Electromagnetic Actuation and Sensing in Medical Robotics

With the advancement in robotics technology, medical field is evolving more with minimally invasive to noninvasive procedures. Minimally invasive surgical procedures have gained ever-increasing popularity over the past decades due to many of their advantages compared to traditional open operations, such as smaller incisions, faster recoveries, fewer complications, and shorter hospital stays. Robot-assisted minimally invasive surgery promises to improve the precision, dexterity, and stability of delicate procedures. Among these technologies, there is a demanding clinical need to progress the field of medical robotics in connection with noninvasive surgery. For this, the actuation and sensing in the future robotic surgery systems would be desired to be more wireless/untethered. Out of many promising wireless actuation and sensing technologies, one of the most patient friendly techniques to use is electromagnetic or magnetic actuation and sensing for feedback control and manipulation. In this book, we have intended to elucidate the recent related research and developments behind the electromagnetic actuation and sensing implemented in medical robotics and therein.

Advantages of flexible polymer materials with developments in refined magnetic actuation can be intertwined for a promising platform to work on a resilient, adaptable manipulator aimed at a range of biomedical applications. Moreover, soft magnetic material has an inherent property of high remanence like the permanent magnets which can be further refined to meet ever-increasing demands in untethered and safe-regulated medical environments. In this chapter, we focus mostly on different avenues and facets of flexible polymer materials in adaptable actuation and sensing in the context of magnetic field for range of biomedical applications.

This chapter covers the design principles of magnetic actuated catheter robot and is outlined as follows. Section 1 discusses key fundamental principles to design for an electromagnetic catheter/guide wire type surgical robot. The clinical perspectives are covered in Sect. 1.1 and in Sect. 1.2 the overarching electromagnetic theory is mentioned. Electromagnetic systems can be further decomposed into the stators (stationary wound coils) and actuators (moving part usually consists of permanent magnet), where the stators can be interpreted as the input and the actuator the output. Section 2 will cover the design consideration of stators and Sect. 4 the design principles of the actuators. Sections 2 and 3, aim to provide the reader with an intuitive approach to designing their own electromagnetic system. Section 3 will further exemplify principles covered in Sects. 2 and 3 with a fabricated prototype from our lab. These electromagnetic catheter systems can be classified by many parameters; one important parameter is the bending angle and will be addressed in Sect. 4. The use of this angle is demonstrated for a surgical context. This chapter concludes in Sect. 8, providing an overview of the works presented and the future directions.

The introduction of surgical robots improves the quality of healthcare due to the minimal invasiveness, reduced pain of patients, improved efficiency, accuracy, and the efficacy of surgery. The majority of the existing surgical robotic systems are based on master–slave teleoperation mode. The emerging handheld collaborative control modes in robotic systems omit the teleoperation master, and instead use handheld intelligent controls to directly drive its actuator end in order to eliminate motion control uncertainties such as tremors. This chapter puts forward a novel kind of handheld robot system driven by magnetic actuators based on the magnetically suspended technology. The configuration analysis and the design method of magnetic bearing with current bias are presented, and then the analysis and method of the 1-DOF (Degree of Freedom), 3-DOF, and 4-DOF magnetic suspension-based robotic actuator systems are proposed in details.

Biomedical robotic applications with accuracy requirements demand real-time position and orientation tracking, such as in the field of human motion tracking, rehabilitation, surgical instrument tracking, among many others. Among the state-of-the-art tracking technology, magnetic sensing method is an effective technology to provide fast and accurate tracking result without suffering from occlusion drawbacks. Magnetic sensing techniques are used to sense the distribution of a magnetic source field. With the sensing signals, the pose (position and orientation) between the sensor(s) and the source(s) can be estimated according to the magnetic field distribution model. In contrast to other optical tracking technologies in the clinical setup, magnetic sensing has no line-of-sight problem and is easy to be embedded with many instruments. Therefore, it is useful in intracorporeal applications to provide the location information of the tracked targets inside the human body. For this reason, magnetic sensing techniques have potential to further improve the applications of computer assisted surgeries. For example, flexible curvilinear manipulators or endoscopic devices nowadays need to be tracked in real time for better and safer operations. This chapter gives an overview of how the magnetic sensing technology works in the field of medical instrument tracking. After that, the sensing applications will be given in detail. Three typical medical applications will be discussed: (1) magnetic sensing for wireless capsule robots; (2) Current magnetic sensing devices in clinic setups; and (3) magnetic sensing for flexible surgical robots.

In the past decade, with continual advancement in the magnetic field sensing technology, passive magnetic tracking has become an emerging trend in the field of medical intervention. By embedding a small permanent magnet in the medical instrument, the passive magnetic tracking approach makes the system possible to have untethered, compact and wearable, even modular design for better ergonomics and lower hardware requirements. In this chapter, an overview of the working principle and methods of the passive magnetic tracking technology was presented. Implementation of the technology in actual medical interventions were also demonstrated. Lastly, the challenges in the development of this technology were explored and discussed.

In this chapter, motion of magnetic particles were captured using ultrasound imaging with contrast-enhanced microbubbles. Ultrasound videos were captured and analyzed by the created tracking algorithm to determine the efficiency and accuracy of the algorithm. It is necessary to ensure an efficient and accurate tracking method of the particles in order to evaluate future in vitro or in vivo applications of the microbubbles, when implanted into an enclosed system and imaged using ultrasound. First, it was found that the porous structure of the magnetic microbubbles could be successfully fabricated based on a gas foaming technique, using alginate (low viscosity, 2% (w/v)) as the polymer, mixed homogeneously with sodium carbonate (4%) solution. The reaction between sodium bicarbonate and hydrogen peroxide (32 wt %) in the collecting solution allowed the creation of encapsulated microbubbles. The alginate went under crosslinking in the collecting calcium chloride (25% w/v) solution. Second, it was proven that the encapsulated microbubbles enhanced the resultant ultrasound images, with the air bubbles appearing as bright white spots. In contrast, the solid spheres appeared dull and at times could not be seen under ultrasound. The contrast enhancing properties of the microbubbles allowed the microbubbles to be detected by the tracking algorithm, as compared to the solid spheres which could not be detected at all. Third, ground truth of the (x, y) coordinates of the microbubble centroids were determined using manual selection by the user mouse. Based on the accuracy analysis done, the accuracy of the tracking algorithm was 3.33 pixels, or 0.0354 cm, between the algorithm detected and the manually selected (x, y) coordinates of the centroids. Also, the optimal number of particles to be tracked was up to five particles with an accuracy studies.