for all channels. The FD values in “dur” epochs were smaller than in both “pre” and “post” ones, showing a lower EEG complexity during spindles, compared with the “pre” and “post” epochs. FD values in “post” epochs were found similar to those in “pre” periods. These differences could be useful to comprehend the spindles changes during sleep time. Moreover, these data could help on understanding the system generator of the spindles.

Federica De Dea, Caterina Zanus, Marco Carrozzi, Matteo Stecca, Agostino Accardo

RF Ultrasound Based Longitudinal Motion Estimation of Carotid Artery Wall: Feasibility Study

Arteriosclerosis is a chronic, systemic, inflammatory disease of arteries. Arteriosclerosis reveals itself when complications when as constricted artery lumen and (or) its thrombosis, enlarged and thinner wall (aneurysm) build up. Nonetheless, it has been proved than significant changes of the mechanical properties of common carotid artery (CCA) wall are present much earlier than the anatomical changes appear. The aim of this work is to propose and evaluate an algorithm for analysis of longitudinal and radial movements of CCA wall from registered radiofrequency (RF) ultrasound (US) signals. The proposed method uses RF US signals, phase correlation and sub-sample algorithm to estimate radial and longitudinal movements of CCA wall which was monitored continuously for four cardiac cycles. A physical phantom and in vivo test were employed for testing the algorithm. The results with phantom show that a normalized root mean square error (NRMSE) of detected motion amplitude is from 0.21 to 0.41 μm and the coefficient of correlation is from 0.95 to 0.98 in case of any determined longitudinal motion function when the phase correlation, sub-pixel algorithm and additional filtering were used. The results from this validation study demonstrate the feasibility of CCA longitudinal and radial movement assessment in vivo using phase correlation and sub-sample algorithm. Radiofrequency ultrasound signals algorithm could be used to characterize radial and longitudinal displacements in early stage arteriosclerotic artery.

Monika Zambacevičienė, Rytis Jurkonis

Models of Physiological Parameters for Runners and Cyclists

The study of physiological parameters dynamic is currently the main area of research in exercise physiology. The most common physiological data to collect include heart rate, oxygen saturation, core body and skin temperature, blood pressure, ECG, oxygen consumption and others. The data obtained are often related to various forms and intensities of physical activity, and in accordance with the principles of personalized medicine evaluated. Mathematical models are able to simulate some physiological parameters e.g. heart rate, oxygen consumption etc. during cycling exercise on bicycle ergometer or running exercise on treadmill. Workload intensity (in Watts) on bicycle ergometer and running velocity (in km/h) on the treadmill are taken as input for dynamic models. Determination of dynamic models of physiological parameters is fundamental for athletic training methodology, as well as evaluation of cardiorespiratory capacity and fitness. The present work demonstrates the application of dynamic systems models to the simulation of heart rate kinetics and oxygen consumption during workloads of time-varying intensity. Optimization of free model parameters could be used as important information about the health condition of the subject with special reference to the cardiorespiratory capacity and fitness age. The models could be used both for athletes as well as for untrained sedentary population.

Milan Stork, Jaroslav Novak, Vaclav Zeman

Cyclostationary Analysis of Respiratory Signals with Application of Rate Determination

Respiratory signals are periodic-like signals where the noisy periodic pattern repeats itself. Therefore, based on a stationarity assumption, autocorrelation function contains noisy cycles in time-lag with the same rate as the respiration rate. In this work, cyclostationarity test is performed on the respiratory signals in order to determine cyclic characteristics of the time varying autocorrelation function. Our specific aim is to check whether the cycle period in time corresponds to the respiration rate. Lung simulator was used to generate the respiratory signals. Time varying autocorrelation variance was computed by using both the modified windowed, and the blocked signal methods. Our simulations resulted that the cycle period was the same as the respiration period. Moreover, we observed that cyclic frequencies corresponded to the respiratory rate and its harmonics.

Esra Saatci, Ertugrul Saatci, Aydin Akan

A New Approach for Brain Source Position Estimation Based on the Eigenvalues of the EEG Sensors Spatial Covariance Matrix

Direction of Arrival (DOA) estimation methods, like MUSIC, can be applied to EEG signals for brain source localization. However, they show a severe degradation at small signal-to-noise ratios on the EEG sensors and for large amounts of brain sources. Inspired on the SEAD method, this article introduces a new method that analyses the eigenvalues of a modified spatial covariance matrix of the EEG signals to produce a two-dimensional spectrum whose peaks more robustly estimate the source positions on a horizontal section of the brain. The key approach is to select the eigenvalues that are less affected by the noise and use them to produce the spectrum. To assess the accuracy and robustness of the proposed method, we compared its root-mean-square-error performance at different noise conditions to those of MUSIC and NSF. The proposed method showed the lowest estimation errors for different amounts of brain sources and grid densities.

Lucas F. Cruz, Marcela G. Magalhães, Jonas A. Kunzler, André A. S. Coelho, Rodrigo P. Lemos

Discrimination Between Day and Night ECG Recordings Based on the Morphology of P and T Waves

This paper investigates the possibility to discriminate day-night periods based exclusively on morphological characteristics extracted from $$ P $$ and $$ T $$ waves. Daytime values were determined between 13:00 and 15:00 and nighttime values between 1:00 and 3:00. Initially, $$ P $$ and $$ T $$ waves were selected manually and afterwards in an automatic way, employing a new algorithm. After delimiting the position of $$ P $$ and $$ T $$ waves, thirty four features, most of which employed for the first time for this purpose, were extracted using geometrical measures. All these features were examined for both waves. The results revealed a very clear discrimination for the majority of the features, leading to the conclusion that $$ P $$ and $$ T $$ wave morphology is very different during day and night, whilst the correlation coefficient indicated an association and not an arbitrary alteration. Despite the fact that the selected features were rich descriptors, machine learning techniques were also employed to confirm the discrimination capability.

Dimitrios Zavantis, Ermioni Mastora, Prokopis Kontogiannis, George Manis

Automated Neurons Recognition and Sorting for Diamond Based Microelectrode Arrays Recording: A Feasibility Study

Microelectrode arrays (MEA) are extensively used for recording and stimulating neural activity in vitro and in vivo. Depositing nanostructured boron doped diamond (BDD) onto the neuroelectrodes makes it possible to obtain dual mode low-noise neuroelectrical and neurochemical information simultaneously. The signal processing procedure requires finding and distinguishing individual neurons spikes in the recordings. Spike identification is usually done manually which is inaccurate and inappropriate for complex datasets. In this paper, we present a methodology and two algorithms for neurons recognition and evaluation based on unsupervised learning. Forty-five extracellular randomly selected signals from 26 unique measurements of embryonic hippocampal rat neurons (20 kHz, 6 min) were recorded on the commercial 60 TiN channels MEA. The signals were filtered in the 300–3000 Hz band and an amplitude detector (4x std of the background noise) was used for spike detection. WaveClus features were computed and its 3 PCA components were extracted for every spike. The optimal number of clusters were evaluated by an expert rater. K-means + gap criterion (alg. 1) and the Gaussian Mixture Model + Bayesian Information Criterion (alg. 2) were implemented and compared. The total IntraClass Correlation showed a significant inter-rater agreement for all 3 rater procedures (ICC = 0.69, p < 0.001), when post hoc weighted Cohen’s Kappas for 2 raters were 0.85 (expert vs. alg. 1; p < 0.001) and 0.62 (expert vs. alg. 2; p < 0.001). This will contribute to the objective definition of dual mode BDD MEA performance criteria and for a comparison with the current system.

Ondřej Klempíř, Radim Krupička, Vladimíra Petráková, Jan Krůšek, Ivan Dittert, Andrew Taylor

Ultra-Short Entropy for Mental Stress Detection

Approximate Entropy (ApEn) and Sample Entropy (SampEn) are measures of signals’ complexity and are widely used in Heart Rate Variability (HRV) analysis. In particular, recent studies proved that almost all the features measuring complexity of RR series statistically decreased during the stress and therefore, thus showing ability to detect stress. However, the choice of the similarity threshold r and minimum data length N required for their computation are still controversial. In fact, most entropy measures are considered not reliable for recordings shorter than 5 min and different threshold values r have shown to affect the analysis thus leading to incorrect conclusions. Therefore, the aim of this study was to understand the impact of changing parameters r and N for the computation of ApEn and SampEn and to select the optimal parameters to detect stress in healthy subjects. To accomplish it, 84 RR series, extracted from electrocardiography signals acquired during real-life stress, were analyzed. ApEn and SampEn were estimated for two different values of r computed using previously published methods and for N = {100, 200, 300, 400, 500} data points. The statistical significance for the differences in mean ApEn and SampEn values was assessed by non-parametric tests. The two methods used to compute r produced entropy values significantly different over different N values. In contrast, ApEn and SampEn showed consistency in differentiating rest and stress conditions for different input parameters. More specifically, ApEnChon and SampEn Chon showed to have a better discrimination power between stressed subjects and resting subjects on ultra-short recordings (N < 500).

Rossana Castaldo, Luis Montesinos, Leandro Pecchia

Assessment of In-ear Photoplethysmography as a Surrogate for Electrocardiography in Heart Rate Variability Analysis

Heart rate variability (HRV) analysis is a valuable tool in the investigation of cardiovascular regulation by the autonomic nervous system. Generally, beat-to-beat interval time series, which are necessary for calculating quantitative HRV parameters, are extracted from electrocardiographic (ECG) recordings. However, in situations like home monitoring, acute medical care or the perioperative setting, the recording of ECG signals is inconvenient. Here, in-ear photoplethysmography (PPG) is a promising alternative technology for the acquisition of beat-to-beat intervals. In this work, the accuracy of HRV parameters derived from in-ear PPG recordings is compared to ECG-derived parameters in order to the accuracy of the in-ear PPG as a surrogate for ECG in HRV analysis. For this purpose, recordings of 28 volunteers were collected. Common HRV features from both the time and frequency domain have been calculated from the in-ear PPG signal and a reference ECG signal. For comparison, HRV parameters were also derived from the common fingertip PPG. It could be shown that the in-ear PPG is a viable alternative measurement modality for continuous HRV monitoring when ECG recording is not applicable. Nevertheless, care has to be taken in the selection of HRV parameters that are calculated from the in-ear PPG.

Timo Tigges, Thomas Büchler, Alexandru Pielmuş, Michael Klum, Aarne Feldheiser, Oliver Hunsicker, Reinhold Orglmeister

Statistical Guideline of Threshold Determination for Cardiac Spiral Wave Center Detection Using Phase Variance Analysis

Spiral wave (SW) plays a key role in generation and termination of fatal tachyarrhythmia. In our previous study, we proposed a novel objective tracking method of SW center trajectories by using phase variance (PV) analysis. This method evaluates local variance of phase values around each point to detect the position of SW center as the peak of PV map. PV analysis improved the detection accuracy of meandering SW centers and complex multiple SW centers significantly. However, the algorithm still includes some hyperparameters, the window size for the evaluation of phase variance and the binarization threshold for the peak detection. Thus, some guideline for proper determination of those parameters has been required. In this study, we hypothesized that the appropriate binarization threshold depends on the window size, and it can be determined as the level of PV value with specific p-value on Rayleigh’s test. We compared the detection results with various window sizes (3, 6, 9, 12 pixels) and various thresholds (from 0.4 to 0.9). Optical mapping measurement data with single SW center and four SW centers were evaluated. As a result, proper numbers of SW centers were detected with the thresholds corresponding to the p-value of 0.05, even with the smallest window size (3 pixels). From these results, it was indicated that the suggested method based on Rayleigh’s test is valuable for proper determination of PV analysis parameters.

Naoki Tomii, Masatoshi Yamazaki, Nitaro Shibata, Haruo Honjo, Ichiro Sakuma

A Brain Connectivity Metric Based on Phase Linearity Measurement

The analysis of brain connectivity is gaining interest in recent years due to the relevant information it carries about the functioning of the brain in health and in disease. In brief, it consists in measuring the statistical dependencies between signals generated by different brain regions. Several metrics have been proposed in literature, related to three families: amplitude based, phase based on jointly amplitude and phase based. Due to the large amount of noise that typically affects the estimation of the connectivity maps, averaging over several epochs of a population is normally carried out. We propose a novel phase based metric, namely the Phase Linearity Metric (PLM), that is resilient to noise and volume conduction, bearing promise to lower the number of epochs needed for a reliable measurement. The comparison with the widely adopted PLI connectivity metric confirms the effectiveness of the PLM.

Fabio Baselice, Antonietta Sorriso, Rosaria Rucco, Pierpaolo Sorrentino

Modeling of the Microvascular Pulse for Tracking the Vasoconstriction Response to Deep Inspiratory Gasp

This work demonstrates the suitability of a microvascular pulse decomposition algorithm (PDA) for evaluating the vasoconstriction response to a deep inspiratory gasp (DIG). Synchronous ECG, respiratory, and laser Doppler flowmetry (LDF) signals of 13 healthy subjects (age: 26 $$ \pm $$ 3 years) were analyzed, and a four-Gaussian PDA was applied to reconstruct the LDF heartbeat pulsations. To assess the tracking of the transient vasoconstriction, the goodness-of-fit achieved during the DIG was compared with the performance at baseline. Moreover, the heart rate (HR) derived from the model’s systolic component was validated against the ECG, comparing the agreement with the one obtained from the wavelet transform analysis (WTA) of the LDF signal. The model’s normalized root-mean-square error and average $$ {\text{R}}^{2} $$ did not decrease during the DIG (p = 0.249, p = 0.552), and a nearly optimal pulse modeling accuracy was maintained (p = 0.286). Furthermore, the proposed PDA could better reproduce the reference HR than WTA, with a 46.8% reduction of the median root-mean-square error (p < 0.001), which did not worsen during the DIG (p = 0.861). Therefore, this method might find valuable application in the evaluation of neurovascular deterioration.

Michele Sorelli, Antonia Perrella, Leonardo Bocchi

Wavelet Phase Coherence Between the Microvascular Pulse Contour and the Respiratory Activity

A wavelet phase coherence (WPC) analysis was conducted in order to evaluate the time-phase relationships between the respiratory activity and the pulse of the peripheral perfusion. The investigation involved a group of 21 young healthy subjects, aged from 20 to 30 years. Cutaneous perfusion was measured by laser Doppler flowmetry, while breathing was simultaneously monitored with a wearable chest band. A multi-Gaussian modeling algorithm was used to decompose the pulse waveform thus enabling the separate characterization of the forward-travelling systolic pulse and the diastolic components arising from vascular impedance mismatch. The WPC between model-derived shape features and the breathing rhythm was assessed, to determine whether their characteristic oscillations were somehow synchronized. In 17 subjects a significant degree of phase coherence was detected in the respiratory frequency band for the area beneath the diastolic phase of the cardiac pulse. This result indicates that the microvascular reflection waves exhibit a marked periodicity linked to the breathing activity.

Antonia Perrella, Michele Sorelli, Francesco Giardini, Lorenzo Frassineti, Piergiorgio Francia, Leonardo Bocchi

Selection of Entropy-Measure Parameters for Force Plate-Based Human Balance Evaluation

Human balance is commonly evaluated through the center of pressure (COP) displacement measured with a force plate, producing 2D time-series that represent COP trajectories in the anteroposterior and mediolateral directions. Entropy measures have been previously used to quantify the regularity of those time-series in different groups and/or experimental conditions. However, these measures are computed using multiple input parameters, the selection of which has been scarcely investigated within this context. This study aimed to investigate the behavior of COP time-series entropy measures using different parameters values, in order to inform their selection. Specifically, we investigated Approximate Entropy (ApEn) and Sample Entropy (SampEn), which are very sensitive to their input parameters: m (embedding dimension), r (tolerance) and N (length of data). A dataset containing COP time-series for 159 subjects with no physical disabilities was used. As a case study, subjects were grouped in young adults (age < 60, n = 85), and older adults (age ≥ 60) with (n = 18) and without (n = 56) history of falls. ApEn and SampEn were computed for m = {2, 3} and r = {0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5} with a fixed data length (N = 1200 points). ApEn and SampEn values were compared between groups using one-way ANOVA. Our results suggest that ApEn and SampEn are able to discriminate with ease between young and older adults for a wide range of m and r values. However, the selection becomes critical for the discrimination between non-fallers and fallers. An m = 2 and r = {0.4, 0.45} are suggested in this case.

Luis Montesinos, Rossana Castaldo, Leandro Pecchia

Assessment of Similarity Between Finger and Wrist Photoplethysmography According to the Light Wavelength

The purpose of this paper is to investigate optimal measurement site of wrist PPG by comparing wrist PPG with conventional finger PPG in terms of pulse quality index (PQI). PPGs are obtained from left index finger and five specific sites around the wrist during 40 s with multiple wavelengths; green (530 nm) and infrared (960 nm). To evaluate the PQI, we calculated PQI using existing PQI metrics such as perfusion index (PI), zero crossing rate (ZCR) in every pulse of PPG. As a result, in PQIPI, significant differences (P < 0.05) were found between finger PPG and wrist PPG in all measuring position. On the other hand, in PQIzcr, no significant differences were founded in all measuring site on wrist in case of infrared PPG.

Sangjin Han, Hangsik Shin

EEG Coherence Analysis in Subjects After Rehabilitation from Stroke with Motor Imagery

Stroke is caused by a lack of blood supply in a particular region of the brain that may be a consequence of clot formation or rupture of the blood vessel. It presents high incidence, generating permanent neurological sequelae, which leads to motor impairment and functional limitations. It is necessary to identify techniques of motor rehabilitation that favour the cortical reorganization and the functional recovery of affected individuals. Motor imagery (MI) is a technique used in motor rehabilitation of individuals with motor deficit, defined as mental simulation of movements without movement actually occurring. MI activates the same cortical regions as the execution of the movement, especially the motor area and the somatosensory cortex. The objective of this study was to investigate changes in cortical activity related to MI rehabilitation (during 1 month—three session/week) in hemiparetic individuals after stroke. EEG signals from eight post-stroke individuals were registered one week before MI rehabilitation (BMI) and 1 month after rehabilitation (Follow-up), during motor task execution (MOV) and motor task imagination (IMG). Magnitude squared of coherence (MSC) was evaluated, using 50 epochs of the EEG signal considered without artefact. The delta band presented the highest MSC values in both conditions (MOV and IMG), mainly in frontal and central regions. Only two volunteers presented MSC values in the Follow-up period higher than in the period before mental rehabilitation, mainly on electrodes F3 (p = 0.04), C3 (p = 0.036) and F4 (p = 0.02).

L. C. P. da Silva, C. C. S. C. Paz, A. M. F. L. Miranda de Sá, C. J. Tierra-Criollo

Optimal Window for the Estimation of Very Low Frequency Content in Heart Rate Variability Analysis

The spectral analysis of heart rate variability (HRV) is an accepted method for assessing the autonomic control of the cardiovascular system. The electrocardiographic recordings used to extract the time interval between consecutive R waves (RR intervals or tachogram) should last 5 min or 24 h, according to the guidelines published in 1996 by the European Heart Journal (TASK FORCE). The three frequency bands recognized are the VLF (0.003–0.04 Hz), the LF (0.04–0.15 Hz) and the HF (0.15–0.4 Hz), which are associated with cardiovascular modulatory mechanisms. Given that the estimation of VLF in 5 min recordings is unreliable and that in some circumstances (orthostatism, controlled breathing, etc.) it is not possible to obtain 24 h recordings, it becomes necessary to consider other window sizes in order to estimate it with greater certainty. To show how the size of the window affects the estimation of the power spectral density, synthetic signals were evaluated using the Welch periodogram, comparing the power and spectral resolution obtained with conventional 5 min windows versus results obtained with windows that ranged from 300 to 3000 s in steps of 300 s, plus an additional one of 4000 s. Noise-free signals were generated, contaminated with White Gaussian Noise and mounted on a linear trend, to approximate the conditions of a real tachogram. The results suggest that the optimal size of the analysis window is 50 min, decreasing the power estimation error of the VLF band from 24.91 to 8.06%, increasing the spectral resolution and increasing the confidence in the evaluation of the three frequency bands defined for the HRV, especially for the VLF. These results suggest an alternative analysis for recordings with duration less than 24 h but that require evaluating the VLF, as in the HRV recordings of patients during their haemodialysis session.

B. Becerra-Luna, R. Martínez-Memije, R. Cartas-Rosado, O. Infante-Vázquez, J. C. Sánchez-García, G. Sánchez-Pérez

Optimization of Algorithms for Real-Time ECG Beats Classification

Beats classification is an essential step in the ECG signal analysis for cardiac arrhythmias detection. There are multiple alternatives to solve this problem, but these are considerably reduced when real-time restrictions are added to the analysis. The goal of this work is to expose an optimal solution based mainly on the use of voltage values of the signal in the time domain and compare it with other based on Daubechies’ Wavelets analysis. Several measures are used in both feature spaces to determine the similarity of every beat to a patient’s specific patterns and, after that, a method similar to clustering’s algorithms is used to assign a class to each. To evaluate the performance of the proposed algorithms, ECG signal records extracted from the MIT-BIH database are used. With the method used in the analysis, we obtained 93.25% of sensitivity and 91.43% on premature ventricular contractions predictivity, which allow us to conclude that it is very feasible for their application in real time systems, due to their low computational cost.

Rolando González Tejeda, Maité Cañizares Falcón

Wave Kurtosis: A Novel, Specific Parameter for TUG-Turn Quantification

The Timed Up and Go test (TUG) is widely used in both research and clinical settings. The most common parameter for quantification of functional decline is the duration of a performed TUG. Analysis of the turn part of the TUG could provide valuable information about functional decline. Notwithstanding, there are only a few studies that deals with the TUG turn processing. This study proposes a novelty parameter—wave kurtosis (WK) that provides quantitative metrics for describing and comparing turn patterns. The WK is designed to evaluate the shape of the signal waveform. The WK quantifies the peak of the signal, its position and tails. The TUG-turn angular rate was analysed. Intra-class correlations (ICC) of WK and the strength of a linear association between WK and established turn parameters (turn duration, peak angular rate, and mean angular rate) were calculated. The reliability of WK about the vertical axis was moderate (ICC > 0.50), while reliabilities of the frontal axis and sagittal axis varied according to the subject group. The WK about the vertical axis was moderately correlated with turn duration, mean value and peak value. Utilization of waveform parameters opens a new area of TUG turn analysis and may allow for a more sensitive determination of movement disorders or fall risk assessment. Therefore, future studies utilizing turn movement may benefit from the use of the wave kurtosis.

Slavka Viteckova, Radim Krupicka, Patrik Kutilek, Vaclav Cejka, Zoltan Szabo, Martina Hoskovcova, Evzen Ruzicka

Investigation of the Feasibility of Postoperative Pain Assessment Using Frequency Analysis of Photoplethysmogram Variability

Quantifying of pain is necessary for optimal dose of opioid. In pain quantification, there have been many attempts to analyze the photoplethysmography (PPG) waveform as a promising maker of autonomic function. In this paper, we investigate the feasibility of PPG amplitude variability (PPGV) as a novel marker of pain quantification. We derived 8 parameters related to the PPG amplitude and amplitude variability: ACAbaseline, ACAdia, PPGAVsys, PPGAVdia, PPGAVsys/ACAbaseline, PPGAVsys/ACAdia, PPGAVdia/ACAbaseline and PPGAVdia/ACAdia, and calculated frequency domain variables, TP, VLF, LF, HF, nLF, nHF and LF/HF, that have been used for heart rate variability analysis. Every parameter was derived in clinical dataset obtained before and after surgery, and a significant difference was statistically verified using paired t-test. Consequently, a significant difference (p < 0.05) was found in every derived variable except for most variables in ACAbaseline, ACAdia, PPGAVsys, PPGVdia, in nHF of PPGAVsys/ACAbaseline, in nHF, LF/HF of PPGAVsys/ACAdia, in nLF, nHF of PPGAVdia/ACAdia, and in nLF, nHF of PPGAVdia/ACAbaseline. This result suggests that the possibility of frequency domain analysis of PPGV as a novel indicator of surgical pain quantification.

Yoon La Yang, Hyeon Seok Seok, Hangsik Shin

A Decision-Making Fusion Method for Accurately Locating QRS Complexes from the Multiple QRS Detectors

QRS detection for electrocardiogram (ECG) signal plays a fundamental role in monitoring cardiovascular diseases. Lots of QRS detection algorithms exist and most of them are verified with high sensitivity and positive predictivity on the standard ECG databases. Recent progress in mobile ECG rises the challenge of accurate QRS detection for real-time dynamic ECG recordings since the variety of noises. In this study, a decision-making fusion method for accurately locating QRS complexes from the multiple QRS detectors were proposed. First, the ECG signals were detected by these nine detectors. Then, the voting fusion rule had been established that a heartbeat was determined when more than five detectors showed their detections in a time moving window respectively. And the mean value of the middle three detections’ positions in the window was served as a corrected heartbeat. Moreover, the comprehensive post processing technology was used to eliminate the false detection and to search the missed beats. The new proposed method was tested on high and poor signal quality ECG databases. For comparison, the best detection accuracy for the single algorithm was only 75.50% while the new proposed fusion method with 200 ms time moving window reported a detection accuracy of 80.43% for the poor-quality ECG signals. The proposed fusion method can significantly improve locating QRS complexes accuracy for the ECG signals with poor signal quality. Thus, it has a potential usefulness in the real-time dynamic ECG monitoring situations.

Feifei Liu, Chengyu Liu, Xinge Jiang, Lina Zhao, Jianqing Li, Chuanjie Song, Shoushui Wei

Effect of Myocardial Infarction Size on the Simulated ECG Morphology Based on a 3D Torso-Heart Model

Objective: Myocardial infarction (MI) is a big threat to human health. Underlying linkage between changes in standard electrocardiography (ECG) waveforms and different MI conditions is important. A three-dimensional (3D) bidomain torso-heart model was proposed for stimulating the MI effect. In this study, we aimed to quantify the effect of MI size on the simulated ECG morphology from this model. Methods: Using a simplified 3D torso-heart model, the electrical activation of heart and its conduction were simulated. The adopted 3D torso-heart model consists of torso, lung, and the whole heart components, including atria, ventricles, and blood chambers. Simulation of MI was performed by changing the control parameters of the infarcted region. All infarcts were located in the anterior wall of the left ventricle. The effect of MI size (three sizes: 168.1, 914.8 and 2,210 mm3) on the QRS complex from the stimulated standard 12-lead ECGs was explored. Results: The results demonstrated the progressions of heart depolarization and repolarization and revealed the difference of electrical conduction between the normal and MI hearts. Compared with Q-wave amplitude ratios (QARs) and S-wave amplitude ratios (SARs), the R-wave amplitude ratios (RARs) showed their superiority in the distinguish of lesion size, as they are in sequential order with the lesion size. However, the cooperation of QARs and SARs can also help determine the size of infarcted myocardium, especially in the chest ECG leads. Significance: This study provided a quantitative analysis for the effect of MI size on the simulated standard 12-lead ECG morphology. The simulated results confirmed the changes in ECG QRS complex due to the MI changes are consistent with the clinical futures. Thus, it provides an alternative tool for understanding the inherent conduction mechanism of ECG signal.

Zhipeng Cai, Jianqing Li, Kan Luo, Zhigang Wang, Xiangyu Zhang, Jian Zhang, Chengyu Liu

Effect of Ectopic Beats on Heart Rate Variability Indices in Heart Failure Patients

Heart rate variability (HRV) provides a valuable tool for early detection of cardiovascular abnormalities. Ectopic beats have been proven to have an influence on HRV results, but the effect of different amount of ectopic beats on analysis of congestive heart failure (CHF) patient rhythms has not been quantified. In this study, we tested the commonly used HRV indices for significant differences between 5-min RR segments with and without ectopic beats. Eight long-term CHF RR interval recordings from http://www.physionet.org were studied. Each recording was divided into non-overlapping segments of 5-min RR segments without or with different numbers of ectopic beats. Two time-domain HRV indices of SDNN and RMSSD and two frequency-domain indices of normalized low frequency (LFn) and high frequency (HFn) powers were employed. Results showed that ectopic segments had significantly larger values for SDNN (39 ± 18 vs. ectopic free segments 28 ± 16 ms, P < 0.05), RMSSD (47 ± 29 vs. 24 ± 23 ms, P < 0.05) and HFn (0.66 ± 0.13 vs. 0.52 ± 0.14, P < 0.01), and significantly lower values for LFn (0.34 ± 0.13 vs. ectopic free segments 0.48 ± 0.14, P < 0.01). Compared with the indices of RMSSD and frequency-domain indices, SDNN was least affected by a relatively small amount of ectopic beats (one to six beats). Compared with the time-domain indices, the frequency-domain indices responded more quickly to the appearance of ectopic beats.

Chengyu Liu, Lina Zhao, Zhipeng Cai, Feifei Liu, Yaowei Li, Shoushui Wei, Jianqing Li, Alan Murray

Heart Rate Monitoring for the Detection of Changes in Mental Demands During Computer Work

The detection of variations in mental demands is a key factor for optimizing the balance between occupational health and work performance. With the advances in heart rate acquisition technologies, heart rate monitoring is now easy and affordable. In this study, we recorded the heart rate of 18 healthy young participants while they performed three consecutive 5-min cyclic computer tasks with low, medium and high mental demands in two days with at least one week apart. The cycles began with memorizing a pattern of connected points following by the disappearance of the pattern, and then replicating it using computer mouse clicks on an incomplete version of the pattern. The mental demand of the tasks was manipulated by changing the complexity of the displayed patterns. The participants rated their perceived mental load after each task. The mean, range, and standard deviation of heart rate, MHR, RHR, and SDHR respectively, along with the performance (in terms of accuracy and speed of pattern replication) for each cycle was calculated and averaged for each task. The RHR and SDHR increased with increasing mental demands (p < 0.001), whereas the MHR did not significantly change in response to the different task demands. The responses remained consistent across days for RHR, MHR, but not SDHR. As expected, the performance decreased and the perceived mental load increased as the task demands increased. These results suggest that the variations in heart rate would provide useful information regarding the quantification of mental load.

Ramtin Zargari Marandi, Pascal Madeleine, Nicolas Vuillerme, Afshin Samani

Indirect Cardiac Output and Stroke Volume Assessment During Spiroergometric Examination

Cardiac output can be accurately estimated from VO2 (oxygen consumption) during exercise in normal subjects and in patients with heart failure by measuring the LAT (lactate acidosis threshold) or VO2peak (peak oxygen consumption) during bicycle ergometer test. Hence, during step-vice increased workload on bicycle ergometer with continuous measurement of oxygen consumption changes in cardiac output and stroke volume (SV) can be calculated. Our measurement documented usefulness of this method in subjects of different performance level, both men and women. Non-invasive evaluation of cardiac output and stroke volume during spiroergometric stress test enables to extent the information about the health status of the subject and about the functional reserve of his circulatory apparatus. The examples presented in this study prove the applicability of this method in evaluation of fitness level in healthy male and female subjects of different age. The data of cardiac output and stroke volume will be added into the software program of final protocol of complex sports medical examination. This method can enrich the scale of parameters testifying the functional capacity of the subjects.

Jaroslav Novak, Milan Stork, Vaclav Zeman

An Impulsive Noise Rejection Filter for Wearable ECG Signal Processing

Objective: QRS detection is essential for ECG signal processing. For real-time dynamic ECG, QRS detection is usually performed on a fixed time window, lengths from several to dozens of seconds. However, the unexpected impulsive noise (usually short-term but large amplitude) within the ECG episode is a disaster for QRS detectors. Thus we aimed to propose a new filter to handle this impulsive noise to improve the QRS detection accuracy in wearable ECG measurement. Methods: ECG signals were acquired by the Lenovo Smart-vest, which is a 12-lead wearable ECG collection device, with a sample rate of 500 Hz. The consecutive ECG signals were manually visual-scanned to pick out the episodes including impulsive noises. A fixed time window of 10 s was used for segmenting the ECG episodes. Then, each 10-s ECG episode was processed by Butterworth band-pass filter (0.5–35 Hz). The common Pan & Tompkins (P&T) QRS detector was performed on the filtered signals. A flexible threshold of 60 ms was used to confirm the true positive detection for QRS complex. One hundred episodes with the detection accuracy less than 60% were selected as the test data for the new proposed impulsive noise rejection (INR) filter. The new INR filter was designed with the combination of first order difference, fast Fourier transformation (FFT) and adaptive filtering. Results: Before the INR filtering, the average QRS detection accuracy of the 100 challenging ECG episodes was only 50.62%. As contrast, with the help of the INR filter, P&T detector can achieve a high detection accuracy of 76.32%. Significance: Impulsive noise is a challenging noise existing in the wearable ECG signals. The new designed INR filter can efficiently reject the impulsive noise, and make benefit for the accurate QRS detection in the dynamic environment.

Xiangyu Zhang, Jianqing Li, Zhipeng Cai, Shengyi Ma, Jian Zhang, Chengyu Liu

Automatic Detection of P Wave in ECG During Ventricular Extrasystoles

This work introduces a new method for P wave detection in ECG signals during ventricular extrasystoles. The authors of previous works which deal with detection of P waves tested their algorithms mainly on physiological records (sinus rhythm) and they reached good results for these records. Testing of P wave detection algorithms using pathological records is usually not provided and if it is, the results are notably worse than in the case of physiological records. The automatic and reliable detection of atrial activity in pathological situations is still an unsolved problem. In this work, phasor transform in combination with classification algorithm is used for P wave detection. Phasor transform converts each ECG sample into a phasor which enhances changes in the ECG signal. The classification is based on extraction of morphological features which are derived from each QRS complex. The results of classification are used for demarcation of areas in which P waves are searched using phasor transform. The proposed algorithm was tested on signals no. 106, 119, 214 and 223 from MIT-BIH arrhythmia database, in which the ventricular extrasystoles are present. For validation whether the algorithm is functional also for signals with physiological rhythm, it was tested on the signals no. 100, 101, 103, 117, and 122. The accuracy of the P wave detection in signals with ventricular extrasystoles is Se = 98.94% and PP = 98.30% and in signals without pathology is Se = 98.47% and PP = 99.99%.

Lucie Maršánová, Andrea Němcová, Radovan Smíšek, Tomáš Goldmann, Martin Vítek, Lukáš Smital

An Ensemble Empirical Mode Decomposition Based Method for Fetal Phonocardiogram Enhancement

Nowadays, fetal monitoring standard relies mainly on the analysis of fetal heart rate. However, signals like fetal electrocadiogram (fECG) and fetal phonocardiogram (fPCG) can offer complementary diagnostic information derived from the waveform analysis. The limitations of using, in particular, fPCG are: the signal to noise ratio (SNR) is very low because the recorded signal is a mixture of acoustic components originating not only from the fetus heart but also from the mother (maternal heart sounds (MHS), maternal organ sounds (MOS)) and other sources (power line interference, reverbaration noise, sensor and background noise). Moreover, it is dependent on gestational age, fetal and maternal positions, the data acquisition location. From the noise components the MHS presents a high correlation in the frequency domain with the fetal heart sounds (FHS). Thus, separation of MHS from acoustic recordings is not straightforward. In addition the MHS is a narrowband non-stationary signal. Thus, in this paper is proposed a method for fPCG enhancement from the recorded acoustic mixture based on the Esemeble Empirical Mode Decomposition (EEMD). This approach allows to analyze heart sounds into Intrinsic Mode Functions (IMFs) and it is adaptive and data driven. The performance of the proposed method is evaluated on a database with simulated fPCG signals.

Dragos Daniel Taralunga, G. Mihaela Neagu (Ungureanu)

The Automatic Detection of Epileptic Seizures Based on EEG Signals Processing: Investigation of Different Features and Classification Algorithms

Automatic detection of epileptic seizures has been extensively studied and documented in literature. However, the topic continues to be of interest as reliable algorithms for general use are still being investigated. The challenge comes from the complex nature of the EEG signal and of the epileptic seizure, as both show patient specific characteristics. This makes highly performing algorithms developed on specific datasets difficult to translate to a more general use case. To provide more insights into the characteristics of seizure and non-seizure EEG segments, this paper proposes and investigates several features. Feature combinations are selected and fed per patient to both an Support-Vector Machine and Random Forest classifier. The performance of the trained models varied per patient, feature combination and training algorithm, with the highest accuracy reaching 94%.

Alexandra-Maria Tăuţan, Ioana Mândruţă, Ovidiu-Alexandru Băjenaru, Rodica Strungaru, Dragoş Ţarălungă, Bogdan Hurezeanu, G. Mihaela Neagu (Ungureanu)

Atrial Fibrillation Detection from Wrist Photoplethysmography Data Using Artificial Neural Networks

Atrial fibrillation (AF) can be detected by analysis of the rhythm of heartbeats. The development of photoplethysmography (PPG) technology has enabled comfortable and unobtrusive physiological monitoring of heart rate with a wrist-worn device. Therefore, it is important to examine the possibility of using PPG signal to detect AF episodes in real-world situations. The aim of this paper is to evaluate an AF detection method based on artificial neural networks (ANN) from PPG-derived beat-to-beat interval data used for primary screening or monitoring purposes. The proposed classifier is able to distinguish between AF and sinus rhythms (SR). In total 30 patients (15 with AF, 15 with SR, mean age 71.5 years) with multiple comorbidities were monitored during routine postoperative treatment. The monitoring included standard ECG and a wrist-worn PPG monitor with green and infrared light sources. The input features of the ANN are based on the information obtained from inter-beat interval (IBI) sequences of 30 consecutive PPG pulses. One of the main concerns about the PPG signals is their susceptibility to be corrupted by noise and artifacts mostly caused by subject movement. Therefore, in the proposed method the IBI reliability is automatically evaluated beforehand. The amount of uncertainty due to unreliable beats was 15.42%. The achieved sensitivity and specificity of AF detection for 30 beats sequences were $$ 99.20 \pm 1.3\% $$ and $$ 99.54 \pm 0.64\% $$, respectively. Based on these results, the ANN algorithm demonstrated excellent performance at recognizing AF from SR using wrist PPG data.

Zeinab Rezaei Yousefi, Jakub Parak, Adrian Tarniceriu, Jarkko Harju, Arvi Yli-Hankala, Ilkka Korhonen, Antti Vehkaoja

EEG Spectral Asymmetry Is Dependent on Education Level of Men

An objective indicator based on the asymmetry of electroencephalographic (EEG) signal spectrum has been shown promising for screening of population to discover occupational stress. However, the factors other than stress affect the EEG spectrum. The aim of the current study is to investigate the role of education level on EEG signals’ band relative powers. For this purpose, 18-channel resting eyes-closed EEG was recorded from 30 men having Bachelor or higher education (tertiary education) and 16 men declaring to have lower, upper or post-secondary education (secondary education). For those signals, relative theta, alpha, beta and gamma powers were calculated. The results indicated increase in relative gamma power for the subgroup of men having tertiary education compared to the subgroup of men having secondary education. No significant alterations were revealed in other relative band powers. Higher relative gamma power of men having higher level of education could be related to the higher cognitive load in their everyday life, as widespread gamma activation has been previously demonstrated during cognitive tasks. The results of the current study suggest that the level of education is one of the factors to be taken into account in EEG based evaluation of occupational stress or mental disorders.

Toomas Põld, Maie Bachmann, Laura Päeske, Kaia Kalev, Jaanus Lass, Hiie Hinrikus

Artificial Neural Network Applied like Qualifier of Symptoms in Patients with Parkinson’s Disease by Evaluating the Movement of Upper-Limbs Activities

The Movement Disorder Society (MDS-UPDRS) defines characteristics to qualify various symptoms of PD, the present works propose to apply an Artificial Neural Network ANN to qualify symptoms based upon movement of upper-limbs activities. In this way, a system based on Arduino and Android mobile app were developed, where accelerometers are used to acquire and store the acceleration data from upper-limbs while PD patients were doing three activities: rest sitting, eating and brushing teeth, meanwhile their symptoms were classified by doctor between 0 (normal) to 4 (most severe impairment). After that, store data were processed and estimation on Power Spectral Density (PSD) was done, then this information and doctor’s diagnosis were used into the ANN training to evaluate the symptoms in PD patients. For the ANN training was used back-propagation model and many ANN configurations, until get the best fit between inputs (processed data) and output (doctor’s diagnosis). The results showed that trained ANN can be used like qualifier with a high degree of accuracy over the 90%, for the tests performed. Moreover, even though MSD-UPDRS allows to get an accurate diagnosis, there is not objective, so ANN could be fixed to be completely objective, being a great advantage with manual evaluation.

J. P. Bermeo, M. Huerta, M. Bravo, A. Bermeo

Nonlinear Dimensionality Reduction and Feature Analysis for Artifact Component Identification in hdEEG Datasets

The time-domain independent component analysis (ICA) is commonly used technique for neural and noise signal separation in electroencephalographic (EEG) data. Nevertheless, the estimated independent sources have to be further classified by an expert using predefined or learned features. Automatic algorithms on market suffer from unsatisfactory sensitivity and specificity mostly due to large inter-subject variability of the human EEG. Generalization of each learning machine depends on whether some discriminative features exist in inter and intra individual component space. We employ nonlinear dimension reduction technique called t-Distributed Stochastic Neighbor Embedding (t-SNE) to fit the data and visualize them in estimated feature space. Our approach is unsupervised and completely data driven. We focus on regularities in a real-world hdEEG component set that could be learned by robust feature classifier, e.g. a deep network. Furthermore, we also investigate relations between found data structure and commonly used criteria known from the literature.

Vlastimil Koudelka, Jan Štrobl, Marek Piorecký, Martin Brunovský, Vladimír Krajča

Comparison of Spline Methods for 3D Brain Mapping

Brain mapping is a topographical method that is frequently used in human scalp electroencephalogram (EEG) for two-dimensional (2D) or three-dimensional (3D) visualisation of electrical potentials distributed across the surface of the brain. In human research, accepted standards for EEG recording and mapping exist, however to date, no such standards have yet been developed for use with laboratory rats. We have selected methods typically used for 3D brain mapping in humans and applied them to a brain model of the Wistar rat. Spherical and 3D splines were implemented as methods of the interpolation. The validation of 3D maps was created by using simulated signals of human and rat brain activity. The Root Mean Square error (RMS error) was calculated for the evaluation of interpolation methods. In conclusion, our results showed that the 3D spline interpolation yielded a better electrical potential map in both the human brain model and the rat brain model.

Václava Piorecká, Vladimír Krajča, Tomáš Páleníček

Simulation, Modification and Dimension Reduction of EEG Feature Space

An automate classification of EEG time segments is frequently used technique across many neuro-scientific fields. Generally, segment classification results in labeled EEG time segments (e.g. physiological brain activity, epileptic activity, muscle artifacts or electrode artifacts). However, currently used methods are usually tested on artificial surrogate data and more general validation approach is needed. Here, a generalized statistical model of commonly used discriminating features obtained from real EEG data is presented for the first time. Multivariate probability density functions (PDFs) of classes are fitted on more than twenty thousand of testing segments from human EEG. An unique testing set is designed using a recent non-linear dimension reduction technique. Parametric and non-parametric PDF estimators are applied and compared in sense of feature space model.

Marek Piorecký, Eva Černá, Václava Piorecká, Vladimír Krajča, Vlastimil Koudelka

Can Textile Electrode for ECG Apply to EMG Measurement?

Electromyograms (EMG) are used as not only evaluation of muscle strength and muscle fatigue in medical but also those in sports science and biomechanics fields. It needs the expert knowledge to set electrodes on a certain muscle position every day to monitor EMG for long terms. We assumed that this problem would be solved by textile electrodes. In our previous study, we revealed that the stretchable conductive elastomers enabled to measure precise electrocardiogram (ECG) waveform compared with conventional Ag/AgCl electrodes (Okuno et al, Proceedings of international conference on healthcare, pp 42–43, 2014 [1]). However, EMG measurement has not been evaluated so far. Because EMG has a wider frequency band than the ECG, we need to be clear the electrode’s characteristics for EMG measurement use. The purpose of this research is to clarify whether the developed electrode can adapt to the EMG measurement. Healthy eleven adults were participated in our experiment as subjects (Age: 21.4 ± 0.8: mean ± S.D.). EMG was recoded from the tibial anterior muscle. EMG signal were collected by self-making myoelectric amplifier. The frequency band of the EMG amplifier was 30–500 Hz and sampled at 1 kHz. EMG was measured isometric contraction motion of the load 0, 1.25, 2.5, 3.75 and 5 kg. As the results, the correlation coefficients between the load and the RMS of the developed electrode and the Ag/AgCl electrode were r = 0.918 and r = 0.912, respectively. This result showed that the development electrode can be used for muscle strength evaluation.

Daisuke Goto, Naruhiro Shiozawa

Automatic Detection of Strict Left Bundle Branch Block

Strict (true) left bundle branch block (tLBBB) ECG morphology is a new diagnostic marker in cardiology that was proposed to predict cardiac resynchronization therapy (CRT) responders. In this paper we present an algorithm for the automatic detection of tLBBB. This algorithm includes mid-QRS notching and slurring detection, QRS duration measurement and tLBBB morphology detection. All required morphologies are detected in the time domain using thresholding of simple features of signal. In order to test our algorithms, three experts labelled 78 ECG records (12 leads, fs = 5 kHz, 15 min); 51 records were labeled as tLBBB. The proposed algorithms were tested showing overall sensitivity and specificity 98 and 86%, respectively, in cases where all three experts reached full consensus (82% of the dataset). Our method showed lower sensitivity and higher specificity 96% and 88%, respectively, for the dataset including cases where experts mutually disagreed, consensus has been reached through expert discussion in these records.

Radovan Smisek, Pavel Jurak, Ivo Viscor, Josef Halamek, Filip Plesinger, Magdalena Matejkova, Pavel Leinveber, Jana Kolarova

Classification of Children with SLI Through Their Speech Utterances

Many young children have speech disorders. The research focused on one such disorder, known as specific language impairment (SLI) or developmental dysphasia in Czech (DD). A major problem in treating this disorder is the fact that specific language impairment is detected in children at a relatively late age. For successful speech therapy, early diagnosis is critical. This paper provides the issue of identifying SLI in children on the basis of their speech and presents two different approaches to this issue using. The First access is a new method for detecting specific language impairment based on the number of pronunciation errors in utterances. The success rate of detection of children with SLI is higher than 93%. An advantage of this method is its simplicity in the form of a simple test. This test is used in a mobile application SLIt Tool which is designed for iPad. The second method is based on the acoustic features of the speech signal. The feature set used to analyze speech data contains 1582 acoustic features and the success rate is almost 97%. An advantages of these different methods is that they could be used together to develop of the robustness automatic detection system.

Pavel Grill

Research on Respiratory Signal Based on Angular Velocity

Precise monitoring of human respiration is crucial to the diagnosis of a wide range of respiratory and cardiovascular disorders and (thus) is of great interest to both clinicians and researchers. Existing measurements may include electrocardiography (ECG), nasal cannula and respiratory plethysmography. However, low comfort levels and signal shifts which are often observed in these techniques pose limitations for long-term, accurate monitoring of human respiration. In this paper, we develop a convenient respiratory signal acquisition method based on angular velocity derived from suprasternal notch. Research has found that waveforms collected from the suprasternal notch display higher robustness, as well as less gender variability. We use the median filter method and intersection detection technique to extract the respiratory waveform, respiratory frequency and respiratory phase parameters. And validated the respiratory signals derived from suprasternal angular velocity in both males and females. The extracted parameters are validated against a carbon dioxide concentration acquisition device, which serves as our golden reference platform. The results demonstrate the potential of suprasternal-derived angular velocity as a simple, low-cost and unobtrusive method for monitoring human respiration.

Guo Dan, Junhao Zhao, Huanyu Yang, Xiaohong Weng, Zhemin Zhu

Comparison of Brain Computer Interface for Selecting Menus that Utilize EEG and NIRS

The authors attempted to develop an environment control system for severely handicapped bed-ridden patients. In this study, we used electroencephalograms (EEG) and near infrared stereoscopy (NIRS) to test and compare a system called “brain computer interface” for the purpose of selecting menus. The feature of the EEG-based system is that wavelet analysis is used to detect the event-related potential P300, and then, to determine the selected menu. Additionally, an appropriate stimulus-to-stimulus interval time of the menu was derived to be approximately 0.50–0.75 s. Regarding the NIRS-based system, real-time feedback was effective in increasing oxygenated hemoglobin (Oxy-Hb) signal, which resulted in a higher success ratio. The average success ratio of EEG-based system was higher than that of NIRS-based system. In general, using the proposed system, the time required to select a menu is shortened, and the feeling of restraint is reduced.

Akihiko Hanafusa, Keiyo Arai, Yukari Okawa

Preprocessing of the BSPM Signals with Untraditionally Strong Baseline Wandering

The BSPM is a special setup of the ECG measurement with many of electrodes (20–256) on the body surface. Results of the measurement are strongly dependent on many conditions like body shape, contact of electrodes and skin, patient position and movements. Of course, these conditions are crucial also for standard ECG measurement, but obviously, problems with the conditions are more probable during the BSPM signals acquisition. In this paper, we would like to present a problem with the Body Surface Potential Mapping (BSPM) ECG preprocessing caused by unexpected signal interruption due to the significant baseline wandering and derivate problems which are generated by solving of this baseline wandering filtration. This problem is major for next signal processing (mainly ECG delineation) because the baseline wandering problem is closely connected with the determination of ECG signals’ isoline. We use a system of 120 electrodes on body front and back. The experimental measurements are arranged in the clinical environment with maximal treatment to electrodes position and contact of electrodes and skin at the beginning of the measurement. Unfortunately, obtained signals contain often extreme baseline wandering bedsides of standard artefacts. This baseline wandering seems to be created most likely by patient movements and a change of the electrodes contact. Moreover, we have observed that the standard artefact filtration and the extreme baseline wandering filtration are against each other.

Michal Huptych, Matěj Hrachovina, Lenka Lhotská

Empirical Mode Decomposition in Analysis of Hemodynamic Response to Static Handgrip

The empirical mode decomposition (EMD) of biological signals is used to detect reaction to physiological stimuli and to identify global trends in slowly changing variables. We applied EMD to analyze hemodynamic reaction to handgrip in 9 healthy males (aged 21.3 ± 0.3 years) and 10 male patients following coronary artery bypass grafting (aged 55 ± 6 years). Subjects squeezed a dynamometer with 30% of individually determined maximal force for 3 min. The aim of the study was to check whether the application of EMD to the signals could bring any objective quantitative or qualitative measures allowing one to distinguish physiological states of healthy subjects and patients. Hemodynamic data were collected using a battery-powered, ambulatory impedance cardiography device (ReoMonitor) incorporating a single ECG channel. Heart rate (HR), R-R interval (RR), stroke volume (SV), cardiac output (CO), left ventricular ejection time (ET), pre-ejection period (PEP), maximum amplitude of the dz/dt signal (Amp), and basic chest impedance (Z0) were calculated automatically using the software earlier developed for ReoMonitor. The dedicated computer program allows to calculate and display the dynamics of basic and derivative parameters, describing the impact of systolic time intervals on RR intervals, or the relationship between them (e.g. PEP/ET). The EMD procedure was applied to identify the components of each basic hemodynamic parameter and all their derivatives. We observed the most pronounced effect of handgrip in second and third intrinsic mode functions (IMF), which particularly manifested in parameters describing the ratio of systolic time intervals to the length of RR.

Norbert Olenderek, Gerard Cybulski, Krzysztof Krzemiński, Wiktor Niewiadomski, Anna Gąsiorowska, Anna Strasz

A Rapid Assessment Method on Fistula Stenosis Staging for Hemodialysis Patients

The AV access is usually evaluated by feeling thrill and pulsation through palpation, listening for the bruit by using a stethoscope, Doppler ultrasound imaging, or angiography, etc. However, these techniques require specific equipment and operator. Phonoangiography is a noninvasive tool for identifying vascular diameter change. In this study, a mock model has been set up to simplify the simulation of blood flow condition. Phonographic signal is recorded by electronic stethoscope and further signal processed. The relationship of phonographic signals and stenotic lesions is studied. Early detection of hemodialysis access problems such as stenosis and thrombosis is very important issue. The purpose of this study is to develop a phonographic system to evaluate arteriovenous shunt (AVS) stenosis of hemodialysis patients. The degree of stenosis (DOS) is used as an index to classify the AV access condition, and is determined by the narrowing percentage of normal vessels. In this mock model, the DOS is set to be varied from 0, 50, 70, 80, 85, 90, 92.5 to 95%. The empirical mode decomposition (EMD) method is applied to analyze the relationship between DOS and spectrogram. Verification is based on Doppler ultrasound which is the golden standard in clinical application. From the experimental results, the proposed method is demonstrated to be feasible for charactering the staging of DOS conditions. There is a great correlation between the phonoangiography and the severity of DOS in AV access. This noninvasive method may be useful and potential for early detection in home-care use.

Yu-Yao Wang, Chung-Dann Kan, Wei-Ling Chen, Kuo-Sheng Cheng

Accuracy Comparison of ML-Based Fall Detection Algorithms Using Two Different Acceleration Derived Feature Vectors

Falls among the elderly are an important health issue which can lead to serious consequences. Unintentional falls in the elderly are the most common cause of nonfatal injuries. Different algorithms have been proposed for fall detection using vision based, ambient or inertial sensors. In this experiment, we used data collected from 16 subjects performing 15 tasks: 12 activities of daily living and 3 simulated falls. Subjects were equipped with a waist-mounted IMU to collect tri-axial accelerometer data during the activities. We derived features from accelerometer data on time-windowed identified activities and divided them into 2 different feature vectors (FV) that are used for fall detection algorithm. The selection was made based on the computational complexity of the features. We used different machine learning (ML) techniques to distinguish fall events from non-fall events (i.e. activities of daily living). In this paper, we compared and analyzed the accuracy of fall detection for different ML-based algorithms using the two accelerations-derived feature vectors for potential real-time implementation. The accuracy of the selected models ranged from 80.1 to 90.0% for FV1 and from 87.2 to 98.6% for FV2. The support vector machines algorithm achieved the best performance with accuracy 98.6%, sensitivity 98.7% and specificity 98.6% for FV2.

Sara Zulj, Goran Seketa, Igor Lackovic, Ratko Magjarevic

The Value of New Atomic Sensors in Medical Diagnostic Procedures

The new generation of atomic magnetic sensors with sensitivity of 10 pT/rtHz provides new tool for assessment of biological magnetic signals such as MCG, MEG or other neurological signals. The atomic sensors with such high sensitivity always require attenuation of the spurious magnetic signals with shielding of the sensor and the subject. Additionally the best sensitivity of sensors is achieved in the total magnetic earth field close to zero. Authors have designed, based on a Vacuumschmelze room, the laboratory for the atomic sensors measurements with the compensation coils system zeroing out the magnetic field of the earth within whole area inside the shielded volume. The preliminary measurements have proven that diagnostic signal of MCG can be monitored by two parallel sensors. The results confirmed the ability of the multisensors examination of the distribution of the magnetic field magnitude on the surfaces of chest, scalp or other fragments of human body. In most practical situations the vector of the magnetic field is perpendicular to the surface of tissue generating it and the field maximum is exactly over the area of interest e.g. where the neurons are placed. Therefore the maps measured by the atomic sensor arrays can be more precise than isopotential maps where the magnetic field gradient parallel to the surface is detected. We could also expect that the measured magnetic field will have high amplitude because of the smaller dimensions of sensors and low attenuation of the magnetic field by bones.

Kazimierz Peczalski, Tadeusz Palko

Assessment of Micro T-Wave Alternans Using T-Wave Morphology-Based Methods

Microvolt T-wave alternans (MTWA) is a risk marker for life threatening arrhythmias, defined as beat-by-beat alternation of the T-wave amplitudes. Sensitive to noise, MTWA classical method (CM) requires accurate determination of T-wave peaks. This study assessed alternative methods prescinding this limitation. Fifty ECG recordings from PhysioNet T-Wave Alternans Database were assessed (channels 1 and 2). A sequence of 128 sinus beats was extracted from each signal. The FFT of the 128 T-wave peak value series was employed to perform CM, taken as reference. Further, T-waves were isolated and consecutively concatenated, composing an artificial continuous (AC) signal. Over AC two methods were investigated: (i) Hilbert Transform approach (HT)—assessed by the FFT of the AC envelope, calculated by HT; (ii) Short-time spectral approach (STS)—assessed in the average of 96 FFT obtained from moving windows with 32 consecutive T-waves, displaced one by one. MTWA was calculated as ‘alternans ratio’, (alternans peak divided by the SD of 10 vicinal harmonics). CM versus HT and CM versus STS were compared by correlation coefficient, Bland-Altman charts and ROC. Correlation coefficient were, respectively, channel 1: 0.787 and 0.797 and channel 2: 0.835 and 0.836 (p < 0.001 for all). Bland-Altman plots showed nonsignificant (NS) differences for both channels. The area under ROC curves of CM, HT and STS were, respectively, 0.75, 0.80 and 0.71 (channel 1) and 0.77, 0.80 and 0.70 (channel 2) (p = NS for all). As a conclusion, quantification of MTWA based on T-wave morphology analysis is feasible, accurate and reproducible, and have potential clinical application.

Thaís Winkert, Paulo Roberto Benchimol-Barbosa, Jurandir Nadal

Electrode Optimization for Bioimpedance Based Central Aortic Blood Pressure Estimation

Evidence suggests that assessment of the central aortic pressure (CAP) of blood is vital for accurate detection of cardiovascular events and for making treatment decisions. Direct CAP measurement is possible and is used in clinical environment, however it is both costly and carries increased risk, therefore it is not suitable for preliminary screening and monitoring. Indirect noninvasive assessment of CAP has been around for several years. Applanation tonometry which is largely based on the research by O’Rourke et al. is method of choice and sometimes even described as gold standard for the noninvasive assessment of the central pressures, the pulse wave velocity and the heart rate variability. Pressure sensor is typically placed on the radial artery, and central aortic pressure is estimated by generalized mathematical transformation of the recorded waveform. While widely used the method has serious drawback—strong dependence on operator skills. The electrical bioimpedance (EBI) has emerged as viable alternative in search for the measurement methods with better repeatability. Its applicability has been confirmed in several studies involving simultaneous invasive CAP measurement, and comparative measurements with AtCor Medical SphygmoCor device. Further refinement of the method is considered in proposed paper. Electrical attachment of the bioimpedance measurement unit to the body is investigated and discussed.

Margus Metshein, Hip Kõiv, Paul Annus, Mart Min

Photoplethysmographic Measurements on Clinical Patients (>65 y) and Healthy Cohorts Between Ages of 18–75 y

The biomedical information on different indexes like arterial elasticity index (AEI), arterial age (AA) is used in many cases. However, they applicability for diseases earlier prediction like arteriosclerosis (AS) is seldom applied. Many illnesses are becoming common, especially cardiovascular disorders (CVD) among elderly people, and in females. It is predicted that the negative impacts of AS on young people can be greater than on the elderly people in the long run because of sedentary lifestyle. Degenerative changes in the arteries have many causes in addition to the lifestyle. Arterial elasticity (AE) would provide a direct indicator for cardiovascular healthiness and predict AS. AE can be challenging in the cases of elderly, but also in the case of the young persons whose endothelial functions have been earlier very good. The vessel properties would be important to know for characterization of both arterial diseases and the development of reliable devices. Photoplethysmography (PPG), and especially its response pulse wave decomposition, envelope analysis, and its second order derivative (SDPPG) open the new health information for clinics. PPG signals are correlated with the alterations in blood pressure, blood flow, arterial elasticity, and health indexes. Exposure of human to physical exercise has been shown to improve endothelial function in patients with risk factors and heart failure. Exercise has been shown to be protective to cardiovascular disease. In addition according to this study, the exact mathematical solution for the pulse wave analysis has be replaced by numerical analysis method. In addition, a probability density function and a coherence function suits well to the inherent resting PPG process, and giving some intrinsic properties of the arterial pulsation phenomena.

Matti Huotari, Juha Röning, Kari Määttä, Pekka Romsi

Round Cosine Transform Based Feature Extraction of Motor Imagery EEG Signals

Brain Computer Interfaces (BCIs) are systems with great potential for the rehabilitation of people with severe motor injuries. By analyzing a subject’s brain waves, it is possible to detect patterns and translate his “thinking” into device commands, like prosthesis or a robotic arm. This research presents an EEG processing method, which is capable of detecting patterns of the subject’s motor imagery, splitting the patters in left or right hand imagery. The proposed method considers the Round Cosine Transform (RCT), a low computational complexity transform, and an artificial neural network (ANN) module which identifies the patterns. The method has been tested in a real-time (RT) continuous EEG processing experiment simulation, controlling a mouse arrow horizontally on a screen based on the subject’s imagery motor activity. The performance of the proposed method is evaluated in terms of the mutual information (MI), classification time and misclassification rate (%). The achieved results were 0.49 bits, 5.25 s and 15.6%, respectively.

R. B. Braga, C. D. Lopes, T. Becker

Combined Phase and Magnitude Metric for Validation of Lower Limb Multibody Dynamics Muscle Action with sEMG

This study presents and applies combined phase and magnitude metrics for validation of multibody dynamics (MBD) estimated muscle actions with simultaneous registered sEMG of lower limb muscles. Subject-specific tests were performed for acquisition of ground reaction forces and kinematic data from joint reflective markers during NG, SKG and SR. Inverse kinematics and dynamics was performed using AnyBody musculoskeletal personalized modeling and simulation. MBD estimated muscle activity (MA) of soleus medialis (SM) and tibialis anterior (TA) were compared on phase, magnitude and combined metric with simultaneous acquisition of sEMG for the same muscles. Results from quantitative metrics presented better agreement between MDB MA and sEMG on phase (P) than on magnitude (M) with combined (C) metric following the same pattern as the magnitude. Soleus medialis presented for specific subject lower P and M error on NG and SKG than at SR with similar P errors for tibialis anterior and higher error on M for TA at NG and SKG than SR. Separately and combined quantitative metrics of phase and magnitude presents as a suitable tool for comparing measured sEMG and MBD estimated muscle activities, contributing to overcome qualitative and subjective comparisons, need for intensive observer supervision, low reproducibility and time consuming.

Carlos Rodrigues, Miguel Correia, João Abrantes, Jurandir Nadal, Marco Benedetti

Detection of Sleep Stages in Temporal Profiles in Neonatal EEG—k-NN versus k-Means Approach: A Feasibility Study

The aim of this feasibility study is to experimentally verify the detection of changes of sleep stages in neonates with our proposed semi-automated approach using k-NN classification in comparison with a fully automated approach using simple k-means cluster analysis for classification (instead of k-NN). Our semi-automatic approach uses the k-NN classifier trained on etalons (prototypes) created by semi-automated etalons extraction (k-means for etalons suggestion and expert-in-the-loop for verification). Both methods are compared to labelling of sleep stages made by an experienced physician Dr. K. Paul. An EEG recording of full-term neonate is chosen from group of EEG recordings: full-term and preterm neonates recorded from eight electrodes positioned in standard conditions. The EEG recording is digitally preprocessed by mean-removal filter (no other filters are applied) and segmented adaptively. For each segment, 24 features are extracted and send to two classification processes: k-means and k-NN. Classified segments are plotted in temporal profiles (class membership in time) that are analysed for sleep stages using our method of creating a single detection curve from all channels and a threshold is applied on this detection curve to detect sleep stages.

Vladimir Krajca, Hana Schaabova, Vaclava Piorecka, Marek Piorecky, Jan Strobl, Lenka Lhotska, Vaclav Gerla, Karel Paul

Muscle Synergies for Motor Control Evaluation

Muscle synergies have been proposed to be a modular organization for muscle coordination that map high-level task goals, or motor intentions, into motor actions. Muscle synergies and other types of modular organization have been used to explain muscle coordination during a variety of motor behaviors in many different species. In some instances, new synergies may emerge when a new motor task is presented and the recruitment of the synergies may be altered. Here, we used a database to investigate muscle activity of the right hand during seven distinct limb motions in order to extract muscle synergies: hand open, hand close, supination, pronation, wrist flexion, wrist extension, and rest. Database content EMG signals collected from seven sites on the forearm and one site on the bicep, with an electrode placed on the wrist to provide a common ground reference. Classification scheme is based on the synergies between a functional group of muscles. The muscular synergy is evaluated using different techniques like the normalized power spectral densities (PSD), the cross-correlation matrix of muscular force (estimated through the root mean square (RMS) value of EMG amplitude) and the intermuscular coherence between different sets of muscles. We investigate the relationship between muscle synergy recruitment and functional motor outputs and hypothesized that a common pool of muscle synergies producing consistent task-level biomechanical functions is used to generate different motor behaviors.

Fernando J. Muñoz Z., Natalia M. López C., Flavio Roberti, Max E. Valentinuzzi

Methodology for Quantification of Frontal Muscle Electromyography Contamination in the Electroencephalogram

The electroencephalogram (EEG) is the record of cerebral electrophysiological activity along the scalp in which it has been widely used in several applications, for example, the quantification of the cognitive capacity focusing on the diagnosis or even Brain Machine Interfaces (BCI). However, neural data are frequently contaminated by artifacts that may originate from recording devices or by non-brain physiological activities, such as the blink and the contraction of the scalp muscles. This last represents a considerable challenge in the removal of EEG artifacts due to high amplitude and broad frequency range, which makes it difficult to remove by conventional filtering. Thus, some applications such as BCI systems may occasionally be associated with frequent contractions of head muscles corrupting the EEG control signal. This requires the application of a number of filtering techniques. However, the standard gold techniques still contain limitations, such as not completely eliminating noise in all EEG channels. For this reason, besides to the study of the techniques is helpful to understand the electromyography (EMG) contamination along the scalp. The present work aims to quantitatively estimate EMG noise in 16 bipolar channels of EEG distributed along the scalp according to the 10–20 system. This estimation was based on experimental protocol considering the simultaneous acquisition of EEG and EMG of the frontal muscle sampled at 5 kHz. The protocol consisted of 15 beeps, while listening to these beeps the volunteer made a contraction of the frontal muscle. The mean power of the EEG contaminated by EMG of frontal muscle contraction was compare between the periods of muscle contraction and non-contraction. The results show a mean increase of approximately 74.9% in the power of EEG signals during the muscular contraction. Thus, we conclude that frontal muscular contamination is present on the all EEG rhythms and all over the scalp.

Gustavo Moreira da Silva, Fabio Henrique Monteiro Oliveira, Luciano Brink Peres, Carlos Magno Medeiros Queiroz, Luiza Maire David Luiz, Samila Carolina Costa, Marcus Fraga Vieira, Adriano O. Andrade

Effects of Nitroglycerin to Ballistocardiography by EMFi

The purpose of this work was to study the effect of nitroglycerin (glyceryl trinitrate) to ballistocardiographic signal (BCG) recorded in sitting position by using Electromechanical Film (EMFi) sensors. ECG, BCG, ankle pulse signal and carotid pulse (CP) signal from the neck near the carotid artery were recorded from a single person and duration of the signal components according to R wave of the ECG and amplitudes of the signals were studied. In the first study the effect of 1 nitroglycerin pill was studied and in the second study the effect of exercise and the intake of 2 nitroglycerin pills were examined. The time domain properties of BCG, CP and ankle pulse signals stayed somewhat stable due to nitroglycerin intake. Noticeable increase was seen in some systolic signal amplitudes. Diastolic signal amplitudes mainly decreased. Signal traces became smoother and the fluctuation of the ballistic signals decreased. Nitroglycerin intake had a major but temporary effect on the heart-vasculature system due to increased aortic elasticity.

Jarmo Alametsä, Jari Viik

The Evaluation of the Tremor: Signal Database of Healthy Control Subjects

A tremor an involuntary rhythmic oscillatory movement of a part of the body—belongs to one of the most disabling features of multiple sclerosis (MS). In clinical practice, the tremor is currently classified according to clinical scales. Unfortunately, this approach is fully subjective in principle, and the objective classification is still missing. As is shown in the literature, the tremor can be investigated by accelerometers and gyroscopes based on the frequency analysis and other advanced methods of signal processing. A condition of the successful development of these methods is an existence of a signal database of healthy subjects. This paper concerns with the collecting of the signal database of healthy control subjects. The signals were acquired on the group of healthy subjects aged from 18 to 50 years (20 subjects). For each patient, one-minute records of postural tremor (for both right and left hand, with and without closed eyes; 4 records together) have been acquired, and also several clinical tests have been passed (a measurement of a strength by a handgrip, a pinch key, and a trippod test, a nine-hole peg test, a coin rotation task test, and a tip pinch test). All records have been supplemented by anamnestic data.

Jan Havlík, Patrik Horák, Kamila Řasová, Jitka Řezníčková, Josef Zeman

Biomechanics, Rehabilitation and Prosthetics

Frontmatter

Design and Manufacture a Haptic System to Rehabilitate the Muscles of the Hand

The paper’s objective is to fabricate a novel haptic system for hand muscular rehabilitation applications after hemiplegia that happens after stroke. This prototype is categorised as end-effectors. By using this equipment, patient can perform both active range of motion and passive range of motion. Each rehabilitation device equipped haptic technology for evaluation of force exerted by patient’s limb using multi-axial force sensors. Unlike previous proposed devices and state of the art devices, our proposed device evaluates force exerted only receiving feedback of haptic device the current draw of DC motor. In fact, no force sensor has been used in our proposed haptic device.

Mina Zareei, Ali Zamani, Ali Tavakoli Golpaygani, Mohammad J. Sadeghi

Are Micro Back Markers on Thin Film of Scaffold Effective to Evaluate Contractive Movement of Myotube?

The scaffold of the transparent film with micro markers has been designed to evaluate the contractive movement of myotube under the electric pulse stimulations in vitro. The scaffold of a thin film (6 μm of thickness) of polydimethylsiloxane was made with ten million micro markers: 4 μm of diameter, 2 μm of height, and 30 μm of interval. Ten million markers were made on the backside of the scaffold by the photolithography technique. C2C12 (mouse myoblast cell line) was seeded on the film at the counter surface to the markers at the density of 5000 cells/cm2. The cells were cultured for 12 days in the medium containing 10% fetal bovine serum and 1% penicillin/streptomycin at 310 K with 5% of CO2 content. The electric pulses (1 s of pulse cycle, 1 ms of pulse width) were applied between platinum electrodes dipped in the medium. The myoblasts were able to be cultured on the film to be differentiated into myotubes. The thin film with micro markers was successfully made of polydimethylsiloxane, and had enough transparency for observation of myotubes by the microscope. The myotube was contracted synchronously with the stimulation of electric pulses. The contractile movement was able to be analyzed by the repetitive displacement of the length between backside micro markers of the film. The micro backside markers on thin film of scaffold are effective to evaluate contractive movement of the myotube.

Yusuke Takahashi, Shigehiro Hashimoto, Haruka Hino

Study on Walking Training System for Using High-Performance Shoes with Human Compatibility

The number of elderly in the Japanese population has been increasing, and is expected to reach about 40% by 2060. This means that those aged 65 and over in Japan will be roughly every one in 2.5 persons (Cabinet office, Government of Japan, Director General for Policies on Cohesive Society, “H.26 Aged Society White Paper”, 2014, [1]). With this are increases in the need for elder-to-elder nursing and shortage in and an increased burden on care takers. These developments have resulted in efforts to promote independence among the elderly—something that has brought walking to the attention of those promoting good health and independence among the elderly. The increasing number of accidental falls among the elderly while walking (Ministry of Health, Labour and Welfare, “Comprehensive Survey of Living Conditions” IV conditions of care, [2]). Among the main factors in falls are a deteriorating center of gravity of balance due to declining physical performance and weakening in the muscular strength of the lower limbs. In this study, we focused on shoes to be worn daily in walking aimed at both assisting walking and preventing falls. Further, we proposed training in walking that is continues and daily that detects and corrects the center of balance during walking. To add detection of staggering, we used a sponge-core soft-rubber actuator consisting of open-cell foam sponge coated in silicon rubber. This actuator changes stiffness with inner pressure. Equipping insoles, with it means that it can be used for both detecting the pressure distribution of the foot sole while prompting correct walking by changing the stiffness of the insole. We also developed a means of walking status presentation that confirms walking status on a display in real time.

Yasuhiro Hayakawa

Ergonomic Assessment of an Active Orthosis for the Rehabilitation of Flexion and Extension of Wrist

Muscular stiffness and limb rigidity are two main consequences of Parkinson’s disease. These motor symptoms may be present in distinct parts of the body, influencing functional tasks executed by hands. To aid people suffering from these motor symptoms, we developed an active wrist orthosis whose purpose is to enable increase the flexion and extension range of motion of the wrist joint. We identified five relevant ergonomic variables that should be considered when using the orthosis in the clinical practice: (i) device stability, (ii) forearm position; (iii) muscular strength; (iv) amplitude of motion; and (v) mass of the device. These variables were identified based on the observation of movements while users executed the flexion and extension of the wrist with and without the device. In this research, we present a description of the developed orthosis and an evaluation of the ergonomic variables (i), (ii) and (iii). An enhanced support structure has been used with the orthosis and shown to lead to a stability improvement. Electromyographic analysis showed that the use of the orthosis does not introduce undue muscular load on the user at distinct angular positions of the forearm.

Adriano O. Andrade, Julien Bourget, Samila Costa, Adriano Pereira, Michael I. Okereke, Marcus Fraga Vieira

Muscle Stiffness Estimation Using Center of Pressure Fluctuations Induced by Electrical Stimulation

We proposed a novel technique to estimate muscle stiffness using center of pressure (COP) fluctuations induced by electrical stimulation. Six participants stood on a force plate and the COP displacement was measured with and without electrical stimulation applied to the gastrocnemius muscle. The displacement measured in the stimulated condition involved both intrinsic and electrically induced fluctuations. To obtain the intrinsic fluctuation, the measured displacement was smoothed using a Kalman filter constructed by approximating the displacement measured in the non-stimulated condition with an autoregressive model. The intrinsic fluctuation was subtracted from the measured displacement to obtain the electrically induced fluctuation. The fourth-order transfer function from the electrical stimulation to induced fluctuation was identified using a singular value decomposition method. The transfer function had natural frequencies of approximately 2 and 0.3 Hz. The former was close to the natural frequency of the gastrocnemius muscle, and the latter was close to the resonance frequency around the ankle joint. The proposed method can provide muscle and ankle joint stiffness in a standing posture.

Takanori Uchiyama, Ayana Sugiyama

Gait Ratios and Variability Indices to Quantify the Effect of Using Smartphones in Dual-Task Walking

Smartphone use is one of the most common activities performed while walking: recent studies showed how this behaviour affected spatio-temporal, smoothness, symmetry and regularity gait parameters. In this study, we investigated a subset of additional gait parameters, potentially indicative of gait instability, to check whether concurrent smartphone activities cause deviations from stable walking. Ten young healthy adults were asked to walk outdoor normally and while performing five smartphone-based dual-task activities, with different levels of cognitive effort. Three groups of gait parameters, extracted by a single waist-mounted tri-axial inertial sensor, were analyzed: Gait Ratios group included Stride-to-Stance Time Ratio (SSTR)—equal to the golden ratio $$ \upvarphi $$  ≈ 1.618 in normal walking—and Walk Ratio (WR)—the ratio between Step Length (SL) and cadence, roughly constant within healthy subjects—Variability Measures group included Coefficients of Variation (CV) of SL and step time; Acceleration Ratios group composed of Root Mean Squared acceleration Ratios (RMSR)—the ratio between rms along a single direction and the total rms acceleration. When a dual-task is present, SSTR did not show significant variations from Baseline. A continuous typing activity with low cognitive engagement caused a significant decrease of WR with respect to all the other tasks. RMSR in the mediolateral direction and the CV SL showed visible yet not significant proportion with the amount of experienced cognitive effort. The resulting alterations were in general inconclusive as to their possible link with a reduced ability to adapt the locomotion structure to the context changes, even if for some parameters the observed proportion with cognitive effort and visual domain may need to be deepened on a bigger sample size, possibly including more challenging dual-task demands.

Carlotta Caramia, Ivan Bernabucci, Carmen D’Anna, Cristiano De Marchis, Maurizio Schmid

Split-Belt Treadmill to Study Reactive Responses to Unexpected Gait Perturbation

The aim is to presents a solution and realization of the design of new split-belt treadmill for controlled, unexpected perturbation during walking to study recovery responses and dynamic stability of the human gait. The construction of the split-belt treadmill consists of several subsystems. The most important subsystems are: actuator, control and sensory subsystem. Actuator subsystem is based on two asynchronous motors, two inverters and two gears (for each belt separately). Control subsystem is made up of Modbus communications between the control computer and two inverters with respect to the parameters of the asynchronous motors. The sensory subsystem is based on the incremental angular speed sensor used to record the behavior of the treadmill belts. The control itself is created through the MatLab software and special custom-made user interface that allows to define a wide range of perturbation schemes. It was then verified whether the belts had the desired speed. Verification of the system has shown that at the recommended speeds of running the belts (at 2.4 km/h), the system is stable, shows no variations in proband load, and real changes in belt velocities are achieved with minimum deviations from the desired values. The main benefit of the described work is the creation of a functional control of the prototype of the treadmill for controlled, mechanical gait perturbations. The split-belt treadmill is designed to study reactive responses during walking that can be further used to fall-risk assessment, clinical or rehabilitation intervention.

Slavka Viteckova, Patrik Kutilek, Veronika Kotolova, Radim Krupicka, Zoltan Szabo, Jan Kauler, Jan Hybl

Measurement of Mechanical Properties of Enamel Based on Resonant Ultrasound Spectroscopy

Mechanical properties is critical for developing dental materials and designing dental prosthesis. The aim of this study is to investigate the mechanical properties of human enamel material based on resonant ultrasound spectroscopy method (RUS). First, some pure enamel specimens were prepared carefully from five fresh human teeth. Under the assumption of transverse isotropic biomaterial, for all enamel specimens, the theoretical resonant frequencies were calculated using Rayleigh-Ritz method, the experimental resonant frequencies were extracted from resonant ultrasound spectroscopy, and then the optimal elastic constants was estimated based on based on the experimental and theoretical resonant frequencies using Levenberg-Marquardt method. In addition, the mechanical parameters, including Young’s moduli, Shear moduli, and Poisson’s ratios, were also calculated based on the optimal elastic constants. The result showed that RUS method exhibited more consistency of mechanical parameters than previous studies. This method may provide more precise measurement of mechanical properties of Enamel materials.

Haijun Niu, Fan Fan, Rui Wang, Qiang Zhang, Pengling Ren

Evaluating the Effect of Changes in Bone Geometry on the Trans-femoral Socket-Residual Limb Interface Using Finite Element Analysis

A prosthetic socket used by a lower limb amputee should accommodate the patient’s geometry and biomechanical needs. The creation of a geometrically accurate subject-specific finite element model can be used to provide a better understanding of the load transfer between socket and limb. There has been a limited number of finite element studies of trans-femoral sockets with all current models only including the femur and ignoring the pelvis. This study looked to evaluate the effect that including the pelvic bone as well as the femur in a finite element model has on the contact interface between the prosthetic socket and residual limb. This was done by creating a finite element model from a computerised tomography scan of a trans-femoral amputee. This model included three-dimensional geometry, nonlinear material properties and frictional contact between the residual limb and prosthetic socket. It was found that without the pelvic bone the contact pressures peaked at the distal end region of the residual limb (peak of 95 kPa). However by including the pelvic bone the contact pressures were instead concentrated at the ischial loading region (peak of 364 kPa). The shear stresses experienced on the socket-residual limb interface were also simulated. The results obtained in this study can be used to provide more of an understanding of the loading on the residual limb for the design and creation of future trans-femoral sockets.

Alex van Heesewijk, Andy Crocombe, Serge Cirovic, Mathew Taylor, Wei Xu

Monitor Aided Radio Control Mobile Robot (MARCMR)

The term robot comes from the Czech word robota, which when translated means “forced labor”. Generally, all the robots in the world are designed for monotonous tasks. The robots handle the jobs that are difficult, dangerous or boring for a human to perform. In the medical world robots have now taken over many tasks; from a basic robotic helping hand to complex mimetic robotic arm based surgery and these chores have shown promising results. Our robotic arm is based on an innovative idea which provides help to the less mobile or paralyzed patients. Our robotic arm: Monitor Aided Radio-controlled Mobile Robot (MARCMR) is based on a robotic arm mounted over a moveable shaft, which can move from one place to another place by radio control. It uses simple gripping and dropping process to move the object which will assist paralyzed patients. MARCMR may also be helpful to work as laboratory equipment handing tool. MARCMR is controlled by using RF remote. The robot is also attached with a camera which enhances the real time view of the user. The MARCMR can be fixed by the side of a patient so that they can be able to perform their daily routine tasks and secondly they can be installed at various locations within an area where humans do not prefer to go or it might be hazardous. Keeping in mind the durability and flexibility, the MARCMR is built by using Aluminum, Plastic (PVC) and Iron. It has a wrist, elbow and shoulder joints to provide maximum closeness with a human arm. The joints are controlled with DC motors. The MARCMR revealed encouraging outcome as the patients will be able to perform their tasks with ease and they may also be allocated to the places where humans don’t wish to go.

Kamran Hameed, Muddasir Hussain, Ijlal Shahrukh

Development of a New Method to Monitor Shoulder Girdle Motion for Ballerina with Shoulder Impingement Syndrome Based on DAid Smart Shirt Application

Shoulder impingement is the most common cause of shoulder pain. The ability to control the orientation and movement of the scapula is essential for optimal arm function and pain reduction in young adults with shoulder impingement signs. Smart garments find wide range of healthcare applications, including rehabilitation. One of the main parts of smart garment is the sensing system which can include one or several sensing elements for posture and joint motion control. The aim of present research was to verify the possibility of using DAid Smart shirt to capture and monitor shoulder gridle motion during motor control exercises and during training sessions out of laboratory environment for ballerina with shoulder impingement syndrome. Another aim was to develop method of this Smart shirt using in addition to conventional physiotherapy to reduce right side shoulder girdle elevation. As a monitoring tool, specially designed DAid Smart Shirt had been used. Specifically, embodied textile strain sensors gave possibility to capture spatiotemporally motion, but acquisition system provided visual feedback on the screen of remote electronic device. Conclusions: Designed DAid Smart shirt can be objective and convenient tool for shoulder motion monitoring for both: patient and physiotherapist. Thus, it can be used as effective assisting device to conventional physiotherapy for shoulder girdle motion control.

Guna Semjonova, Janis Vetra, Alexander Oks, Alexei Katashev

Detection of Excessive Pronation and Supination for Walking and Running Gait with Smart Socks

Excessive pronation and supination are gait conditions that could lead to such injuries as ankle sprains, shin splints, Achilles tendinitis and others. Early detection of excessive pronation and supination in running and walking gait are important for injury prevention not only for professional athletes but also for the general population. Unfortunately, the typical equipment necessary for detection of these conditions is relatively expensive and therefore is not widely used by non-professionals. Moreover, most of the typical equipment is either designed for operation under laboratory conditions only or is too bulky and consequently affects the performance of the wearer during the performed activity. This study proposes a method for pronation and supination detection by using smart textile socks with integrated pressure sensors and a specific sensor measurement processing algorithm. Each sock has five sensors, one on the heel, two in the middle and two in the front sole area. These sensors are knit from a conductive thread and have a resistivity inversely proportional to the pressure, which allows monitoring of the feet pressure at different parts during a physical activity. A special pressure vector is calculated from the sensor values to characterize the step. The value of this pressure vector give information about the step and allows detection of excessive supination and pronation in the gait. The preliminary tests demonstrated a significant difference between the pressure vector of a normal gait and gait performed with pronation and supination, thus allowing detection of these gait conditions.

Peteris Eizentals, Alexei Katashev, Alexander Okss, Zane Pavare, Darta Balcuna

Development of a Customized Wrist Orthosis for Flexion and Extension Treatment Using Reverse Engineering and 3D Printing

Hand disability implies impairment and limitation in daily activities, affecting patient’s life quality. Broken bones, congenital conditions or cerebrovascular diseases frequently demand the use of structural support in the form of orthoses. Orthoses are categorized according to their mechanical functions in: static, static progressive or dynamic. While static orthoses are usually made of a single piece and do not allow movement, static progressive and dynamic orthoses are made of a main body with assembled with mechanical elements such as rods, pins, straps, springs, etc., thus allowing a limited amount of movement. Hand orthoses demand a high degree of personalization to suit patients’ anatomy and pathology. A new application of the reverse engineering is proposed. Here is described a new multidisciplinary method for the development of static progressive and dynamic orthoses for the hand for the rehabilitation of hand disabilities. The method involves the image acquisition of the patient’s anatomy and the mechanical design of the orthosis by Computer Aided Design (CAD) software. This method offers a high degree of personalization and the development of low volume hand orthoses with a reduction of weight at low cost by using 3D printing. The case presented on this paper is the design of an original dynamic orthosis for flexion and extension treatment of the wrist. The main body of the orthosis was designed using the data from Computer Tomography (CT) scan images and a CAD software to fit the hand anatomy. Mechanical elements were chosen to provide a variation from 0° up to 90° of extension, and up to 90° of flexion with mechanical resistance to assist in the improvement of the wrist flexor muscles strength.

Leonardo A. García-García, Marisela Rodríguez-Salvador, Marcos David Moya-Bencomo

Development of a Gait System in Hypogravity Simulation for Physiological Studies on Earth and in Space

Running and walking stimulate and maintain the functioning of the musculoskeletal and cardiopulmonary systems, which are responsible for body posture, movement, strength and coordination on Earth and during space missions. This study aimed to develop a low-cost Gait System in Hypogravity Simulation (GSHS) for the study of human physiology. The developed construction consists of 5 subsystems: structural, suspension, simulation, force and communication. The GSHS is formed of a body suspension structure with a treadmill, connected to a force platform, welded upright at one end, with the volunteer suspended by a vest and elastic cables, and positioned in parallel to the ground. The maximum permitted weight for the system is 100 kg, taking into consideration the load capacity of the materials and components. A 72 kg object was pressed against the treadmill to test the force platform, and a motor with two rods and articulated mechanical feet was fastened close to the treadmill, allowing the surface to be touched during the human gait simulation. The results demonstrated the GSHS was able to suspend the object, maintaining it pressed against the treadmill without load variations. The communication subsystem stored and transferred the force platform CPU data to the computer. The force platform presented a 2.84% error in measurement of the object weight (72 ± 2.84 kg). The gait simulation test demonstrated the force platform was able to perform the real-time collection of touch time for each foot and the gait ground reaction forces. The GSHS was able to maintain communication between the force platform and data receiving system.

Ana Karla Oliveira Leite, Thais Russomano, Marlise dos Santos Araújo, Júlio César Marques de Lima

The Options in Robotic Control of Rehabilitating Patient’s Lower Limbs

The use of robotics is currently expanding in all spheres including healthcare. There are many fields of healthcare, where robotics is being or can be used. A design of new rehabilitation devices and aids has to come out from the knowledge of anatomy and physiology of specific body-part movements combined with proper analysis of body movements in particular rehabilitation methods. This article analyses physiological movements in selected rehabilitation methods focused on lower limbs rehabilitation. It also proposes options for realization proprioceptive neuromuscular facilitation by using robotic devices.

Karel Vosahlik, Jan Hosek

Knee and Ankle Powered Above-Knee Prosthesis Design and Development

Amputation has vast influence on life of amputees. Despite technology advancements, above-knee leg amputees still have quite a problem ascending stairs. At Faculty of Mechanical Engineering and Computing, University of Mostar, we are developing above-knee prosthesis that would be able to perform stair ascent in natural manner. The goal is to mimic main leg muscles by using actuators. First tests of the prosthesis showed that it is not enough to power prosthesis using only knee actuator and that in order to achieve more natural stair ascent ankle actuator should be integrated into a prosthesis design. This paper presents our current design of the above-knee prosthesis and its functions. The prosthesis is powered in the knee and in the ankle by hydraulic actuators. With the ankle actuator integrated into the design, prosthesis showed much better results, closer to the natural stair ascent. Current prototype of the prosthesis was designed by using combination of custom-made and off-the-shelf components which proved to be good for initial tests and experimental purposes. However, novel components need to be developed in order to optimize the prosthesis and make its design less rough, more ergonomic and user friendly.

Miljan Rupar, Adisa Vučina, Remzo Dedić

Adaptive Impedance Control of a Robotic Orthosis Actuated by Pneumatic Artificial Muscle

In recent years, rehabilitation robots which help the neurological impaired patient regain the function of the lower limb via training sessions have been developed with great attention. Since these types of robot interact closely with humans, safety is always the top priority considered in the design. Besides, the compliance of the robot must also be controlled to give the subject the best comforts. To fulfill the above mentioned requirements, a two degrees of freedom (2-DOF) robotic orthosis power by pneumatic artificial muscles (PAMs) based on the human musculoskeletal system is developed in this study. The system is able to track any desired trajectories by using a computed torque control strategy. The impedance controller is also integrated into the system to adapt the robot compliance according to the external force. The feasibility and effectiveness of the developed system are verified by experiments.

Quy-Thinh Dao, Shin-ichiroh Yamamoto

Quantifying Movement of the Head and Shoulders During Quiet Standing Using MatLab Software and Promising Parameters

In this paper, we describe a method for quantifying movement of the head and shoulders during quiet standing. The method proposed allows for the determination of postural stability of the head and shoulders, especially during the Romberg’s test, by recording the relative angular movements. The proposed software is used to calculate new parameters of the head and shoulder movements. These parameters are: the area of the confidence ellipse of the inclination of the head versus the inclination of the shoulders and the area of the confidence ellipse of the head rotation versus the shoulder rotation, the size of the main and minor axis of the confidence ellipse of the inclination of the head versus the inclination of the shoulders and the size of the main and minor axes of the confidence ellipse of the head rotation versus the shoulder rotation. The proposed method was implemented using MatLab software. To test this method, we compared the movements of the fourteen healthy subjects/volunteers and nine patients with an inner ear viral infection. Based on the data results, we identified that the parameters can be used to evaluate postural stability in neurology.

Petr Volf, Jan Hybl, Patrik Kutilek, Jan Hejda, Jiri Hozman, Vaclav Krivanek, Radek Doskocil, Rudolf Cerny

Validation of the Novel Body Weight Support System Using Pneumatic Artificial Muscle: A Case Study

Locomotion gait training system plays a significant role in therapy for the patients who are in recovering from hemiplegia, paraplegia, spinal cord injury or after stroke. Modern gait training systems commonly use a Body Weight Support (BWS) system which is to enable the spinal cord injury or stroke patients bearing their weight during the walking practice. The conventional rope-pulley mechanism in conventional BWS systems could cause the “pendulum effect” during gait training and make subject be uncomfortable. Furthermore, using only one rope-pulley mechanism the conventional BWS system could not flexibly modulate the supported force, for example, the hemiplegic patient. This research is aimed to develop a novel BWS system which will be used to support the spinal cord injury patient during gait training. The novel BWS system will be applied Pneumatic Artificial Muscles (PAM) for generating the support force. The mechanical structure of the new BWS system is totally different from the conventional body weight support system. Therefore, the new BWS system will have several advantages, such as simplicity, low cost and flexibly adjusting the unloading force. The purpose is to develop a very simple BWS system for gait training, however, its capabilities generating active unloading forces. An experiment with a perturbation was conducted using the new BWS system and a representative conventional BWS system (Counter Weight system) to verify the performance of the new BWS system and to investigate the gait variance of the subject under both two BWS system. The results showed that the new BWS system presented a better performance in comparison with the Counter Weight system.

Riichi Takiguchi, Van-Thuc Tran, Shin-Ichiroh Yamamoto

Estimation of Postural Control Strategy During Continuous Perturbation

Stability is an important aspect for every moving object and millions of people spend a good deal of their time on their feet for standing, walking, or running. Compared to static balance, dynamic balance with presence of external perturbation requires more complex strategy. The purpose of this study was to investigate the multi-segment of human postural control strategy organization in continuous perturbation balance task between ankle-hip angle as collective variable. We examined the transition of Center of Mass (COM)-Center of Pressure (COP) and ankle-hip angle pattern in moving platform balance paradigm. Eight healthy young adults stood on a moving platform in the anterior-posterior direction continuously within the frequency range 0.2–0.8 Hz and vice versa with eyes opened. COM, COP, and ankle-hip angle changed from in-phase to anti-phase at a certain point frequency of support surfaces. From the cross-correlation coefficient calculation, higher frequency shows negative correlation between the ankle-hip angle which mean these two variables were moving in the different phase direction. These results indicate that joint angle sway also could be one of the collective variables in order to determine postural strategy determination.

Nur Fatin Fatina bt Mohd Ramli, Ogawa Sho, Ikeda Takehiro, Yamamoto Shin-ichiroh

Semiportable Manually Actuated System for Measuring Muscle Spasticity

In the article, we describe a design of a new system which provides means to quantitatively assess passive resistance of skeletal muscles, also termed muscle spasticity. New design is focused on the measurement of muscle groups which are responsible for movement of elbow joint. The semiportable system is an alternative to expensive motorized isokinetic dynamometers. System is manually actuated dynamometer. The electronic subsystem of the system is used to measure angular velocity and torque in the elbow joint. An incremental encoder is used for the measurement of angular velocity. The angular velocity of the rotational movement in a joint is a result of movement effected by manually controlled lever. The lever is controlled by a physician. During the angular movement of the upper limb segments, the elbow joint torque is measured by a strain gauge subsystem. The output from the system is a graphic dependence between the angular velocity and the torque, which is used to evaluate spasticity. The dependence between the passive moment of force and kinematic angular parameters allows us to study complex motion and force possibilities of the joint. The designed system could be useable and widely applicable in clinical practice, as well as research of diseases and treatment of musculoskeletal system.

Barbora Adamova, Petr Volf, Jan Hybl, Patrik Kutilek, Jan Hejda, Slavka Viteckova, Vaclav Krivanek, Radek Doskocil, Jan Farlik, Pavel Smrcka

Position Estimation of an IMU Placed on Pelvis Through Meta-heuristically Optimised WFLC

The estimation of lower trunk orientation and position during normal walking is relevant in clinical setting in order to improve the assessment of walking disorders. In this paper we introduce a new method for the estimation of the position of an Inertial Measurement Unit (IMU) placed on pelvis, during normal walking on a treadmill. The element of innovation is the use of a meta-heuristic optimisation process to estimate the optimal parameters of a Weighted Fourier Linear Combiner (WFLC) filter, which is designed to efficiently extract periodic/pseudo-periodic components of signals. The estimation of WFLC parameters was performed through an optimisation procedure based on the Artificial Bee Colony (ABC) algorithm, minimising the difference between the WFLC reconstructed position and the data coming from a sterophotogrammetry (SP) system. The WFLC weights obtained from the first set of data (training set), with different walking speeds, were then used to improve the estimation of multiple walking trials with the same measurement setup (test set). This approach allows to obtain useful clinical information using wearable, lightweight and low power consuming devices such as IMUs. This method has been validated through SP data, evaluating the Root Mean Square Error (RMSE) between the two system’s position estimations. The results show a global improvement of the position estimation over the three axes both during the training phase and the test phase. A low SD among the RMSEs in the test set, after the filter application, shows a good repeatability of the method over different trials at the same speed.

Stefano Cardarelli, Federica Verdini, Alessandro Mengarelli, Annachiara Strazza, Francesco Di Nardo, Laura Burattini, Sandro Fioretti

Pressure Pulse Wave Velocity and Axial Prestretch in Arteries

The velocity of the propagation of a pressure pulse wave is considered to be a useful marker of the state of health of the cardiovascular system. Many clinical measurements, laboratory experiments and computational simulations have proved that the pressure pulse velocity correlates with age-related changes in the mechanical properties of arteries. Age-related stiffening of arteries, referred to as arteriosclerosis, leads to the increase in the pressure pulse velocity. However, the stress and strain state of an artery is not given solely by its loading and mechanical properties. Arteries are residually stressed that can be seen when cylindrical segment of an artery is excised from the body. The segment retracts because the axial prestretch is released. This prestretch declines with age, as a consequence of the damage accumulated to elastic lamellae during aging. Previous studies have paid little attention to the effect of axial prestretch on the velocity of the pressure pulse wave. The study presented here is based on a combination of a linearized 1D model of the fluid dynamics and the nonlinear anisotropic response of the human abdominal aorta. The model predicts that the application of axial prestretch can significantly change the velocity of the pressure pulse. To be more specific, preliminary results suggest that within the range of physiological pressures, the model that considers initial axial stretch of the aorta predicts lower pressure pulse velocity in comparison with the model that neglects axial prestrain of the tube.

Lukáš Horný, Ján Kužma

Biphasic Rheology of Different Artificial Degenerated Intervertebral Discs

Simulation of the intervertebral disc (IVD) degeneration in animal models is of great interest towards exploration and evaluation of potential regenerative therapeutics. Hence, the objective of this study was to investigate the biphaisc response of the IVD for different artificial degeneration models. Fifty motion segments were dissected from juvenile sheep lumbar spines. The specimens were assigned equally into 5 groups (i.e., (1) intact (I), (2) punctured with a 16-G needle (P), (3) punctured with a 16-G needle combined with fatigue loading (PF), (4) denatured by injecting 0.5 ml 0.25% trypsin solution (T), and (5) denatured by injecting 0.5 ml 0.25% trypsin solution combined with fatigue loading (TF)). Specimens were mounted in a chamber filled with phosphate buffered saline and underwent a stress-relaxation test. Based on linear biphasic theory, the aggregate modulus (HA) and permeability (k) were extracted. Aggregate modulus decreased in P and T discs but increased in PF discs as compared to intact ones. The difference of the aggregate modulus between TF and intact discs was not significant. Permeability decreased in T, PF and TF discs. The permeability of both PF and TF discs was significantly lower than F and T discs, respectively. It is concluded that proposed artificial degeneration models can be used to investigate potential regenerative therapeutics.

Mohammad Nikkhoo, Romina Kargar, Kinda Khalaf

Accuracy Evaluation of 3D Reconstruction of Transfemoral Residual Limb Model Using Basic Spline Interpolation

In this paper, a study on the accurateness of 3D reconstruction for transfemoral residual limb based on Magnetic Resonance Imaging (MRI) using basic spline (B-Spline) interpolation feature is presented. Many researches have constructed 3D models by using the Non-Uniform Rational B-Spline (NURBS) approach; however, almost none of those studies have elaborated in detail the methodology used in the project and the accuracy of the model’s volume against the residual limb volume. This study focuses on the optimization of the residual limb model’s volume by investigating the effect of spline points on the volume value. This project is divided into 3 phases, namely pre-segmentation, segmentation, and 3D reconstruction. However, this study focuses on the segmentation phase in which four different spline point numbers are chosen, namely 72, 36, 24, and 12 points; CAD software CREO Parametric (PTC) was used for this process. A higher number of spline points achieved greater accuracy for the model’s volume. The volume (mm3) of the 3D model with the specified number of spline points was evaluated by comparing it with the volume of the 3D model created by using image processing tools from MATLAB (Math Works). The results show the increment in accuracy of the volume value when the number of spline points is increased. The highest accuracy in terms of volume value is achieved when the model is created with 72 and 36 spline points, with an average error percentage of 6.36%, which realized the hypothesis. The results indicate that CAD software, which is a technical drawing tool, can also be used in the biomedical field to design 3D models of the human anatomy with high accuracy, if the software includes a spline interpolation feature.

Mohd Syahmi Jamaludin, Akihiko Hanafusa

Gait Asymmetry in Winters Group I Hemiplegic Children: Role of Tibialis Anterior

Hemiplegia is a neurological disorder that occurs quite often in children, affecting up to one child in one thousand. Typically, only one side of the body is affected by hemiplegia, while the other side is maintaining an apparently normal behavior. Purpose of present analysis was assessing gait asymmetry in group I (W1) hemiplegic children according to Winters classification, where W1 is characterized by presence of drop foot in swing in the hemiplegic side. Asymmetry was quantified by differences between hemiplegic and non-hemiplegic side in terms of foot-floor contact and electromyographic (EMG) activity. Surface EMG from tibialis anterior (TA) and foot-floor contact data were acquired in ten hemiplegic W1 children during walking to fulfill this aim. An exceptional number of strides was analyzed to consider the data variability, expected in W1 (mean ± SD = 287 ± 62 strides for each child, more than 3000 in total). Statistical gait analysis, a recent methodology performing a statistical characterization of gait, was applied to process EMG data. The research was undertaken in compliance with ethical principles of Helsinki Declaration and approved by institutional expert committee. Results showed that asymmetries were detected in basographic data: W1 children showed a significant decrease (p < 0.05) of strides with normal foot-floor contact (HFPS sequence: heel contact, flat-foot contact, push-off, swing) in hemiplegic side with respect to non-hemiplegic side. Also, TA recruitment presented asymmetries during walking, characterized by a curtailed, less frequent activity (p < 0.05) during terminal swing and a lack of activity at heel strike in hemiplegic side, with respect to non-hemiplegic side. In conclusion, present study suggested that walking in W1 children is characterized by asymmetries in both foot-floor contact patterns and TA recruitment.

Francesco Di Nardo, Alessandro Mengarelli, Annachiara Strazza, Marta Malavolta, Federica Verdini, Stefano Cardarelli, Laura Burattini, Alberto Nascimbeni, Sandro Fioretti

Role of the Visual Feedback on Balance Responses to Upright Stance Perturbations

In this study an evaluation of visual feedback on the balance response to upright stance perturbations is proposed. Subjects underwent to base of support translations in backward direction at fixed velocity in an eye-open (EO) and eye-closed (EC) condition. Center of pressure (COP) and center of mass (COM) were acquired, showing a repeatable double-peak shape which mirrors two different response periods: a destabilizing phase and a counterbalancing phase. Thus, COP and COM were analyzed on the basis of their temporal and spatial features. Further, also the angular displacement of lower limb joints, trunk and head were considered and lower limb muscular activity in terms of myoelectric latencies. Results showed several differences in COP and COM based parameters between EO and EC condition. Moreover, angular range variations seemed to indicate a different role of each joint in the two considered sensory conditions, highlighting the switch from an ankle-based strategy (EO condition) to a more complex kinematic strategy (EC condition). Outcomes of this study could add information about: (A) the suitability of considering COP displacement in perturbed posture analyses with sensory deprivation and (B) the significant role of the visual feedback in balance maintenance when a sudden and quasi-impulsive disruption is employed.

Alessandro Mengarelli, Stefano Cardarelli, Sandro Fioretti, Annachiara Strazza, Andrea Tigrini, Francesco Di Nardo, Laura Burattini, Federica Verdini

Biomechanical Evaluation of the Impact of Different Weight Loading Conditions on the Mechanical Environment of the Hip Joint Endoprosthesis

Total hip arthroplasty (ΤΗΑ) is a reconstructive procedure which restores mobility and relieves pain related to several types of hip arthritis. Obesity is associated with a higher rate of postoperative complications after THA, including poor wound healing, periprosthetic joint infection, instability, and aseptic loosening. The proposed biomechanical study evaluates the effect of different weight loading conditions on the mechanical environment of the hip joint endoprosthesis. The bones were osteotomized and specifically machined for the experiments by an orthopaedic surgeon. Load cycles were programmed to simulate single-leg stance of gait of a normal-weight individual (70 kg) and an overweight individual (100 kg). The discrimination between normal and overweight subjects was based on the standards of the World Health Organization. To measure the micro strains on the femur during single-leg stance of gait, 14 strain gages were positioned on critical stress points of the femur based on the Gruen femoral zones. For all the examined zones, the micro strain values were found to increase with increasing the weight. This indicates that the displacement in the hip joint endoprosthesis is higher for overweight subjects increasing the risk of failure. Also, the mean micro strain difference was higher on the greater trochanter compared to other zones. To our knowledge, this is the first biomechanical study which quantifies the impact of weight loading conditions on the mechanical environment of the hip joint endoprosthesis and for different measurement positions.

Ioannis-Ilias K. Farmakis, Vassiliki T. Potsika, Emilios Pakos, Dimitrios I. Fotiadis

Assessment of Postural Stability Using the Method of Postural Somatooscilography

The aim of article is to present new method for evaluating the postural stability using oscillating platform. Proposed methods are alternative to basic methods which are usually parts of the commercial posturography systems. The methods for calculating the postural parameters have been designed in order to objectively quantify and classify the ability of postural stabilization on a standardized oscillatory platform, and determine differences in the postural stabilization of motor function in healthy people and in people with postural instability. The Posturomed (Haider Bioswing GmbH) and biaxial accelerometer sensor were used for measurement the body acceleration during single leg stance provocation test. The postural somatooscilogram has been defined, which shows accelerations of platform, in horizontal plane in both anteroposterior and mediolateral directions over time. Two parameters, Average Damping Coefficient (ADC) and Average Coefficient of Damped Energy (ACDE), were used to evaluate postural stability. The proposed method was implemented in MatLab sw. Patients with postural disorders and control group of healthy subjects were measured. Statistically significant differences have been observed in postural stability between independent postural stable group and postural unstable groups. Based on the findings, we can say that the presented method allows a complex analysis of the single leg stance in patients with postural balance disorders in clinical practice.

Roman Melecky, Eugen Rasev, Patrik Kutilek, Jaroslav Jerabek, Marketa Janatova, Karel Hana, Jan Muzik, Pavel Smrcka, Jan Kaspar

Quantitative Assessment of Osteoarthritic Knee Instability: Comparison with Conventional Imaging Modalities

Knee osteoarthritis (OA) is the most common musculoskeletal disorder affecting all populations. One common knee OA symptom is instability; thus its assessment could allow diagnosing and following-up of the disease without using conventional imaging techniques, such as plain radiography or magnetic resonance imaging (MRI). Knee kinematic measurements using accelerometers could provide a low-cost and non-invasive option to quantify knee instability. The aim of this study was to assess the relationships between kinematic data, instability parameters derived from the imaging techniques, goniometer-based measurements, and radiological OA stage. The right knees of 66 females (44–67 years) were examined using MRI, plain radiography, and goniometer-based angle measurement. Kellgren–Lawrence (KL) grade and the joint line convergence angle (JLCA) were determined from the radiographs. Cartilage thickness and OA score (MOAKS) were derived from the MRI. A ratio between lateral and medial cartilage thicknesses was calculated from the average thickness of segmented cartilage over the weight bearing area (MRIratio). Accelerometers attached to thigh and shank were used to record kinematic signals during a one-leg-stand test. Power of the accelerometer signals along the anatomical longitudinal axis (Pacc) was used as a measure of knee instability. Finally, Spearman’s correlations between the acquired parameters and KL grade/MOAKS scores were calculated. Leave-one-out cross-validation and logistic regression were used to discriminate OA subjects (KL ≥ 2). All the instability parameters (Pacc, JLCA and MRIratio), except the goniometer angle, showed significant correlations with KL grading (rho = 0.32–0.64, p < 0.01) and MOAKS composite score (rho = 0.35–0.56, p < 0.01). Both Pacc and JLCA showed higher areas under the ROC curve to discriminate OA (AUC = 0.76 and AUC = 0.78) than MRIratio and goniometer angle (AUC = 0.55 and AUC = 0.56). Our results demonstrate the clinical potential of kinematic knee instability measurements using low-cost accelerometers. Such approach could become a potential new tool in OA diagnostics.

V. K. O. Virtanen, J. Thevenot, A. Tiulpin, J. Hirvasniemi, J. Niinimäki, M. Nevalainen, S. Saarakkala

Recent Progress on Preferential Covered Stent Development

Carotid artery stenosis can be treated by carotid endarterectomy operations (CEA) and carotid artery stenting procedures (CAS). Unlike other artery stents, the effectiveness and safety of carotid artery stenting is not prevailing though it has many advantages. Our group has been developing new generation carotid artery stent since 2011. The innovative carotid stent was named as preferential covered stent (PCS) as it could prevent both emboli release at internal carotid artery (ICA) and provide perfusion to external carotid artery (ECA). A series of studies have been carried out to verify the carotid stent design through modeling and simulation, in vitro loop testing, and in vivo pilot animal testing in our previous proof of concept (POC) stage. Here we report some recent findings on PCS development, including simulation and experimental work on stent crimpability, membrane material characterization, and the flow response for different slit designs in vitro.

Fangsen Cui, Gideon Praveen Kumar, Li Buay Koh, Keping Zuo, Hwa Liang Leo, Jackie Pei Ho

Photoelastic Analysis of Shoulder Arthroplasty: Current Descriptive Analysis of Research in Scientific Journals

Shoulder joint complex poses a biomechanical challenge due to its complexity and the number of structures involved. Shoulder pain is one of the most prevalent reasons for consultation in primary health. The main chosen surgical treatments for joint degeneration, as a consequence of the chronic injury of the rotator cuff, is reverse arthroplasty. Photoelasticity is an experimental method used to evaluate the strain environment under mechanical loading. The aim of this study is to present a systematic revision of the literature in academic journals for the period 2000–2017 related to the study of stresses and deformations in the shoulder joint with arthroplasty through photoelasticity technique. To obtain the data, specialised search engines were used: Google Scholar, Scopus, Web of Science and PubMed. Descriptive investigation was performed through a combination of values and boolean algebra. A total of 13 articles were selected, which were reviewed and classified in two categories (photoelasticity analysis in the shoulder joint without prosthesis and study of photoelasticity in the shoulder with arthroplasty). There distribution of articles by year, journal and investigation method was also described. The photoelasticity by stress freezing allows the study of internal zones, something that is not possible with other techniques. The analysis is frequently performed with prosthetic components of total anatomical shoulder arthroplasty, but there are barely any precedents in reverse shoulder arthroplasty. Therefore, new investigations that show the effect of reverse arthroplasty are suggested, since it is present in the treatment of many other prevalent pathologies.

D. A. Almeida-Galárraga, A. Ros Felip, F. Marco Martínez, Laura Serrano-Mateo

A Sliding Mode Control Model for Perturbed Upright Stance in Healthy Subjects

Human upright stance and balance maintenance in quiet conditions have been extensively evaluated throughout the years. However, relatively less information is available on how the central nervous system (CNS) acts to maintain balance after sudden perturbations of stance. Here, a sliding mode control (SMC) model for the characterization of balance maintenance after external perturbations is proposed. Human stance was modeled as an inverted pendulum (IP), which describes kinematics in the sagittal plane; the choice of a SMC allowed to avoid model linearization, commonly employed when using a single-link IP for bipedal stance modeling, thus providing a more accurate description of the human-stance system dynamics. Model was applied on experimental data obtained from perturbed stance trials consisting of a series of disruptions of the same magnitude. This experimental condition was able to elicit a well-known feature called “habituation rate”, which refers to the subject capacity to self-adapt his/her responses to identical perturbations. SMC parameters were identified through a robust optimization procedure. Results showed limited tracking errors for center of mass displacement. One of the SMC parameters exhibited a clear trend from the first to the last trial, appearing able to quantify the habituation rate effect. The application of such a control model to the non-quiet stance can provide additional information in understanding how the CNS tailors balance responses in different conditions.

Alessandro Mengarelli, Sandro Fioretti, Giuseppe Orlando, Stefano Cardarelli, Ismaele Fioretti, Gian Marco Paci, Laura Burattini, Francesco Di Nardo, Annachiara Strazza, Federica Verdini

Could Postural Strategies Be Assessed with the Microsoft Kinect v2?

Quantification of body movement strategies to maintain balance may be useful to understand changes in postural control. Some methods for this purpose require special preparations, such as placement of inertial sensors, goniometers or EMG electrodes. In this study, the capability of the Microsoft Kinect v2, a markerless motion sensor, to assess postural control strategies was tested. Forty-six young healthy subjects had the trajectories of 25 “joints”, provided by a Kinect v2, recorded during upright stance with eyes open or close, on rigid (force platform) and soft (foam pad) surfaces. Postural strategies were characterized by a strategy index (SI) based on the phase difference between the accelerations of upper (trunk) and lower (hip) segments of the body, measured by the Kinect in anterior-posterior and medial-lateral direction. Ankle and hip strategies were identified by in-phase or counterphase accelerations respectively, the phase being estimated from the covariance between 2-s sliding windows of the two signals. The trajectories of center of mass (COM) and center of pressure (COP) were also computed from the Kinect and the force plate, respectively. The SI and the velocities of COP and COM were significantly different between conditions (Friedman p < 0.001 for SI), suggesting effects of sensory information. These results are in line with other studies, showing coexistence of both strategies during stance and the predominance of ankle rather than hip strategy on foam or with closed eyes instead of on rigid surface with open eyes. These results support using the Kinect v2 to assess postural strategies.

Diego Gonzalez, Luis Imbiriba, Frederico Jandre

The Elbow and Forearm Portable Rehabilitation Device

In this paper the design of a new rehabilitation device for the elbow joint and forearm will be presented. In the beginning of the article key requirements (such as mass of the device, movement amplitude, degrees of freedom etc.) will be discussed and established. Then, the design concept of the rehabilitation device will be presented. The main functional and design features, such as two degrees of freedom or placement of bidirectional load cells, will be highlighted and discussed. Key equations connected to the design requirements will be reported. Then, the control system, which included active and passive control mode, will be presented. Finally, an overview of the whole device with full functionality and the plan of further improvements will be given.

Sergei Sokolov, Sergei Krivosheev, Maria Aleksandrova, Roman Iutsis, Roman Olejnik, Stanislav Reznikov

Can Be Minimization of Membrane Bending Energy Used for Simulation of the Nanoparticle-Cell Interaction?

In addition to size, shape plays an important role when nanoparticle interacts with a cell. Mathematical model was formulated to predict membrane elastic energy in the presence of hydrophobic cylindrical nanoparticle. Two states of nanoparticle-phosholipid complexes were studied: the micellar complex with a nanoparticle encapsulated in the phospholipid monolayer and the lamellar complex where a nanoparticle is trapped inside the lipid bilayer. It was shown that there exists a critical size for the cylindrical nanoparticle below which the lamellar state is energetically more favorable. However, the critical size of cylindrical nanoparticle is considerably lower than the one of spherical nanoparticle. It might be concluded, that biological activity of cylindrical nanoparticle in comparison to spherical nanoparticles might be attributed not only to its higher area to volume ratio, but also to lower critical size. Lower critical size prevents a nanoparticle to be trapped inside the lipid bilayer and facilitates its translocation through phosholipid bilayer.

Martin Otáhal, Jitka Řezníčková, Matej Daniel

Fundamental Study of a Simple Walking Support System Using Smart Devices

Accidents involving falling frequently occur and are a particularly serious problem for the elderly. Therefore, prompting and training people to maintain a form of gait with appropriate stride length and foot-ground clearance in daily life are essential to mitigate the danger of such accidents. Herein, we propose a simple walking assistance system designed to prevent falls using a smart device that is worn on the arm. This system can be used in daily life. The smart device is equipped acceleration sensors, which are used for gait decision. When the risk of falling becomes high, the device prompts the user to adjust their gait using notifications such as alarms, vibrations, and flashing lights. To increase the accuracy of decision making of the smart device, we have introduced a decision tree approach. This method was found to accurately classify gait patterns in all but a small number of test participants. Furthermore, we analyzed arm acceleration data during walking and found that significant arm swing is necessary for the users of our proposed system. Taking these considerations, we reconstructed the experimental system using a Microsoft Kinect® v2 sensor to analyze the motion of the test participants in more detail, and preliminary tests of the device were conducted. The system was successful in recording gait and in providing a foot height feedback system for the user.

Nobuyuki Toya, Yutaro Sakamoto, Yu Taguchi, Kodai Kitagawa

Experimental Analysis of Cellular Membrane Mechanical Properties

The study of cell-environment can reveal the possibilities of using nanoparticles in biomedicine. The condition of the cell membrane reflects the mood of whole cell. The membranes as the outer envelope of the cell have a semi-fluid character, and the proteins and lipid molecules are in constant motion. Our aim is to develop methodology for measuring of cell mechanical properties. Atomic force microscopy and force spectroscopy were selected for contact between a tip of cantilever and a cell. This work presents the results of comparison using different tips of cantilevers and verification on several types of cells. Dependence between Young’s modulus of a cell membrane and surface attachment is next part of this work. Different surfaces are creating by coating of glass. Working with living cells claims specific approach in all parts of the research. The results compare the properties of the same cells on different surfaces.

Bohumil Hornát, Martin Otáhal, Jana Turňová

Development of a Modular Bionic Prototype Arm Prosthesis Integrating a Closed-Loop Control System

An active prosthetic arm is not only dependent on critical factors for clinical use, such as weight or bulk but also needs reliable control inputs for accurate and safe positioning. Particularly with a high level of amputation, light but robust devices are essential. Our concept is composed of a modular system, based on bionic design principles, that is adaptable to the specific level of amputation of an arm. By following three basic rules: proximal weight, flexibility and lightweight but silent operation, it is possible to mimic the weight distribution of a human arm. A custom developed control hardware attached on top (HAT) is based on a Raspberry Pi 3 (RPi3) and holds the ADS1299 that is capable of acquiring sensor and other bioelectrical signals. The motion and position data is gathered using a 9-axis inertial measurement unit. Based on the processed data a control signal is sent to the independent actuator control unit. The use of the RPi3 allows performing complex decisions and control algorithms fast enough for real-time control of the prosthesis actuators. The resulting ranges of motion are 120° for the elbow joint and 270° for the wrist joint. The elbow joint can lift a weight of maximal 3.3 kg with a lever of 30 cm through the entire range of motion within two seconds. The system provides a novel bionic design that allows usage not only for transradial but also transhumeral amputation. The proximal weight distribution and the used materials increase the wearing comfort in daily tasks and mimic to a high extent physiological conditions. Furthermore, the speed of the control system is within the range of the electromechanical delay in the human body which not only is beneficial for control purposes but also increases the acceptance of the prosthesis.

Christoph Kast, Bernhard Rosenauer, Helmut Meissner, Weerayot Aramphianlert, Matthias Krenn, Christian Hofer, Oskar C. Aszmann, Winfried Mayr

A Wearable Gait Assessment System for Evaluating Post-stroke Patients’ Rehabilitation

Most of the post stroke patients are common with walking difficulty. The gait pattern could be taken as the severity of the patients. About 88% of stroke patients have certain degrees of hemiparesis. Hemiparesis will attribute to weakness of one side of the body. For post-stroke patients, the rehabilitation is a tedious and long term process. It needs tremendous medical cost and care manpower. Therefore, how to develop a simple wearable device for evaluating the rehabilitation outcome becomes a needful clinical issue. In this study, two wearable devices with accelerometer and gyroscope are placed in both sides of foot. Therefore, the gait patterns can be obtained from the information of both side accelerometer and gyroscope. The gait pattern is also shown in smartphone through wireless techniques. This device can be used to evaluate the rehabilitation outcome and as biofeedback training for stroke patients. The system was tested when normal subject was asked to walk straight in comfortable or self-selected walking speed, but the stride length was limited to 1.2 m. The results indicated stride length closed to 1.2 m. And the symmetry ratio of various spatiotemporal parameters between both feet is around 1.0 which means normal.

C. Y. Wu, Tainsong Chen

Spherical Angular Analysis for Pelvis Coordination Assessment on Modified Gait

This study presents and applies 3D spherical angular analysis in relation with 2D polar coordinates to assess anatomic pelvic movement on modified gait, namely stiff knee (SKG) gait and slow running (SR) comparing with normal gait (NG). Subject specific analysis was performed of an adult healthy male based on inverse kinematics from in vivo and noninvasive capture at human movement lab of reflective markers position from pelvis anatomical selected points with Qualisys camera system during a complete stride of NG, SKG and SR. Radial distance (R), pitch (ψ) and azimuth (λ) angular phases were computed from pelvic angle-angle diagrams (θT, θC, θS) at transverse (T), coronal (C) and sagittal (S) planes, and angular phase (ϕ) and planar radial distance (r) polar coordinates computed from pelvic angle-angle diagrams projections at cartesian planes (θT, θC), (θT, θS), (θC, θS). Average radial distances and phase standard deviation were assessed on spherical and polar coordinates.

Carlos Rodrigues, Miguel Correia, João Abrantes, Jurandir Nadal, Marco Benedetti

Basic Study for 3D Kinematic Measurement of Patella from Single-Plane Fluoroscopic Image Using Intensity-Based 2D/3D Registration

The 3D measurement of dynamic knee kinematics under in vivo conditions is highly valuable for understanding the effects of joint diseases, dysfunction and for evaluating the outcome of surgical procedures. For artificial knee implants, to achieve 3D measurement of the dynamic kinematics, 2D/3D registration techniques which use X-ray fluoroscopic images and computer-aided design model of the implants have been applied to clinical cases. These fluoroscopic techniques have also been applied for motion measurement in joints without implants in recent years, where 3D bone models created from CT or MRI images are utilized. In previous studies, however, the pose estimation accuracy for patella was not sufficient for analyzing 3D knee kinematics, particularly out-of-plane rotation error was relatively large because of small shape and poor geometrical feature of patella. Therefore, this study presents a method to determine 3D kinematics of patella using single-plane fluoroscopic image. The 3D pose of patella is estimated using an intensity-based 2D/3D registration technique, which uses a digitally reconstructed radiography (DRR) image created from 3D bone volume model. The 3D bone volume model for patella was created using CT scan data from a single subject. The 3D pose of the patella model is estimating by maximizing similarity measures between the DRR and fluoroscopic images iteratively with an optimization technique. In order to validate the pose estimation accuracy of patella including femur and tibia/fibura using the intensity-based 2D/3D registration, computer simulation test was performed. A set of synthetic silhouette images was created for each knee model in known typical orientations, and the test was carried out using three similarity measure methods. The result of computer simulation test showed that the root mean square errors were around 1.0 mm, 1.0° except for out-of-plane translation, and the reliability and feasibility of present method was demonstrated.

Takaharu Yamazaki, Yuichi Hayashi, Tetsuya Tomita, Kenichi Kono, Yoshinobu Sato, Kazuomi Sugamoto

Design of Smart Orthosis of Upper Limb for Rehabilitation

Movement problems of the upper limb are a common consequence of many diseases and can drastically affect the daily life impairing normal activities. To regain motor function and muscle power is necessary to treat these diseases with an intense physical therapy. The smart orthosis is an effective and modern method used in the process of muscle rehabilitation. We propose a design of motorized orthosis subsystems for the upper limbs. The orthosis is a motor assist robotic system that, with the help of actuators, will allow the movement of selected parts of the upper limb. The main point is to offer a reliable low weighted exoskeleton with selected sensors to move and control the upper limbs covering 6 motions: shoulder adduction and abduction, shoulder flexion and extension and elbow flexion and extension. The device is a junction of a hard orthosis with a soft orthosis in order to perform passive physical therapist exercises in clinical practice. The actuation is made by Bowden cables connected in one end to the limb and another to a stepper motor located at a backpack carried by the patient decreasing the apparatus weight substantially. The project also includes a selection of sensors comprising accelerometers, strain gages, thermostats, oximeters, that can provide the necessary information to move the limbs quantifying the muscle activity and physical condition through time. Also, a cooling subsystem based on Peltier thermoelectric modules was implemented to control the muscle temperature in case of an inflammatory reaction. The design was certified by kinematic and structural strength simulation using SolidWorks software.

Ana Carolina D´Angeles Mendes de Brito, Patrik Kutilek, Jan Hejda, Pavel Smrcka, Vojtech Havlas

Methods of Motion Assessment of Smart Orthosis of Upper Limb for Rehabilitation at the Clinic and at Home

The aim of this work is to describe proposed and tested methods for evaluation of short-term and long-term movement activity of a smart orthosis for the upper limbs during a rehabilitation process carried out at a clinic or at home. To quantify the description of motion we used methods of evaluation of the time domain data. To test the functionality of the methods, we compared the movement of the dominant and non-dominant limbs, assuming cyclical and acyclic movement, to obtain the expected values for a healthy population. In accordance with the goal, a group of cyclic and non-cyclic movements common to the home environment were proposed. The movements were divided according to the activities performed during sitting, standing and walking. It was: pen writing, typing on the keyboard/using the mouse, eating with a spoon and eating a croissant combing, lifting weights, reading a book, etc. Twenty healthy subjects participated in the study. Four gyro-accelerometers (Xsens Technologies B.V.) attached to the forearms and upper arms of both upper limbs were used to record the upper limb movements. The results show that the calculated values of dominant and non-dominant limb parameters differ significantly in acyclic movements. The smart orthosis which uses the proposed methods can be used to evaluate the physical activity, quantify the evaluation of the rehabilitation process, and thus, it finds use in clinical practice.

Ana Carolina D´Angeles Mendes de Brito, Patrik Kutilek, Jan Hejda, Veronika Kotolova, Vojtech Havlas

Inertial Measurement System for Upper Limb Joints Tracking

This work presents a system for tracking and analysis of upper limb movement through the use of inertial sensors. The designed system uses four inertial sensors, which are placed at the midpoint of the corresponding segments, that is, hand, forearm, arm, and the last one is located between the scapulae and the spine, and between vertebrae T5 and T6 (Thoracic 5 and Thoracic 6). This last sensor is used as a reference point. The information of the four sensors is preprocessed by a microcontroller and sent wirelessly to a computer. The data of each sensor is processed in order to calculate the angular position of each joint. In this work the concept of quaternions is used to avoid the singularities that occur when the reference axes are aligned with the Earth’s gravity axis, instead of working directly with the representation through Euler angles. In addition, a descending gradient filter is implemented to merge the accelerometer and gyroscope data in order to compensate drift errors. To visualize the movement, a simple virtual environment is implemented with SimMechanics®. The designed system is evaluated with 10 volunteers, in flexo-extension and abduction-adduction movements, at different velocities and compared with goniometer measures. The system demonstrates good repeatability and the computed error was less than 3°.

Elisa Perez, Natalia López, Marcos Dominguez, Eugenio Orosco

Estimation of Spinal Loads Using a Detailed Finite Element Model of the L4-L5 Lumbar Segment Derived by Medical Imaging Kinematics; A Feasibility Study

Low back pain is the most prevalent orthopedic disorder and the first main cause of poor working functionality in developed as wells as many developing countries. In Absence of noninvasive in vivo measurement approaches, biomechanical models are used to estimate mechanical loads on human joints during physical activities. To estimate joint loads via musculoskeletal models, the calculation of muscle forces are of importance. It is however difficult to estimate muscle forces as the number of muscles, i.e. unknown parameters, is far more than the existing degrees of freedom; the system is highly redundant. Therefore, in this study, instead of muscle forces estimation, their effects (i.e., rotations and displacements) is measured by medical imaging techniques and prescribed to a detailed finite element model of the L4-L5 spine segment to determine intervertebral disc pressure as a representative of compressive forces acting on the joint. A previously validated geometrically-detailed passive finite element model of the L4-L5 segment was used. Disc, facet joints, vertebrae, and ligaments were simulated with appropriate elements/material properties. Rotations and displacements of the L4 and L5 vertebrae from supine to upright and from upright to trunk flexion of 10° were measured via X-ray imaging. The kinematics were prescribed to the L4 and L5 centroids. Maximal intradiscal pressure of ~0.45 MPa was predicted for the simulated tasks that was in agreement with in vivo data in the literature. Preliminary results indicate feasibility of this kinematics-based approach to predict in vivo spine loads.

Mohammad Saber Hashemi, Navid Arjmand

Upper Limb Motions Analysis for Development of an Upper Limb Rehabilitation Robotic System

The therapists from Prokinetic Rehabilitation Clinic identified the need of a passive rehabilitation robotic system with 3 degrees of freedom for the upper limb. This paper presents the work for the design and development of this kind of rehabilitation robotic system. This project aims to use a user-centered design process to create an upper limb rehabilitation robotic system for patients and therapists from Prokinetic Rehabilitation Clinic. The end-users are and will be involved actively, continuously throughout the system design, development and testing. Upper limb motion analysis has been done using the Vicon system, for simple motions and for functional motions. The positions, velocities and accelerations of each interest joint were obtained. We used this analysis in order to implement the control algorithms for the rehabilitation procedures with an upper limb rehabilitation robotic system. We designed the mechanical, actuation and control systems for this upper limb rehabilitation robotic system.

Dorin Popescu, Cristian Petre Copilusi, Horatiu Roibu, Mihnea Ion Marin, Ligia Rusu, Livia Carmen Popescu

Minimum Invasive Surgery, Robotics, Image Guided Therapies, Endoscopy

Frontmatter

Virtual Biopsies with Handheld Dual-Axis Confocal Microscope

We demonstrate a novel microelectromechanical system (MEMS) based Dual-Axes confocal (DAC) microscope in a 10-mm diameter handheld package. Miniaturization is achieved by using a barbell-shaped, gimbaled, two-dimensional (2-D) MEMS scanner that is actuated by self-aligned vertical comb actuators. The maximum DC optical scan angles are ±4.25° on the inner axis and ±1.5° on the outer axis, and the corresponding resonance frequencies are 3.4 and 1.2 kHz. The maximum imaging rate is 5 frames/s. The miniature DAC microscope operating at 785-nm-wavelength achieves full-width-half-maximum (FWHM) transverse and axial resolutions of 4.5 μm and 5 μm, respectively.

Wibool Piyawattanametha

Augmented-Reality Surgical Navigation System for Better Healthcare Visualization

Nowadays, good medical services are located in the high-level hospitals. The uneven regional distribution and the unbalanced medical quality between different hospitals bring obstacles to patients for better healthcare. In the community hospital, surgeons may lack advanced surgical skills. Considering the clinical needs, we present an augmented-reality (AR) navigation system using 3-D image overlay technology for better healthcare visualization. Autostereoscopic 3-D images of anatomic structures, which are reproduced by employing integral videography technology, are superimposed on the patient via a half-silvered mirror to form an AR navigation scene. The proposed system can generate the vivid autostereoscopic 3-D medical images and realize in situ image overlay, which eliminates the hand-eye coordination problem. By using our system, surgeons can intuitively observe the operative area, the marked high-risky tissue, surgical tools and surgical planning pathway, which make the surgical operation more convenient and intuitive. To consider the demands of clinical applications, we design a new semi-streamlined prototype combining adjustment mechanism and servomotors, which can broaden the visual field. Results illustrate that the navigation system can enhance the surgeons’ operation of the facilitation, as well as the design is more integrated and commercialized, which are more suitable for clinical applications. It is advanced to realize remote visual display and intuitive guidance to solve the uneven distribution of medical resources. What’s more, the system can be used for surgical skill training under the guidance of the 3-D images. Thus, the AR system is beneficial to healthcare, especially in the resource-scare communities.

Boyu Zhang, Longfei Ma, Xiaofeng Qu, Xinran Zhang, Hongen Liao

An Automatic Preoperative Path-Planning Algorithm for Neurosurgery Using Combined MRI and DTI

Background: The structure of brainstem is very complex, and the surgical path planning for surgical navigation system can reduce the damage of the important tissue. We proposed an automatic preoperative path planning method based on combined magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) for determining optimal surgical paths in brain stem tumor surgery. Methods: First, we register the DTI into the MRI by comprehensive considering three type’s information of trace, fractional anisotropy and relative anisotropy to achieve more accurate DTI location information. After that, the optimal solution model of the preoperative path which computes a cost function associated with each point on the outer brain boundary and instrument entry path, is constructed by the gravitational repulsion model and spline interpolation using the segmented model of brainstem and fiber bundle. Furthermore, the preoperative path can be achieved automatically by optimizing the solution of the cost function, and the results are evaluated by comparing the cost of a particular path associated with each critical structure, as well as the total number of examining all the cross-sectional images orthogonal to this path. Results: Our method could complete automatic preoperative path planning and avoid important tissue damage with less cross-sectional images orthogonal to the planning path.

Jia Liu, Miao Li, Fang Chen, Changcun Pan, Xinran Zhang, Liwei Zhang, Hongen Liao

A Low-Cost Pedagogical Environment for Training on Technologies for Image-Guided Robotic Surgery

This research presents a novel low-cost pedagogical environment oriented to ease the use experiential learning methods for training on image-guided robotic surgery technologies. The environment proposes a simplified surgical simulation use case: the movement of insertion and extraction of a needle, similar to an image-guided biopsy situation. The training environment is composed of a 3D-printed phantom, a CT scan of the phantom, a virtual reality environment that includes haptic information, an ad hoc 1 degree of freedom (DOF) robotic system for insertion/extraction and a Novint Falcon, a low cost 3 DOF manipulator that allows achieving haptic feedback. A first pilot experience has been carried out in the “Surgical Simulation and Planning” course of the Bachelor of Biomedical Engineering at Universidad Politécnica de Madrid (UPM). Results of the surveys carried out (by teachers and learners) show that the new project-based methodology improves in all cases the values of student’s satisfaction obtained using the classical methodology based on master classes and practices.

B. Rodríguez-Vila, A. Gutiérrez, M. Peral-Boiza, H. Ying, T. Gómez-Fernández, E. J. Gómez, P. Sánchez-González

Diagnostic and Therapeutic Instrumentation

Frontmatter

Analyzing Rheoophthalmic Signals in Glaucoma by Nonlinear Dynamics Methods

We assess the possibility to analyze signals of transpalpebral rheoophthalmography (TP ROG) by methods of nonlinear dynamics and find out how informative this technique is in examining patients with various stages of primary open-angle glaucoma (POAG). The technique was verified on the basis of TP ROG signals obtained in examining 4 groups of subjects: (1) control group (10 eyes with no ocular pathology), (2) stage I of POAG (15 non-operated eyes), (3) stage II of POAG (7 eyes), and (4) stage III of POAG (4 eyes). In all, 36 eyes of 28 subjects aged 25–84 (average age 62.1 ± 7.1 years) were examined. The analysis of TP ROG signals included determining the rheographic index (RI), calculating the RI average in each group, and finding out how RI depends on POAG stage. Alternatively, we used the nonlinear dynamics method with the signal’s attractor reconstruction, where we chose the time delay, determined the embedding dimension, and constructed the attractor in the space of the chosen coordinates. After the barycenters of each reconstructed attractor were found, we analyzed TP ROG signals graphically in the attractors’ representation plane. The analysis of TP ROG signals by nonlinear dynamics methods demonstrated that a more distinct differentiation of POAG stages as compared to traditional signal processing becomes possible. As the stage of the diseases advances, the location of the barycenter of the reconstructed attractor is changing significantly. It shifts rightward and upward in the space of the chosen coordinates. Due to this fact, it becomes possible to separate TP ROG signals into POAG stages by simple geometric figures and to increase the accuracy of the diagnosis at early stages of the disease, which may be used for further study of the link between the hemodynamic state of the eye and glaucoma stages.

P. V. Luzhnov, D. M. Shamaev, A. A. Kiseleva, E. N. Iomdina, D. D. Khoziev, O. A. Kiseleva, A. P. Nikolaev

Validation of a Wireless and Portable EEG Acquisition System with Dry Electrodes

The Electroencephalogram (EEG) is the non-invasive record of electrical cerebral activity. It is used commonly in sleep studies and in the diagnosis of brain diseases and injuries. In order to reduce noise in the acquisition process and enable new EEG applications such as BCI and home polysomnography studies, we carry out the design and manufacture of a portable wireless system for acquisition of EEG signals. In this paper, we carried out the validation of the system designed by comparing signals acquired with commercial EEG equipment from the AKONIC company. Different EEG recordings were obtained in 4 healthy adult subjects using standard Ag/AgCl cup electrodes and dry electrodes TDE-200 from Florida Research Instruments. Also, we performed the analysis of the acquired signals in eyes-closed and eyes-open resting condition. We conclude that the designed system has low noise levels (0.147 μVRMS and 0.984 μVp-p) and a signal quality comparable to that of commercial equipment, which allows its use in research tasks and portable studies. On the other hand, we observe that the quality of the signal obtained with the dry electrodes is worse, due to the high skin-electrode impedance, but even so it is good enough to detect the eyes-closed and eyes-open resting condition, allowing a more comfortable use of the system.

G. E. Cañadas, C. R. Dell’Aquila, A. Garces, E. Laciar

A Bioimpedance-Based Cardiovascular Measurement System

Bioimpedance measurement is a biomedical technique to determine the electrical behavior of living tissue. It is well known for estimating the body composition or for the electrical impedance tomography. Additionally to these major research topics, there are applications with completely different system requirements for the signal acquisition. These applications are for example respiration monitoring or heart rate measurements. In these cases, very high resolution bioimpedance measurements with high sample rates are necessary. Additionally, simultaneous multi-channel measurements are desirable. This work is about the hardware and software development of a 4-channel bio-impedance measurement system, whereat all channels are galvanically decoupled from each other. It is capable of measuring 1000 impedance magnitudes per second and per channel. Depending on the chosen measurement configuration, impedance changes down to mΩ ranges are feasible to be detected. To enable the usage in a variety of different research applications, further biosignals like photoplethysmography, electrocardiography or heart sounds can be acquired simultaneously. For electrical safety purposes, an implemented galvanically isolated USB interface transmits the data to a host PC. The impedance measurements can be analyzed in real-time with a graphical user interface. Additionally, the measurement configuration can easily be changed via this GUI. To demonstrate the system’s usability, exemplary measurements from human subjects are presented.

Roman Kusche, Sebastian Hauschild, Martin Ryschka

Aortic Pulse Wave Velocity Measurement via Heart Sounds and Impedance Plethysmography

The determination of the physical characteristic of the human arterial system, especially the stiffness of the aorta, is of major interest for estimating the risk of cardiovascular diseases. The most common measurement technique to get information about the state of the arterial system is the pulse wave analysis. It includes the measurement of the pulse wave velocity inside the arteries as well as its morphologically changes when propagating through the arteries. Since it is difficult to detect the pulse wave directly at the aorta, most available devices acquire the pulse wave at the extremities instead. Afterwards, complex models and algorithms are often utilized to estimate the original behavior of the pulse wave inside the aorta. This work presents an impedance plethysmography based technique to determine the aortic pulse wave velocity. By measuring the starting time of the pulse wave directly at its origin by the acquisition of heart sounds and the arrival time at the end of the aorta non-invasively via skin electrodes, unreliable complex models or algorithms aren’t necessary anymore to determine the pulse wave velocity. After describing the measurement setup and the problem-specific hardware system, first measurements from a human subject are analyzed and discussed.

Roman Kusche, Arthur-Vincent Lindenberg, Sebastian Hauschild, Martin Ryschka

Respiration Monitoring by Combining EMG and Bioimpedance Measurements

A common technique to measure diaphragm electrical activation is the acquisition of the occurring electromyography signals using surface electrodes. A significant problem of this technique is its sensitivity against motion artifacts. Forces or vibrations can influence the electrode skin contacts, which generate changes of the electrodes’ half-cell voltages as well as the electrode skin impedance. Both effects result in noise in the same frequency range as the typical electromyography signal and therefore it’s hard to separate these distortions from the desired signal. Another technique to detect muscle contractions is the electrical impedance myography. By applying a small alternating current to the tissue of interest and measuring the occurring voltage drop, the bioimpedance is determined. It contains the information about muscle contractions and relaxations. The major advantage of this technique is, that the impedance information is coded as the amplitude modulation of that voltage drop. The frequency of the excitation current is typically chosen in the range of tens of kHz and thus can easily be separated from the above mentioned artefacts. This work describes a measurement setup which is capable of acquiring electromyography as well as bioimpedance signals simultaneously, sharing the same electrodes. An analog circuit is presented which combines the information of both measurement techniques, allowing their common analog-to-digital conversion by a single converter. The system is capable to acquire 1000 bioimpedances/electromyography samples per second with a resolution of 24 bits. First measurements show that signal distortions, caused by vibrations at the electrodes, are attenuated significantly in bioimpedance measurements.

Roman Kusche, Martin Ryschka

Investigation of a Possibility of ECG and PPG Common Measurement

Electrocardiography and Photoplethysmography are basic investigative methods used in healthcare. As the ECG and the PPG are non-invasive methods. The principle consists in ECG recording of electrical activity of the heart and the result of this sensing is a graph plotting—electrocardiogram. PPG is one of the main methods of measurement plethysmography when the result is a graphic record of pulse wave. The main function of PPG is the volumetric flow measurement of blood (e.g. in atherosclerosis, which is possible by vascular permeability derive their rigidity). Both of these methods are used for monitoring of cardiovascular system. It would be advantageous to have possibility to measure ECG and PPG from one place on human body. It would be also advantageous to have only one device and reduce number or size of sensors or electrodes. In this paper we describe developing such system and also investigation the ideal place for placing of sensors for satisfactory measurement.

Lukas Peter, Antonino Proto, Martin Cerny

Wearable Pulse Wave Monitor Resistant to Motion Artifacts

The aim of this study is to create a wearable device for long-term pulse wave monitoring as well as to investigate the possibility of using adaptive noise cancellation approach for reducing motion artifacts occurred during the real-life recording. In our study wearable monitoring device have acquired pulse wave by using photoplethysmography approach and human movement with triaxial accelerometer. The electrical design of wearable device was based on synchronous demodulation and using 24 bits sigma-delta analog-to-digital converter. To achieve effective and robust motion artifacts reduction we create the pulse wave signal processing method based on band-pass filtering and adaptive noise cancellation. Pulse wave signals were initially pass-band filtered at 0.5–10 Hz to remove noise, electrical and physiological interferences, using a zero-phase forward and reverse digital filter, which first filtered the raw signal in the forward direction, and subsequently filtered the reversed signal, thus the resultant signal has zero-phase distortion. Adaptive noise cancellation was implemented by using a recursive least squares algorithm based on the solution of the Wiener-Hopf equation. Our studies have shown that the best results of pulse wave signal processing are achieved for the following parameters of the algorithm: the forgetting factor of 0.99; filter order of 16. Performance of proposed processing technique was evaluated by assessing signal-to-noise ratio (SNR) of the filtered signal and compared with other approaches such as wavelet multiresolution decomposition and moving average filtering. For correct estimation of SNR we used robust approach based on the eigenvalues of signal autocorrelation matrix. This study indicates that designed wearable device based on principles of photoplethysmography for unobtrusive and noninvasive recording of pulse waves and using advanced digital processing technique for removing motion artifacts could provide an effective and performance tools for improving the long-term healthcare monitoring of human vital signs.

A. A. Fedotov, S. A. Akulov

Restricted Interest-Based Adaptation of Avatar for Interaction with Children with Autism Spectrum Disorder

This article presents a systematic process to develop technological supports for children with Autism Spectrum Disorder (ASD), based on restricted interests. With the information generated from the diagnostic evaluations applied to a group of children with this disorder, were selected avatars that match their preferences. To do this, mobility was added with the aim of being used as a base in the development of therapies that promote the interaction and learning processes of children with ASD. This adaptation increases the children’s acceptance of the avatar, unlike other empirical processes that require an intermediate stage of acceptance.

Luis Fernando Guerrero-Vasquez, Dennys Landy-Rivera, Geanina Ávila, Jack F. Bravo-Torres, Martín López-Nores

Design and Implementation of Digital Tele Stethoscope

Our project relates to Tele-stethoscope which is specially designed to provide state of art technology to medical and health professionals to provide best possible practices to the seniors, people with disabilities, and people in distant areas who may have difficulties to grab a proper health care facility. Initial stage of this project was to consult our professors, health professionals and sketch a concept design. Even though, electronic stethoscopes are available in market but they are out of reach of a common man. We revisited the cost and put up a cost analysis which has turned this instrument more economical. Research was completed to identity the frequencies of head sound which stethoscope needed to filter. The concept includes all the attributes that a Tele-stethoscope should include. Next step was to design analog circuit which comprises pre-amp and post amp stages and then the interfaced to Pc via a free open source. Project was then tested with the help of Skype voice call messenger and we successfully transmitted cardiac sounds with such high quality and precision.

Ijlal Shahrukh Ateeq, Kamran Hameed, Malik Khowaja, Sana Hyder Khan

Impedance Spectroscopy Method to Detect Pelvic Floor Muscle Damage—A Feasibility Study

Impairment of the pelvic floor muscles and fecal incontinence affect 5–10% of the adult populations of European states. The most common cause is perinatal obstetrical anal sphincter injury (OASI) resulting from vaginal delivery. There is no method for screening in the period immediately after delivery. Diagnosis is limited to physical examination. The gold standard, transanal ultrasonography and manometry, can be performed after a few weeks, whereas clinical practice requires that injury be detected as early as possible for optimal treatment. Therefore, we would like to validate an alternative technique, impedance spectroscopy. The aim of the study is to analyze the accuracy of problem detection within the 3–1000 kHz frequency range in 3 radial positions. 22 females (10 issued and 12 included in a control group) were engaged. Impedance moduli and phase shifts were estimated using a bipolar impedance spectrometer along with a specific anal probe. We calculated parameters assessing different subranges of analyzed frequencies and treated them as input vectors for detection. Accuracies were estimated for Naïve Bayes, Random Forest, Support Vector Machine and Quinlay’s C5.0 models. We performed recursive feature elimination to find the most significant subranges of frequencies. An accuracy of 86.4% was observed for the Random Forest technique and entire set of considered parameters. It appears that impedance spectroscopy allows assessment of problems with pelvic floor muscle (particularly OASI), directly after vaginal delivery and faster and easier than gold standard methods.

Marcel Młyńczak, Katarzyna Borycka-Kiciak, Małgorzata Uchman-Musielak, Adam Dziki

Behavior of Electrical Resistance in Gastrocnemius Muscle of Rats During Contractions with Different Intensities

Changes in skeletal muscle electrical resistance during muscle contraction may be associated to two main factors. Changes at muscle morphology e.g. length, volume or cross-sectional area; and changes in its impeditivity, related to changes of biochemical and physiological processes during muscle activity. However, the mechanisms by both morphological or metabolic parameters and, more importantly, if they increase or decrease electrical impedance parameters is yet controversial. The present study aimed to investigate the behavior of the muscular electrical resistance of the gastrocnemius muscle of Wistar rats during muscle contraction at different levels of force. To address that, tetrapolar invasive needle electrodes were placed in the animal muscle for impedance measurement, while two other needles electrodes were placed on muscle ends to electrical stimulate the muscle and evoke contraction. The experimental protocol consisted of ten pulse trains with 1 s duration with 40 s rest using randomized frequencies. All the procedures were approved by the Institutional Ethics Committee for Research with Animals under the decision number 019/15. Results show a decrease on muscle resistance during contraction. It was observed a correlation of r = −0.76 between the intensity of muscle contraction and resistance changes. Our findings suggest that resistance decrease is expected for invasive measurements in healthy muscles. Also, indicates that different changes at resistance amplitudes can be linked with metabolic processes. However, morphological influences cannot be neglected.

A. B. B. Coutinho, J. P. Wereneck-de-Castro, A. V. Pino, M. N. Souza

Personalization of the Oscillometric Blood-Pressure Measurement

Oscillometric blood-pressure (BP) measurement can result in substantial error depending on the physiological parameters of the tested person. Especially the rigidity of the arteries can influence the oscillometric amplitudes. Personalization can greatly improve the accuracy and reproducibility of the measurement. The personalization process requires several measurements taken from a person applying special cuff pressure (CP)—time functions. A BP measuring device was developed to generate different CP—time functions. It is able to sustain the CP at a constant value during both inflation and deflation. The device also measures ECG in Einthoven I lead and photoplethysmographic (PPG) signal at the fingertip. This makes possible to calculate the pulse wave transit time (PWTT). The sampling frequency is 1 ksample/s thus PWTT values are calculated with 1 ms resolution. Recordings were taken from ten healthy subjects, both senior and young ones. The deflation was stopped and the CP was held constant at 90 mmHg and then at 60 mmHg for 60 s each. The subjects were at rest. Pulse wave transit times were determined from the heart to the cuff (PWTTHC) and to the fingertip (PWTTHF). Mean value as well as the trend of change of PWTTHC and PWTTHF over the 60 s intervals with constant CP are person specific, not age-group specific. The change in PPG signal amplitude resulting from cuff occlusion was found to be substantially smaller for senior than for young persons. As a result of the personalization it is possible to define a specific CP—time function providing information not only on actual BP but also on the rigidity of the brachial artery. The recordings taken with constant CP parts help also compensate the effect of breathing.

P. Nagy, Á. Jobbágy

Presence of Stochastic Resonance in Isolated Mouse Heart

The heart is an organ with a continuous activity whose heart rate and strength contractions are modulated by several mechanisms including the autonomic nervous system, the renin–angiotensin system, vasopressin, among others. In particular, the nervous system transmits electrical signals to the heart through neurons. Neurons are essentially noisy. During the past years, several researchers have suggested that the nervous and cardiovascular systems appear to leverage the noise to improve information transfer. Stochastic resonance (SR) is a phenomenon observed when increases in levels of noise cause an increase in any metric of the quality of signal transmission or detection performance, rather than a decrease. In the cardiovascular system, some researchers have suggested that SR could enhance the homeostatic function of the human blood pressure regulatory system, and also SR is present within the baroreflex human center. However, few researchers have addressed in the fact that the noise can enhance contractile response in the whole heart. This study focuses on the electrical stimulation-contractile response coupling and demonstrates experimentally that the noise can enhance the contractile response in the whole heart. Experiments were conducted in isolated mouse hearts (0.040 kg, n = 7) where the contractile response due to an electrical stimulation (3–6 V, 6–17 Hz) perturbed with Gaussian noise was recorded. A Langendorff preparation was used to obtain two variables: the heart rate driven by the pacemaker in the sinoatrial node, and the contraction force, since the force is measured through a suture and a force-transducer placed at the apex of the heart. To the best of our knowledge, this is the first experimental test in whole heart focused on analyzing the contractile response due to electrical stimulation perturbed with Gaussian white noise. We found that the best performance was obtained with 10% induced noise. We have experimentally demonstrated the SR in isolated mouse heart.

Alberto Peña-Romo, Amelia Ríos-Rodríguez, Bruno Escalante-Acosta, Jesús Rodríguez-González

Feasibility Study of Evaluation of Therapeutic Effect for Sleep Apnea Syndrome Using Mental Healthiness Evaluated from Voice

Dealing with sleep apnea syndrome (SAS) is important because of its social burden, however current standard diagnosis requires a costly examination (polysomnography, PSG). Therefore, strong demand for easy screening methods for SAS exists. There is also a need for evaluation of therapeutic effect by continuous positive airway pressure (CPAP). Because CPAP requires adjustment of parameters (titration), or CPAP used inadequately will not improve a patient’s symptom. Considering quality of life, evaluation of therapeutic effect requires monitoring of mental and physical conditions in daytime. We already reported that mental healthiness evaluated from voice, called “vitality,” showed some correlation with severity of SAS. In this study we examined feasibility of vitality as an index of therapeutic effect by CPAP. We recorded voices from subjects when they were examined by PSG for first diagnosis and titration, before and after each examination. Then we evaluated vitality of the subjects at the recording. The subjects were categorized into two groups; subjects of a group started using CPAP after titration, and subjects of another group started using CPAP before titration. As results, direction of change in vitality in the former group varied by subjects at titration, while vitality in the latter group showed tendency of improvement. Within the latter group, the change in vitality tends to get larger as usage rate of CPAP before titration is higher. This result suggests that vitality has a potential for an easy method to evaluate therapeutic effect for SAS, and that diligence of CPAP usage is important for effective treatment.

Mitsuteru Nakamura, Shuji Shinohara, Yasuhiro Omiya, Shunji Mitsuyoshi, Masakazu Higuchi, Naoki Hagiwara, Takeshi Takano, Hirosuke Danno, Shun-ichi Tanaka, Shinichi Tokuno

Finite Element Mapping for Efficient Image Reconstruction in Rotational Electrical Impedance Tomography

Electrical impedance tomography (EIT) is a label free harmless imaging method capable of imaging differences in electrical conductivity of a sample. In EIT, a low frequency current is injected into the sample, voltage differences on sample surface are measured, and from these measurements, interior conductivity distribution is reconstructed. To increase the accuracy of reconstruction, rotational EIT (rEIT) has been proposed where independent measurements are taken from multiple rotational positions around the sample. However, the benefit of conventional electrode configurations are limited to small number of rotational positions. We have presented an approach called Limited Angle Full Revolution rEIT (LAFR-rEIT) that uses a small number of electrodes and large number of rotational measurement position measurements over 360°. The results are comparable to previous rotational EIT implementations, and furthermore, the limited EIT boundary access provides space for simultaneous attachment of other measurement modalities. On the other hand, the increased number of measurement positions cause an increase in computational complexity, and optimization is required until 3D applications are feasible. This work presents modifications into finite element mesh presentation of the imaging domain and outlines an optimization, that enables sufficiently light rotation for 3D LAFR-rEIT computations.

Olli Koskela, Mari Lehti-Polojärvi, Aku Seppänen, Edite Figueiras, Jari Hyttinen

Multifunctional Photoplethysmography Sensor Design for Respiratory and Cardiovascular Diagnosis

Photoplethysmography (PPG) is a transcutaneous optical signal acquisition method to monitor blood volume variations to assess cardiovascular health. Using a light source and a photodetector, PPG signals can be acquired and used in a vast application area. For the estimation of vital parameters like respiratory and heart rate, different properties of this pulsatile wave need to be further analyzed. This demands the utilization of different sensor techniques to be used like motion sensors, skin temperature monitoring and different wavelengths of light sources. This paper represents the proposed multipurpose PPG sensor design, called SmartPPG, which is able to measure multi-wavelength PPG from different skin penetration depths as well as skin temperature while providing motion tracking via an accelerometer. The manufactured prototype was tested for different PPG techniques to evaluate its applicability for arterial, venous and respiratory diagnosis.

Durmus Umutcan Uguz, Boudewijn Venema, Steffen Leonhardt, Daniel Teichmann

Microwave and Impedance Spectroscopy as a Useful Tool for Testing Dielectric Properties of Glucose Solutions

Diabetes is one of the most common social disease in the world. Due to the patient discomfort associated with sample collection using a commercially available devices, there is a great need to design a more favorable and precise sensor of blood glucose level. Promising techniques are based on the correlation between glucose-induced variations and blood dielectric properties. This report presents two possible methods showing the variations of impedance modulus and relative permittivity values in glucose-sodium chloride (0.9%) and glucose-bovine plasma solutions at different concentrations, ranging from 50 to 500 mg/dl, occurring in human blood. It is worth noticing, that in each sample the dielectric properties depend on the glucose concentration of the sample over the whole studied range, that is 1 kHz–2 MHz for impedance measurements and 100 MHz–5.5 GHz for microwave spectroscopy. The experimental results as well as discussion of the results, are presented in this paper.

Izabela Osiecka, Tadeusz Pałko

Changes of Body Composition and Bioimpedance During Pregnancy—Pilot Study in Czech Republic

Monitoring of specific physiological values during gestation process is a very important process. Body composition values and directly measured bioimpedance values however are currently not included into this monitoring although these values can help to track healthy process of gestation. In this work we are presenting new possible measurements of progress of body composition and electrical values during whole gestation process in Czech population. Bioelectrical resistance, reactance and body composition values were measured by BIA device Tanita MC 180 MA on 5, 50, 250 and 500 kHz. BIA measurements from 10 women were evaluated during second and third trimester of pregnancy. We discovered changes in directly measured electrical values and calculated values during a gestation period. Statistically significant increase was discovered in calculated body composition values: Weight (kg) (P = 0.005), Fat mass (kg) (P = 0.01), TBW (kg) (P = 0.005). Statistical significant (P = 0.05) decrease on all used frequencies was discovered in resistance and reactance values. Average decrease of resistance across all frequencies was 73.17 ± 7.62 Ω which presented 11.92 ± 0.07%. Results suggest that body composition values and especially directly measured values that are not equation dependent can give precise description for gestation process and can be used as one of the markers of healthy gestation process in future. Hence this measuring and evaluating of directly measured electrical values and body composition values can give us more information about gestation process.

J. Hlubik, K. Radocha, L. Lhotska, L. Hruban

On the Monitoring of Breathing Volume, Using Textile Strain Gauges

Necessity to attach measurement device to the patient mouth makes use of spirometry difficult for continuous breathing volume monitoring in non-hospital applications. There were number of attempts to replace spirometry with measurements of the trunk volume. One of the potential solutions is evaluation of the breathing volume using set of respiratory belts, placed around the chest to measure changes in trunk circumference. Such belts could be made of the highly strain—sensitive knitted resistive fabric, integrated into tight underwear, like T-shirt or compressive body. The objective of the present research was to check usability of the garment—integrated knitted strain gauges for evaluation of the breathing volume. The breathing monitoring garment have been made in a form of T-shirt with seven knitted resistive stretch sensing ribbons, sewn around the T-shirt trunk and calibrated to measure circumference. Circumferences were used to estimate trunk volume of four healthy volunteers (2 male 2 female). Alongside, volunteers breathing volume was measured using commercial spirometer. The results demonstrated that T-shirt, being calibrated irrespectively to measured individual, could evaluates breathing volume with the uncertainty of 0.6 l, given all 7 ribbons are used for calculation of volume. The individual calibration of the T-shirt for particular individual could reduce uncertainty up to 0.3 l.

Artyom Rozevika, Alexei Katashev, Alexander Okss, Janne Mantyla, Rene Coffeng

Application of Garment—Embedded Textile Electrodes for EIT Based Respiratory Monitoring

Electrical Impedance Tomography (EIT) is a technology capable of supplementing spirometry in a number of applications due to the ability to evaluate regional changes in lung volume. EIT measurements require an array of conventional bio-potential electrodes attached to the patient’s chest. Replacement of conventional electrodes with knitted conductive textile electrodes integrated in a patient’s undershirt could increase the area of EIT applications such as daily respiratory monitoring in hospitals, at home, during physical activity, etc. The goal of the present paper was to demonstrate the usability of textile electrodes for EIT measurements. The conductive textile was integrated in the chest of a long sleeves thermal undershirt to form three rows of 16 circumferential electrodes that can be connected to a commercially available EIT monitoring system. Two healthy male volunteers aged 45–50 performed tidal breathing, deep breathing, and FRC maneuvers. The breathing volumes and FRC were measured using a body plethysmograph. The course of measurements demonstrated that contact between skin and textile electrodes are not tight enough to operate with the EIT device. Applying additional pressure to the electrodes and the use of electrolyte spray reduced the impedance of the textile electrodes to adequate values. Under such conditions, there were no differences in correlation coefficients between spirometry volumes and EIT volumes obtained using either conventional or textile electrodes.

Alexei Katashev, Alexander Okss, Sabine Krüger-Ziolek, Benjamin Schullcke, Knut Möller

Estimation of Emptying Urinary Bladder in Paraplegic and Elderly People Based on Bioimpedance, Hypogastric Region Temperature and Neural Network

As is known, bioimpedance is a measurement method that can be used in medicine to know the volume of a person’s urinary bladder. However, this method is not entirely reliable due to the multiple factors that influence its measurement, such as the weight of the person, body fat and even the different skin type of each person. Therefore, this paper proposes a method that combines bioimpedance, hypogastric region temperature and an artificial feed-forward neural network, sufficiently capable of determining when to empty the bladder, so that this muscle is not affected by the time exceeded of urine continence, this work is aimed to people who have suffered injuries to their spine, who do not have the ability of feeling when their bladder needs to be emptied. It is also aimed to older adults who begin to have problems with their bladder control, allowing them to improve their quality of life.

Michael Rodas, Layla Amoroso, Mónica Huerta

Research of Impedance Characteristics with a Negative Pressure Breathing Using Rheocardiographic and Rheoencephalographic Signals

Negative pressure breathing is a spontaneous breathing with negative (relative to external, atmospheric) pressure in airways and lungs during the complete respiratory cycle or at certain phase. Our study was aimed at evaluation changes in cardiovascular system caused by applying negative pressure during inspiration (NPBin). Negative pressure was produced by enhanced inspiratory valve in standard valve box connected to mouthpiece. Seven healthy normal male volunteers participated in the study. An age of the volunteers was from 19–34 years, the mean ± SD was 25.7 ± 6.3. The study included five series conducted on the same protocol with each volunteer. Value of applied negative pressure was the only difference between series (0, −10, −15, −20, −25 cm water). Each series was divided into three stages: 15 min before applying NPBin, 25 min of NPBin, 15 min after NPBin. Rheocardiographic and rheoencephalographic signals were recorded continuously during all three stages. A study of an impedance changes was conducted with a negative pressure breathing using rheocardiographic and rheoencephalographic signals. Our study is shown that adaptation period duration to influence of different magnitude at volunteers is not equal. It depends on NPBin level and increases with rising of pressure magnitude.

P. V. Luzhnov, A. I. Dyachenko, Yu. S. Semenov

Comparison of Home Blood Pressure Measurement Devices on Artificial Signals

Cardiovascular diseases are well known as one of the leading causes of death in developed countries. The hypertension is a significant danger and should be monitor carefully. In recent decades, auscultatory and oscillometric methods become as widely used for blood pressure measurement. In clinical practice, blood pressure measuring devices are evaluated according to validating protocols. Despite these protocols, a market with the automatic devices for home self-measurement of the blood pressure is flooded by a lot of cheap devices with doubtful accuracy. The aim of this study is to compare selected devices for the self-measurement in the home conditions. The devices were evaluated using the blood pressure simulators. For each device and each type of blood pressure signal, the absolute and the relative errors of the diastolic and the systolic pressures were evaluated. The obtained results show that the measurement error of these devices could be frequently higher than 5 mmHg and it is necessary to concern with the accuracy of the devices.

Jan Havlík, Markéta Sušánková

Pulsed Transmission Waveform to Mitigate Tissue Thermal Effects in Transcutaneous Wireless Energy Supply Systems for High-Power Rated Medical Implants

Therapeutic options in end stage heart failure include cardiac transplantation or mechanical circulatory support: Left Ventricular Assist Device (LVAD) or Total Artificial Heart (TAH). These devices have relatively high power requirements (5–80 W). Existing power supplies to LVAD and TAH are via percutaneous drivelines with a high frequency of complications including infection. We have developed a wireless Transcutaneous Energy Transmission (TET) waveform protocol and system technology which address the major clinical drawbacks of existing systems: skin tissue thermal effect and system durability. Conventional single-channel TET solutions have significant limitations, including inefficient energy transfer characteristics and high energy density levels producing tissue thermal effects. A reduced lifetime of the internal rechargeable battery is an additional drawback. In the proposed novel system, a multi-channel, time-space multiplexed and pulsed RF transmission waveform transcutaneous power delivery approach, is presented for sustained internal energy supply to high-power rated implantable devices. The bench system prototype performance evaluation results, revealed excellent high-energy transfer efficiency and safer management of lower energy density levels. In conclusion, the proposed pulsed transmission waveform protocol and multi-channel concepts can be configured for individual high-power rated LVAD devices to effectively mitigate tissue thermal effects and to prolong backup battery lifetime.

Omar Escalona, Niall Waterman, James McLaughlin, David McEneaney

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