Over the past six decades there has been tremendous progress made in the field of medical implant communications. A comprehensive review of the progress, current state-of-the-art and future direction is presented in this chapter. Implanted Medical Devices (IMDs) are designed mainly for the purpose of diagnostic, therapeutic and assitive applications in heathcare, active living and sports technology. The primary target of implanted medical devices (IMDs) design revolve around reliable communications, sustainable power sources, high degree of miniaturisation while maintaining bio-compatibility to surrounding tissues adhering to the human safety limits set by appropriate guidelines. The role of internet of things (IoT) and intelligent data analysis in implant device networks as future research is presented. Lastly, in addition to reviewing the state-of-the art, a novel intuitive lower bound on implant size is presented.

This paper, for the first time, fully characterizes the human body as a monopole antenna in the frequency range of 10-110 MHz, which contains the resonance frequency of the human body. The human body is represented by an equivalent cylindrical monopole antenna grounded on a highly conductive ground plane that is analyzed based on the three-term approximation method. The reflection coefficient is measured using a human subject as a monopole antenna. Measurement results show that the theoretical predictions are in reasonable agreement. It is found that the human body resonates between 40 and 60 MHz depending on the posture of the body when it is fed by a 50-Ω impedance system at the base of the foot. A minimum reflection coefficient of -12 dB is measured which demonstrates that the human body can be potentially used as an antenna. Theoretically, it is predicted that the human body can be an efficient antenna with a maximum radiation efficiency reaching up to 70%, which is supported by measurement results found in the literature.

Human body communication (HBC) is a promising wireless technology that uses the human body as part of the communication channel. HBC operates in the near-field of the high frequency (HF) band and in the lower frequencies of the very high frequency (VHF) band, where the electromagnetic field has the tendency to be confined inside the human body. Electromagnetic interference poses a serious reliability issue in HBC; consequently, it has been given increasing attention in regard to adapting techniques to curtail its degrading effect. Nevertheless, there is a gap in knowledge on the mechanism of HBC interference that is prompted when the human body is exposed to electromagnetic fields as well as the effect of the human body as an antenna on HBC. This paper narrows the gap by introducing the mechanisms of HBC interference caused by electromagnetic field exposure of human body. We derived analytic expressions for induced total axial current in the body and associated fields in the vicinity of the body when an imperfectly conducting cylindrical antenna model of the human body is illuminated by a vertically polarized plane wave within the 1-200 MHz frequency range. Also, fields in the vicinity of the human body model from an on-body HBC transmitter are calculated. Furthermore, conducted electromagnetic interference on externally embedded HBC receivers is also addressed. The results show that the maximum HBC gain near 50 MHz is due to whole-body resonance, and the maximum at 80 MHz is due to the resonance of the arm. Similarly, the results also suggest that the magnitude of induced axial current in the body due to electromagnetic field exposure of human body is higher near 50 MHz.

Health-care monitoring and diagnostics technology continues to be of great interest in research due to an increasing trend in the number of people with chronic diseases. To improve accuracy and timeliness of diagnosis, electronic devices could be implanted inside human body to provide various real-time diagnostic information. However, effective technique for communicating the implant with outside world is still an open problem. Early efforts based on radio wave propagation are standardized as the medical implant communication services (MICSs) for 402-405-MHz frequency range, which was later adopted as medical device radiocommunication services for 401-406-MHz frequency range. Intrabody communication (IBC) is a relatively new technique that uses the human body as a channel with communication frequencies not exceeding several megahertz. In this paper, we propose a new analytical electromagnetic model that uses galvanically coupled IBC as an alternative to radio wave-based implant communication. The model is unified in the sense that it is based on multilayered ellipsoidal geometry that can be applied to any part of the body (i.e., head, torso, limbs, and so on). Our model effectively describes the influences of tissue layer thicknesses and electromagnetic properties, implant size and depth, and geometry of the body part. The model proves the security and low power consumption of IBC. The path loss characterization of IBC implants shows lower values compared with their MICS counterparts.

Currently, the radio-frequency (RF) implant wireless communication is enabled by utilizing small antennas that radiate radio waves inside the human body. As an alternative technique for implant wireless communication, we propose to use the human body itself as an antenna by feeding an RF current into the tissues. In particular, this paper studies the scenario when the RF current is fed by a tiny toriodal inductor that is implanted and clamped around the tissues in the ankle. The frequency range of 1-70 MHz is considered, which includes the resonance frequency of the human body. Theoretical results, from applying small toroidal inductors, show that the system exhibits broadband characteristics with a maximum gain of -25dB between 20 and 40 MHz, assuming an isotropic radiation from human body. However, for the case of the small toroidal inductors considered, the radiation resistance of the system is very small, which increases the power consumption. It is known that the radiation resistance can be further improved by choosing a magnetic core with high permeability and low loss, as well as, by optimizing the number of turns to reduce the parasitic capacitance and obtain a usable magnetizing inductance.

Purpose: This study aimed to develop a low-cost real-time biofeedback system to assist with rehabilitation for patients following total knee replacement (TKR) and to assess its feasibility of use in a post-TKR patient case study design with a comparison group. Method: The biofeedback system consisted of Microsoft Kinect^TM and Nintendo Wii balance board with a dedicated software. A six-week inpatient rehabilitation program was augmented by biofeedback and tested in a single patient following TKR. Three patients underwent a six weeks standard rehabilitation with no biofeedback and served as a control group. Gait, function and pain were assessed and compared before and after the rehabilitation. Results: The biofeedback software incorporated real time visual feedback to correct limb alignment, movement pattern and weight distribution. Improvements in pain, function and quality of life were observed in both groups. The strong improvement in the knee moment pattern demonstrated in the case study indicates feasibility of the biofeedback-augmented intervention. Conclusion: This novel biofeedback software has used simple commercially accessible equipment that can be feasibly incorporated to augment a post-TKR rehabilitation program. Our preliminary results indicate the potential of this biofeedback-assisted rehabilitation to improve knee function during gait. Research is required to test this hypothesis.