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About this book

This book gathers the proceedings of the 17th International Conference on Electrical Bioimpedance (ICEBI 2019), held on June 9-14, in Joinville, Santa Catarina, Brazil. The chapters cover the latest knowledge and developments concerning: sensors and instrumentation to measure bioimpendance, bioimpedance imaging techniques, theory and modeling and bioimpendance, as well as cutting-edge clinical applications of bioimpendance. All in all, this book provides graduate students and researchers with an extensive and timely snapshot of current research and challenges in the field of electrical bioimpendance, and a source of inspiration for future research and cross-disciplinary collaborations.

Table of Contents

Frontmatter

Bioinstrumentation

Frontmatter

Design and Integration of Electrical Bio-Impedance Sensing in a Bipolar Forceps for Soft Tissue Identification: A Feasibility Study

This paper presents the integration of electrical bio-impedance sensing technology into a bipolar surgical forceps for soft tissue identification during a robotic assisted procedure. The EBI sensing is done by pressing the forceps on the target tissue with a controlled pressing depth and a controlled jaw opening distance. The impact of these 2 parameters are characterized by finite element simulation. Subsequently, an experiment is conducted with 4 types of ex-vivo tissues including liver, kidney, lung and muscle. The experimental results demonstrate that the proposed EBI sensing method can identify these 4 tissue types with an accuracy higher than 92.82%.

Zhuoqi Cheng, Diego Dall’Alba, Darwin G. Caldwell, Paolo Fiorini, Leonardo S. Mattos

Influence of Measurement Pattern on RAW-data in Electrical Impedance Tomography

The conductivity distribution inside a volume conductor can be reconstructed with Electrical Impedance Tomography (EIT). Therefore, electrodes on the surface of the volume conductor are used to inject a constant current and measure the resulting surface potentials, which is equivalent to transfer impedances. A sequence of current injections and voltage measurements is called measurement pattern and results in a set of transfer impedances. Various measurement patterns exist and each of them has a specific sensitivity, which influences the distinguishability of an object in the reconstructed image. To compare different patterns we introduced three criteria based on the RAW-measurement and evaluated the performance in a water-tank experiment. Measurement patterns with an increased distance between the injecting and measuring electrodes showed more sensitivity and selectivity in the RAW-data and should be preferably chosen compared to the traditional adjacent pattern.

Tobias Menden, Tobias Textor, Samantha Schadwinkel, Steffen Leonhardt, Marian Walter

Hardware Setup for Tetrapolar Bioimpedance Spectroscopy in Bandages

As the demographic change progresses, medical research begins to focus on geriatric diseases. Our work concentrates on patients who suffer from age-related weakness of connective tissues or dilated venous valves which result in chronic venous insufficiency (CVI). CVI leads to a reduced perfusion of limbs, increased venous pressure and tissue deficiency, especially in the lower leg. As a result, chronic wounds develop that can persist for several decades. In clinical practice, CVI patients with wounds are outpatients who consult a physician for diagnosis every two months.A possible way to improve the interval of diagnosis are monitoring technologies like bioimpedance spectroscopy (BIS), which is capable to detect changes in tissue integrity. Developing a device for BIS in bandages could therefore enable quasi-continuous wound status monitoring and alert the physician if necessary. The presented hardware setup for BIS includes textile based electrodes for tetrapolar measurements that can be integrated into a bandage without reducing the comfort of the patient. Shape and size of the electrodes correspond to those of typical wound dressings. The hardware is based on the device AFE4300 for low energy consumption in place of highly dynamic or continuous measurements, as wound status dynamics are slow. We show that the complex impedance of human tissue can be measured with high precision if the electrodes were covered with compression stockings, as contact pressure enhances electrode-skin response.

Stephan Dahlmanns, Alissa Wenzel, Steffen Leonhardt, Daniel Teichmann

Selection of Cole Model Bio-Impedance Parameters for the Estimation of the Ageing Evolution of Apples

Electrical impedance spectroscopy (EIS) is an emerging, fast, reliable and non-destructive technique for fruit quality assessment. In this paper, bio-impedance spectroscopy (BIS) measurements were carried out to monitor apple ageing evolution during a 12 days period using a microcontroller-based system. The data was extracted in the 100 Hz - 85 kHz frequency range and the resulting impedance spectra were fitted with the Cole equivalent circuit. The four variables of the circuit, namely series and parallel resistance ($$R_s$$ and $$R_p$$) and constant phase element (CPE) magnitude and phase, were extracted from the model and evaluated in terms of their correlation with the studied fruit ageing evolution. The results indicated that the parallel resistance ($$R_p$$) decreasing trend is useful to cluster the apples according to the ageing stage, while the CPE parameters allow discriminating among single fruits physiological conditions at the same maturity stage.

Pietro Ibba, Giuseppe Cantarella, Biresaw Demelash Abera, Luisa Petti, Aniello Falco, Paolo Lugli

Biosensor Based on Carbon Nanocomposites for Detecting Glucose Concentration in Water

New materials have been developed with nanotechnology since the 1960s. Carbon-based nanocomposites are used as biosensor due to structural, electrical and thermal properties. These nanocomposites have advantages as high sensitivity, mechanical flexibility, and biocompatibility useful in glucose sensors. Non-conventional methods have been used to measure glucose in physiological fluids like urine, sweat, saliva, breath, interstitial and ocular fluid. This work presents preliminary results of electrical impedance spectroscopy measurements at low glucose concentrations (36–1000 µM). It uses bipolar sensor coated with a mixture of DBEGA and graphene. Results indicate a higher sensitivity (348 Ω/µM) in glucose concentrations lower than 200 µM. The sensitivity diminished with increments of glucose concentration. This sensor has a promising application to quantify glucose concentrations in frequencies between 100 Hz to 10 MHz with low Electrode-Electrolyte Interface. A possible sensor application is monitoring continuously physiological aqueous media as urine, sweat or saliva sensing for hypoglycemic and hyperglycemic patients

John Alexander Gomez-Sanchez, Renata Hack, Sergio Henrique Pezzin, Pedro Bertemes-Filho

Bioimpedance Measurements on Human Neural Stem Cells as a Benchmark for the Development of Smart Mobile Biomedical Applications

Over the past 30 years, stem cell technologies matured from an attractive option to investigate neurodegenerative diseases to a possible paradigm shift in their treatment through the development of cell-based regenerative medicine (CRM). Implantable cell replacement therapies promise to completely restore function of neural structures possibly changing how we currently perceive the onset of these conditions. One of the major clinical hurdles facing the routine implementation of stem cell therapy is the limited and inconsistent benefit observed thus far. While unclear, numerous pre-clinical and a handful of clinical cell fate imaging studies point to poor cell retention and survival. Coupling the need to better understand these mechanisms while providing scalable approaches to monitor these treatments in both pre-clinical and clinical scenarios, we show a proof of concept bioimpedance electronic platform for the Agile development of smart and mobile biomedical applications like neural implants or highly portable monitoring devices.

André B. Cunha, Christin Schuelke, Arto Heiskanen, Afia Asif, Yasmin M. Hassan, Stephan S. Keller, Håvard Kalvøy, Alberto Martínez-Serrano, Jenny Emnéus, Ørjan G. Martinsen

Bioimpedance Theory and Modelling

Frontmatter

Numerical Simulation of Various Electrode Configurations in Impedance Cardiography to Identify Aortic Dissection

Impedance cardiography (ICG) is a non-invasive method to evaluate several cardiodynamic parameters. Pathologic changes in the aorta, like an aortic dissection, will alter the aortic shape as well as the blood flow and, consequently, the impedance cardiogram. This fact distorts the evaluated cardiodynamic parameters on the one hand, and offers the possibility to identify aortic pathologies on the other hand. In order to find an appropriate measurement configuration, in particular for the identification of aortic dissections, a 3D simulation model has been used. Various electrode positions have been investigated to reach a high sensitivity with respect to the discrepancy between the healthy and the dissected case.

Alice Reinbacher-Köstinger, Vahid Badeli, Gian Marco Melito, Christian Magele, Oszkar Bíró

Numerical Simulation of Impedance Cardiogram Changes in Case of Chronic Aortic Dissection

Aortic dissection is an extremely dangerous aortic disease which alters the aortic shape as well as the blood flow in the region concerned. A numerical simulation model based on the Thoracic Electrical Bioimpedance technique for investigating effects caused by the aortic dissections is proposed. The effect of these changes on time-dependent hemodynamic parameters are shown.

Vahid Badeli, Alice Reinbacher-Köstinger, Oszkar Biro, Christian Magele

Analysis of Silicone Additives to Model the Dielectric Properties of Heart Tissue

VADs (Ventricular Assist Devices) support the weakened heart by pumping blood carrying oxygen and life-essential nutrition into the organs. The advantageous location of minimal-invasive catheter-based VADs in the left ventricle and the aorta can be used to determine relevant cardiac parameters to achieve physiological and individual control of the VAD according to the needs of the patient. These parameters can be used to accelerate weaning from the pump, leading to an improvement in the patient’s quality of life. To date, impedance technology is a suitable tool for monitoring the volume of hollow organs and analysing electrical changes in tissue properties. Using this technique in the heart, we believe that cardiac recovery in VAD therapy can be improved by measuring left ventricular volume and myocardial property changes due to insufficient perfusion.In previous work we presented the development of silicone anatomical heart phantoms for impedance measurement in VAD therapy. In this work we introduce different silicone additives to model the electrical properties of heart tissue. Therefore, two additives, carbon and barium titanate, were analysed with an LCR-meter regarding amplitude and phase of impedance between 1 kHz and 100 kHz and compared to pure silicone samples. Additionally, electrical equivalent circuit models of the samples were investigated and a simulation of sample thickness was performed. We found that mixtures of carbon + silicone have resistive properties in contrast to mixtures of silicone + barium titanate which can be modelled by connecting a capacitor parallel to a resistor. The variation of sample thicknesses showed that electrical properties similar to those of heart tissue can be achieved with the presented additives.

Leonie Korn, Simon Lyra, Steffen Leonhardt, Marian Walter

A Short Review of Membrane Models for Cells Electroporation

This article aims to present some bioimpedance models and mathematical solutions used to describe the theoretical process of electroporation in biological cells. Throughout this article three different models are mentioned, with a greater focus on the last two, which are focused on the formation of pores which theoretically influence the conductivity of the membrane.

Jéssica R. da Silva, Raul Guedert, Guilherme B. Pintarelli, Daniela O. H. Suzuki

Body Composition

Frontmatter

Data Views Technology of Bioimpedance Vector Analysis of Human Body Composition

In 1994, A. Piccoli et al. proposed BIVA—an alternative form of BIA data presentation. Standard values of BIVA are usually presented as 75% and 95% tolerance ellipse.Aim of the work: to assess the accuracy of the classical bioimpedance vector analysis for the population of Russia and to develop the option of a two-dimensional representation of the data of bioimpedance analysis of human body composition.Materials and methodsThe present study used data from 1,635,891 patients aged 5 to 85 who underwent bioimpedance research as part of visiting Russian health centers in 2009–2015. The BIVA ellipses for each year of life were constructed, and their congruence with each other and the ellipses from A. Piccoli’s work using the conics by Bernard Desgraupes’ package in an R environment. Animation software was also developed, which, based on raw data, constructed slices of the actual two-dimensional distribution of any selected pairs of bioimpedance human body composition parameters.Results and discussionCalculated according to the Russian data, the BIVA tolerance ellipses differed from those in A. Piccoli’s work.The ellipses of the Russian population had a non-concentric location: the centers of 50%, 75% and 95% tolerance ellipses do not coincide. In many ages, not only the center displacement was detected, but also changes in the angle of inclination of the main axis of 95% and 50% tolerance ellipses. Ellipses for adjacent ages were different too. The slices of the actual two-dimensional distribution had an irregular shape that varied greatly with age, especially for 95% tolerance cloud.ConclusionBIVA ellipses of the Russian population showed a big difference from Piccoli’s. For an adequate assessment and minimization of possible errors, we should use localized reference values for each gender and age. The proposed two-dimensional representations allow us to analyze four pairs of BIA parameters.

Svetlana P. Shchelykalina, Dmitry V. Nikolaev, Vladimir A. Kolesnikov, Kontantin A. Korostylev, Olga A. Starunova

Analysis of Electrical Bioimpedance for the Diagnosis of Sarcopenia and Estimation of Its Prevalence

Sarcopenia in older adults has become a public health problem associated with several adverse health outcomes that lead to high costs of care. This is why an accurate and timely identification of this condition is required, in order to carry out prevention and early intervention to reduce its prevalence. The most important components of sarcopenia are the loss of quantity and quality of skeletal muscle and diagnosis begins with the evaluation of these two dimensions. Whilst in developed countries there are cumbersome and expensive methods to assess the amount of muscle, such as dual energy x-ray absorptiometry (DEXA), magnetic resonance imaging (MRI) and computerized tomography (CT) countries with fewer resources are able to take advantage of less expensive and easy to apply techniques for the diagnosis of sarcopenia, such as the analysis of electrical bioimpedance. In this study, the latter method was used to estimate the amount of muscle mass, in conjunction with the assessment of the grip strength of the hand and the short battery of physical performance, in order to estimate the prevalence of sarcopenia in 210 older adults in Manizales, Colombia. For this, cut-off points obtained from <2 SDs of muscle mass of a young adult population in the same city were used. The results determined a prevalence of 11.4%, a figure that differs from that found in the same population when skeletal mass index (SMI) cutting points obtained from a Taiwanese or a Mexican American population were used (9.5% and 27.6%). On the other hand, the phase angle, another bioimpedanciometric parameter, emerges which could be a promising risk marker for sarcopenia, since the difference in this between individuals with or without sarcopenia was significant (5.79 ± 0.76 vs. 6.26 ± 0.79, p = 0.006°). However, as was shown in the analysis of the ROC curve, its predictive capacity was low in this study and an additional exploration of this topic is required.

Clara Helena Gonzalez-Correa, Maria Camila Pineda-Zuluaga, Luz Elena Sepulveda-Gallego

Sarcopenia in Patients with Chronic Obstructive Pulmonary Disease and Evaluation of Raw Bioelectrical Impedance Analysis Data

Chronic Obstructive Pulmonary disease (COPD) is associated with extrapulmonary comorbidities related to alterations in the amount and function of muscle mass, such as sarcopenia. However, there is a paucity of studies that use the diagnostic criteria for sarcopenia proposed by the European Working Group on Sarcopenia in the Elderly (EWGSOP, is the acronym in English) in this condition. This group has supported the use of Bioelectrical Impedance Analysis (BIA) as a technique to estimate muscle mass. On the other hand, some authors have suggested that raw BIA data such as the impedance ratio (IR) 250 kHz/5 kHz and the phase angle (PA) obtained from this technique could be indicators of sarcopenia. Few studies have explored the use of these variables in patients with COPD. The aim of this study was to evaluate the presence of sarcopenia in these patients according to the EWGSOP criteria and to compare the IR and PA in patients with and without sarcopenia. The results showed that 50% of the patients were diagnosed with sarcopenia. This condition was related to the degrees of severity of COPD. IR and PA were not different in patients with COPD with and without sarcopenia. BIA is a useful tool for the comprehensive evaluation of COPD patients, however, the IR and PA variables in this study were not indicators of sarcopenia in these patients.

Maria Camila Pineda-Zuluaga, Clara Helena Gonzalez-Correa, Luz Elena Sepulveda-Gallego

Skeletal Muscle Index Using Bioelectrical Impedance for Diagnosis of Sarcopenia in Two Colombian Studies

Sarcopenia is defined as a loss of muscle mass depending on ageing and affecting physical function. The objective of this study was to assess the performance of the new cut-off points for SMI in another similar population and to evaluate if both cut-off points classify the muscle mass of the individuals in the same category. Methods: forty-five men aged 22.6 ± 3.2 years were included. Percentage body fat (%BF) was estimated by four skin folds, skeletal mass index (SMI) by BIA, and muscle function by the handgrip strength test (HGS). Results: Cut-off points generated with the new population were similar to those found in the previous study. With both cut-off points, none of our young patients showed low muscle mass estimated by SMI. Discussion and Conclusion: Individuals were classified in the same category with both cut-off points. However, it is recommended, in a future study, to establish whether these data coincide with those obtained directly from a population of elderly people in the same city using BIA in contrast to another technique of reference such as DXA.

Clara Helena Gonzalez-Correa, Julio Cesar Caicedo-Eraso, Diana Rocío Varon-Serna

Clinical Applications on Bioimpedance

Frontmatter

Bioimpedance Measurement to Evaluate Swallowing in a Patient with Amyotrophic Lateral Sclerosis

Objective: Swallowing dysfunction is an increasingly common symptom in the patients with amyotrophic lateral sclerosis (ALS). The traditional videoflouroscopy method allows observation of the entire oropharyngeal swallowing process during the examination; however, it is expensive and requires the use of ionizing radiation. Impedance pharyngography (IPG) is a new cost-effective and non-invasive method for real-time swallowing monitoring. The goal of the present pilot study is to investigate whether IPG could be used for evaluating the swallowing process in ALS patients and to learn how IPG waveforms relate with videoflouroscopy data. Method: A new IPG measurement system based on a lock-in amplifier was developed, which can be used for acquiring both the impedance magnitude and phase of the IPG signal, rather than impedance magnitude-only information as is typically done today. Results: Physiological significance of the obtained IPG waveform was confirmed by comparing the chronological series of anatomical events recorded simultaneously with the videoflouroscopy swallowing exam. Significance: IPG may be used as a simple clinical tool for estimating swallowing function of ALS patients with minimal stress and inconvenience.

Fu Zhang, Courtney McIlduff, Hilda Gutierrez, Sarah MacKenzie, Seward Rutkove

Three Electrode Arrangements for the Use of Contralateral Body Segments as Controls for Electrical Bio-Impedance Measurements in Three Medical Conditions

Some medical and physiological conditions like diabetic foot ulcers (DFU), fractures, skin cancer, as well as higher physical lateral development of one side of the body in sports like soccer, have an unilateral presentation and frequently in one of the limbs. Electrical bio-impedance (EBI) can be useful in the diagnosis or follow up of some of these conditions and, in some cases, the unaffected extremity could serve as a control. Nevertheless, functional laterality can affect symmetry and this fact has to be taken into consideration. Four different approaches for EBI measurements are proposed in order to apply them in the above-mentioned conditions: whole body (WB), large segments (LS), small segments (SS) and a rosette array (RS). WB and LS may be useful for the assessment of soccer players as well as DFU; SS is meant to be applied to the study of fractures and, finally, the RS array can be helpful in the study of skin lesions and the risk of developing DFU. These different arrangements are presented with a nomenclature to be used with each of them. In this particular case, all measurements show lateral asymmetry, values being higher on the left side for WB, LS and SS, while the opposite applies for the majority of the RS readings. All comparisons between both sides show that the differences in LS and SS measurements are statistically significant (P value <<0.05 for WB), as well as for the RS measurements. However, in the latter case, for one group of readings, the P value was just 0.0490.

C. A. Gonzalez-Correa, L. O. Tapasco-Tapasco, S. Salazar-Gomez

Luminal Electrical Resistivity at 50 kHz of the Pig Large Intestinal Wall

In GruBIE we are interested in finding the best conditions to, in the future, carry out in vivo transendoscopic measurements on the colon wall in humans. Pressure applied by the probe to the tissue being measured and probe/electrodes size, as well as thickness of the large intestine (LI) wall may well play a crucial role in the values obtained when readings to the studied tissue are made. In this article, in resected colon specimens from 3 adult pigs, two different approaches are explored, with a probe previously used for in vitro and in vivo measurements in humans and other animals as pigs and rabbits. These two approaches differ, basically, on probe position (tip upside down or tip upside up), with high pressure being applied in the first case (about 27.5 kPa) and low pressure in the second case (about 1.8 kPa for the pieces of colon and about 7.2 kPa for measurements on the rectum). The main finding of this initial study is that both aspects, pressure applied with the tip of the probe and thickness of the tissue, seem to affect the impedance readings. For future work, these two aspects have to be considered and this should be reflected in the probe and electrode sizes.

C. A. Gonzalez-Correa, L. O. Tapasco-Tapasco, S. Ballesteros-Lopez

Evaluating the Effects of Cold Storage on Vascular Grafts Using Bioimpedance Measurement Techniques

The most common vascular preservation method for cardiovascular and transplantation surgeries is cold storage where the vessels are cooled down and kept in a preservation solution till the surgery can be performed. The process of cooling and storage of the vascular tissue affects the quality of the graft. The currently used methods for evaluating the quality of the vascular grafts which are cold stored are destructive and invasive and require segmenting and staining. Bioimpedance measurement technique is a non-destructive method, and the objective of this work was therefore to study how changes in the structure and morphology of the grafts during the cold storage period affect bioimpedance measurements. Bioimpedance measurement technique was employed as a non invasive method to study and evaluate the changes in the quality of ovine jugular veins and carotid artery during 30 days of cold storage in UW solution. The results of the study show that bioimpedance measurement technique can be used for non-invasive and non-destructive monitoring of the quality of the blood vessels during the cold storage period.

Maryam Amini, Jonny Hisdal, Antonio Rosales, Håvard Kalvøy, Ørjan Grøttem Martinsen

Tissue Impedance Spectroscopy to Guide Resection of Brain Tumours

Visual differentiation of lower grade glioma tissue from normal brain tissue during surgery is difficult even for expert neurosurgeons. Therefore, during tumour removal neurosurgeons rely on image guidance. It has been proven that higher rates of tumour resection prolong long-term survival of patients. We aim to implement impedance spectroscopy as a potential supportive tool to improve radical resection. During this pilot study, we evaluated the possibility to differentiate ex vivo tissue samples (biopsy samples during tumour surgeries) with the help of impedance spectroscopy. Tissues were collected from two patients and impedance spectra differences were found between low-grade glioma, high-grade glioma and healthy brain tissue.

Mareike Apelt, Gesar Ugen, Levin Häni, Andreas Raabe, Juan Ansó, Kathleen Seidel

Electrical Impedance Spectroscopy

Frontmatter

Relationships Between Bioimpedance Variables and Gene Expression in Lactuca Sativa Exposed to Cold Weather

Four sets of 4 week-old Lactuca Sativa plants, each with 30 samples, were subjected to a nocturnal frost simulation by inserting them into an instrumented freezer with internal temperature maintained at a constant value of −2 °C. At time points of 60, 120, 180, 240 min, one after another lettuce sets were removed from the freezer to be tested with an electrical impedance spectroscopy device, built in the laboratory and based on a commercial electronic board in which a cut leaf of each plant was subjected to a 1 to 300 kHz frequency sweep of an alternate current with a constant tension of 1 V. Results showed a progressive and statistically significant reduction of the critical frequency for which the phase angle reached its minimum as the frost time proceeded (−40% after 180 min, P < 0.05), and this was interpreted as the well known tissue damage due to ice crystals occurring both in cytoplasm and extra-cellular fluids. A quadratic regression of the critical frequency versus the concentration of the protein LBD1 has also been found, which was over expressed by the cluster of genes, whose primers are AGCA GAGGTGGTGAATTTGC (LACTLBD1-F) and AGCTGCCTAAATTGGC GTTA (LactLBD1-R), identified as markers of the applied cold stress in the lettuce plants. It was concluded that an easy to use and inexpensive electrical impedance spectroscopy device can give strategic information concerning the damage occurring depending on abiotic/cold weather in the field lettuce.

Diego Albani, Alberto Concu, Lara Perrota, Antonio H. Dell’Osa, Andrea Fois, Andrea Loviseli, Fernanda Velluzi

Effect of Heating on Dielectric Properties of Hungarian Acacia Honeys

The statement of overheating of honey during the processing is very important in quality characterization of honey products. Four various Hungarian acacia honeys from different places were hold in water bath of 35, 40, 50, 60, and 80 °C 0,5, 4 and 24 h. After heating the honeys were cooled down to room temperature. The electrical impedance spectrum of honeys before and after heating were measured by precision LCR meters in frequency range from 30 Hz up to 30 MHz at 1 V voltage with Ag/AgCl electrodes at room temperature (22 °C). The measured impedance spectra after open and short correction were approached with a model consisting of a distributed circuit element in serial connection with a resistance. The parameters of this model were determined. The resistance of the distributed circuit element was decreased after heat treatment for all honeys. After more detailed investigation this parameter can be used for detecting the earlier heating of honey products.

Eszter Vozáry, Zsanett Bodor, Kinga Ignácz, Bíborka Gillay, Zoltán Kovács

Impedance Measurements Sensitive to Complementary DNA Concentrations

Developing countries have obstacles reaching quality and innovative healthcare services since there is limited access to the new technologies. Such is the case for genetic medicine, where the Deoxyribonucleic Acid (DNA) detection techniques are complex and expensive. In recent years, the development of genosensors has been of great interest, since it offers cheaper alternatives for specific DNA detection. In this work, we explored the use of multifrequency impedance measurements to detect three concentrations of DNA without labeling. The results suggest that impedance could be useful as a concentration sensitive DNA measurement parameter and then be used for the development of easy-to-use and potentially cheaper technologies.

Gerardo Ames, R. Gnaim, J. Sheviryov, A. Goldberg, M. Oziel, E. Sacristán, César Antonio González

Monitoring Lactobacillus Bulgaricus Growth in Yoghurt by Electrical Impedance

Characterization of different Lactobacillus bacterial strains has an increasing demand due to their potential health benefits. Classical cell counting methods are time-consuming and require well trained laboratory work, besides they are having higher subjectivity and error. The determination of electrical impedance spectrum is a promising method for the evaluation of changes in chemical structure and cell growth during the formation of yoghurt. Our aim is to use electrical impedance spectrum for the monitoring of cell growth of LABs. In this study different strains of Lactobacillus bulgaricus bacteria were used for the production of yoghurt from ultrahigh temperature processed (UHT) milk of 1.5% fat content. The cell count of the LABs was determined with plating method on MRS (De Man, Rogosa and Sharpe) agar in each hour during 12 h of cultivation at 37 °C. For impedance measurements, the real part (conductance) and the imaginary part (susceptance) of admittance (reciprocal value of electrical impedance) were recorded through 12 h at 37 °C in frequency range from 50 Hz up to 800 kHz with a HP 4284A precision LCR meter. Results showed a bacteria cell number increase from magnitude 103 to 107 (CFU/milliliters) as with conductance and the susceptance. Regression models could also accurately predict bacterial cell count. Impedance measurement during the formation of yoghurt can be useful in monitoring Lactobacillus growth and determination of cell number, when exact methodologies and setups are applied.

Zsanett Bodor, John-Lewis Zinia Zaukuu, Tímea Kaszab, Anikó Lambert-Meretei, Mahmoud Said Rashed, Zoltan Kovacs, Csilla Mohácsi Farkas, Eszter Vozáry

Electrical Impedance Tomography

Frontmatter

Source Consistency Frequency Difference Electrical Impedance Tomography (sc-fdEIT)

Based on the frequency spectroscopy of the biological tissues given by BIS, we aim to separately reconstruct the different frequency-dependent sources using the newly proposed image reconstruction technique called source consistency frequency difference electrical impedance tomography (sc-fdEIT). The boundary frequency-dependent voltages can be approximated in first or second order with respect to the frequency-dependent spectroscopy of each separated sources which is prior information in this study. The numerical simulation results show the feasibility of the proposed sc-fdEIT method as a new noninvasive technique for the identification of the frequency dependent object mixed in the domain.

Tingting Zhang, Tong In Oh, Eung Je Woo

A Measure of Prior Information of a Pathology in an EIT Anatomical Atlas

One approach to solve the Electric Impedance Tomography inverse problem is the Bayesian Inference. The use of Bayes’ Rule of conditional posterior probability density functions requires the definition of two probability density functions, a prior probability density function and a likelihood. The prior probability density function is often called Anatomical Atlas when the information is based on anatomy and physiology. Sufficient prior information of a pathology is necessary in order to have this pathology correctly represented in the tomographic image. A measure of how much a particular pathology is represented in an anatomical atlas is proposed.

Rafael Mikio Nakanishi, Talles Batista Rattis Santos, Marcelo Britto Passos Amato, Raul G. Lima

Functional Segmentation for Electrical Impedance Tomography May Bias the Estimated Center of Ventilation

Functional segmentation of the region of interest (ROI) on electrical impedance tomography (EIT) images is performed by exclusion of voxels with volume variation below a specified threshold. Considering the heterogeneous spatial distribution of poorly aerated regions, this work assessed the ROI threshold influence on the ventilation distribution of healthy lungs. Sixteen adults were mechanically ventilated and positive end-expiratory pressure (PEEP) titrated (20 to 4 cmH2O with 2 cmH2O steps, 100 s each) while ventilatory and EIT data were recorded. ROI were delimited for each PEEP step based on the respective step (ROISTEP) or the maximum PEEP (ROIMAX PEEP), and on thresholds of 5%, 10%, 15% and 20%. Spatial distribution of ventilation was assessed by the center of ventilation (CoV) and the difference between higher thresholds (10%, 15% and 20%) and their respective 5% threshold counterpart (dCoV). Results showed positive correlation between CoV and PEEP for all strategies. While dCoV was not significantly different from zero for ROIMAX PEEP, ROISTEP dCoV was inversely proportional to PEEP and directly proportional to the chosen threshold. These results suggest that assessments of spatial distribution of ventilation might be biased by functional ROI delimitation parameters, especially for lower PEEP values.

Alcendino Jardim-Neto, Juliana Neves Chaves

Preliminary Results of a Clinical EIM System

This paper presents the results of the first case of volunteer experiment for a clinical trial that carried out in early 2019 for an Electrical Mammography (EIM) system. The EIM system is designed to detect human breast cancer and distinguish between different cancerous tissues in-vivo. Before volunteer trial there were vegetable experiments and positive results of extracting Cole-Cole parameters [1] using multiple-frequencies imaging method are obtained. In this paper, two volunteers who were diagnosed with malignant tissue in one breast was participated in a trial. We can see abnormality in reconstructed images that indicating differences between left and right breast. The position of the abnormal object was found to be in the same position of X-ray mammogram diagnosis as well as clinical pathological examination report. The system is going to acquire more volunteer data before going into clinical trial.

Wei Wang, Gerald Sze, Zhao Song

Non-linear Bioimpedance Phenomena

Frontmatter

Computational Study of Parameters of Needle Electrodes for Electrochemotherapy

Electroporation is a phenomenon that increases cells permeability due to applications of electric fields. Electrochemotherapy uses electroporation to facilitate drugs insertion into tumor cells. Guarantee that all tumor tissue will be electroporated is vital to treatment success. Needle electrodes can present complex electric field distribution. This paper aims to study electric field changes due to variations in electrodes and application protocols parameters. Besides, we suggest a superposition approach to improve electroporation treatment.

Jéssica R. da Silva, Raul Guedert, Guilherme B. Pintarelli, Daniela O. H. Suzuki

Other Bioimpedance Application

Frontmatter

Bone Fracture Detection by Electrical Bioimpedance: Measurements in Ex-Vivo Mammalian Femur

To simulate a limb, two phantoms of bovine femurs (one with an intact bone and the other with a bone sawn in two) were constructed and non-invasive Electrical Impedance Spectroscopy measurements were taken on them in order to identify differences in their respective Cole Cole diagrams. Impedance spectroscopy was performed by a frequency sweep between 1 Hz and 65 kHz at a fixed current of 1 mA. The results obtained show wide differences in the Cole Cole diagrams of both phantoms (intact and fractured bone), especially concerning the real component of the impedance, which was always lower in the fractured femur than the whole one around the bones’ section corresponding to that of the lesion in both femurs. These superficial (non-invasive) measurements correspond to the base measurements of electrical impedance spectroscopy and they could, in turn, correspond to what occurs in mammals immediately after a fracture occurs, i.e. a dramatic increase in electrical conductivity due to the diffusion into the fracture site of more conductive materials such as the blood and the extravascular fluids.

Antonio H. Dell’Osa, Alberto Concu, Fernando Dobarro, J. Carmelo Felice

Bioimpedance Technology for Assessing Blood Filling Redistribution in Human Body Regions During Rotation on Short Radius Centrifuge

Space microgravity lead to changes in the functioning of most human organs and systems, including cardiovascular. Installation of a complex with a gravitational training effect (for example, a short-radius centrifuge (SRC)) on board a spacecraft may be a solution to this problem.Aim of the work: to assess the possibilities of the polysegment bioimpedance method for monitoring the blood filling redistribution in body regions during rotation on a SRC.Materials and methodsNine healthy male volunteers aged 25–40 years participated in three SRC rotation modes (twice 60 and once 45 min). Each mode on the SRC consisted of three phases with uniform acceleration up to values of 0.2 g, 1.05 g and 2 g/2.4 g/2.9 g and of three phases with uniform deceleration. The relative change in resistance at a probing current frequency of 5 kHz was assessed using the bioimpedance analyzer in the polysegment mode.Results and discussion21 complete records were registered, and 4 records were incomplete, i.e. the study was terminated for medical reasons. The electrical resistance of the head and thorax regions during the SRC rotation maximally increased by +16% and +23%, indicating a decrease in blood filling, while the electrical resistance of the leg regions decreased by –17%.The blood outflow from the head and the flow to the legs did not depend on the SRC rotation mode during first 30 min, and was expressed in average changes by +10% in the head and −15% in the legs.ConclusionThe method is good for recording the fluid redistribution during rotation on a SRC and can later serve as an instrumental basis for diagnosing and predicting syncopal states.

Svetlana P. Shchelykalina, Milena I. Koloteva, Yulia V. Takhtobina, Yuri I. Smirnov, Alexander V. Smirnov, Galina Yu. Vassilieva, Dmitry V. Nikolaev

Differences in the Electrical Impedance Spectroscopy Variables Between Right and Left Forearms in Healthy People: A Non Invasive Method to Easy Monitoring Structural Changes in Human Limbs?

The resistive component of bioimpedance was non invasively assessed in both right and left upper arms of 11 healthy female and 9 male subjects (28.4 ± 1.4 years; 63.8 ± 11.8 kg; 167.4 ± 7.5 cm) all of whom were right-handed. A homemade electrical impedance spectroscopy device which implemented the AD 5933 electronic board was utilized, and the bipolar modality of bioimpedance assessment was chosen using two disposable ECG surface electrodes placed at each end of the biceps brachial muscles while subjects were sitting comfortably. Upper arm resistance was acquired at sweeping frequency steps of 15, 30, 45, 60 and 75 kHz. Results showed a significantly lower mean value of resistance in right versus left upper arms: −27.4 Ω, P < 0.05 or about −4%, at the frequency of 15 kHz. It was concluded that some errors of data interpretation may occur in the case of lymphedema in one arm and thus, electrical impedance spectroscopy was utilized to monitor the water volume trend in that arm in comparison with the other arm. These results underline a predominantly low value of the resistance in the main upper arm compared to that in the auxiliary one, even in healthy subjects. Therefore, care must be taken when the electrical impedance spectroscopy is adopted in these clinical assessments.

A. H. Dell’Osa, A. Concu, M. Gel, A. Fois, Q. Mela, A. Capone, G. Marongiu, A. Loviselli, F. Velluzzi

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