Characterization of path loss and absorption for a wireless radio frequency link between an in-body endoscopy capsule and a receiver outside the body

Physical-layer characterization is important for design of in-to-out body communication for wireless body area networks (WBANs). This paper numerically investigates the path loss and absorption of an in-to-out body radio frequency (RF) wireless link between an endoscopy capsule and a receiver outside the body using a 3D electromagnetic solver. A spiral antenna in the endoscopy capsule is tuned to operate in the Medical Implant Communication Service (MICS) band at 402 MHz, accounting for the properties of the human body. The influence of misalignment, rotation of the capsule, and three different human models are investigated. Semi-empirical path loss models for various homogeneous tissues and 3D realistic human body models are provided for manufacturers to evaluate the performance of in-body to out-body WBAN systems. The specific absorption rate (SAR) in homogeneous and heterogeneous body models is characterized and compliance is investigated

Improved reception of in-body signals by means of a wearable multi-antenna system

High data-rate wireless communication for in-body human implants is mainly performed in the 402-405 MHz Medical Implant Communication System band and the 2.45 GHz Industrial, Scientific and Medical band. The latter band offers larger bandwidth, enabling high-resolution live video transmission. Although in-body signal attenuation is larger, at least 29 dB more power may be transmitted in this band and the antenna efficiency for compact antennas at 2.45 GHz is also up to 10 times higher. Moreover, at the receive side, one can exploit the large surface provided by a garment by deploying multiple compact highly efficient wearable antennas, capturing the signals transmitted by the implant directly at the body surface, yielding stronger signals and reducing interference. In this paper, we implement a reliable 3.5 Mbps wearable textile multi-antenna system suitable for integration into a jacket worn by a patient, and evaluate its potential to improve the In-to-Out Body wireless link reliability by means of spatial receive diversity in a standardized measurement setup. We derive the optimal distribution and the minimum number of on-body antennas required to ensure signal levels that are large enough for real-time wireless endoscopy-capsule applications, at varying positions and orientations of the implant in the human body

Applications of Wireless Power Transfer in Medicine : State-of-the-Art Reviews

Magnetic resonance within the field of wireless power transfer has seen an increase in popularity over the past decades. This rise can be attributed to the technological advances of electronics and the increased efficiency of popular battery technologies. The same principles of electromagnetic theory can be applied to the medical field. Several medical devices intended for use inside the body use batteries and electrical circuits that could be powered wirelessly. Other medical devices limit the mobility or make patients uncomfortable while in use. The fundamental theory of electromagnetics can improve the field by solving some of these problems. This survey paper summarizes the recent uses and discoveries of wireless power in the medical field. A comprehensive search for papers was conducted using engineering search engines and included papers from related conferences. During the initial search, 247 papers were found then non-relevant papers were eliminated to leave only suitable material. Seventeen relevant journal papers and/or conference papers were found, then separated into defined categories: Implants, Pumps, Ultrasound Imaging, and Gastrointestinal (GI) Endoscopy. The approach and methods for each paper were analyzed and compared yielding a comprehensive review of these state of the art technologies

Conformal antenna-based wireless telemetry system for capsule endoscopy

Capsule endoscopy for imaging the gastrointestinal tract is an innovative tool for carrying out medical diagnosis and therapy. Additional modalities beyond optical imaging would enhance current capabilities at the expense of denser integration, due to the limited space available within the capsule. We therefore need new designs and technologies to increase the smartness of the capsules for a given volume. This thesis presents the design, manufacture and performance characterisation of a helical antenna placed conformally outside an endoscopic capsule, and the characterisation in-silico, in-vitro and in-vivo of the telemetry system in alive and euthanised pigs. This method does not use the internal volume of the capsule, but does use an extra coating to protect the antenna from the surrounding tissue and maintain biocompatibility for safe use inside the human body. The helical antenna, radiating at 433 MHz with a bandwidth of 20 MHz within a muscle-type tissue, presents a low gain and efficiency, which is typical for implantable and ingestible medical devices. Telemetry capsule prototypes were simulated, manufactured and assembled with the necessary internal electronics, including a commercially available transceiver unit. Thermistors were embedded into each capsule shell, to record any temperature increase in the tissue surrounding the antenna during the experiments. A temperature increase of less than 1°C was detected for the tissue surrounding the antenna. The process of coating the biocompatible insulation layer over the full length of the capsule is described in detail. Data transmission programmes were established to send programmed data packets to an external receiver. The prototypes radiated at different power levels ranging from -10 to 10 dBm, and all capsules demonstrated a satisfactory performance at a data rate of 16 kbps during phantom and in-vivo experiments. Data transmission was achieved with low bit-error rates below 10-5. A low signal strength of only -54 dBm still provided effective data transfer, irrespective of the orientation and location of the capsule, and this successfully demonstrated the feasibility of the system

Bounds on RF cooperative localization for video capsule endoscopy

Wireless video capsule endoscopy has been in use for over a decade and it uses radio frequency (RF) signals to transmit approximately fifty five thousands clear pictures of inside the GI tract to the body-mounted sensor array. However, physician has no clue on the exact location of the capsule inside the GI tract to associate it with the pictures showing abnormalities such as bleeding or tumors. It is desirable to use the same RF signal for localization of the VCE as it passes through the human GI tract. In this thesis, we address the accuracy limits of RF localization techniques for VCE localization applications. We present an assessment of the accuracy of cooperative localization of VCE using radio frequency (RF) signals with particular emphasis on localization inside the small intestine. We derive the Cramer-Rao Lower Bound (CRLB) for cooperative location estimators using the received signal strength(RSS) or the time of arrival (TOA) of the RF signal. Our derivations are based on a three-dimension human body model, an existing model for RSS propagation from implant organs to body surface and a TOA ranging error model for the effects of non-homogenity of the human body on TOA of the RF signals. Using models for RSS and TOA errors, we first calculate the 3D CRLB bounds for cooperative localization of the VCE in three major digestive organs in the path of GI tract: the stomach, the small intestine and the large intestine. Then we analyze the performance of localization techniques on a typical path inside the small intestine. Our analysis includes the effects of number of external sensors, the external sensor array topology, number of VCE in cooperation and the random variations in transmit power from the capsule

Specific absorption rate and path loss in specific body location in heterogeneous human model

A multi-implant scenario is considered using insulated dipole antennas for specific locations such as the liver, heart, spleen and the kidneys where implants communicate with a pacemaker acting as a central hub. Wireless communication within human body experiences loss in the form of attenuation and absorption, and to identify these losses, the path loss is studied in this paper for an adult and child heterogeneous human model. Link performance is calculated to investigate the applicability of in-body communication. The specific absorption rate for all these locations is also studied to verify compliance with international safety guidelines

PROPAGATION CHARACTERIZATION OF IMPLANTABLE ANTENNA AT UWB FREQUENCY – A REVIEW

A technology of wireless body area network (WBAN) was invented in order to enhance the quality of healthcare management as well as to determine faster disease prevention. However, to obtain the real-time data of images and videos from inside the human body, an implantable device is required. Currently, the Medical Implant Communication System (MICS) is used, but, this system has limited data rate which is a narrow-band of 402 – 405 MHz. Thus, this study on Ultra Wideband (UWB) for implanted device is conducted as UWB offers a wide transmission bandwidth as well as high data rate. Knowledge of radio wave propagation behaviour inside human body is needed to perform the implantation. Past researches related to this topic are limited and those conducted focused only on the human torso. This paper aims to provide a better understanding on the characteristics of radio wave propagation inside the human body by using an implantable device at UWB frequency. It is also hoped that this study could be used as reference for future research on this subject

Propagation characterization of implantable antenna at UWB frequency – a review

A technology of wireless body area network (WBAN) was invented in order to enhance the quality of healthcare management as well as to determine faster disease prevention. However, to obtain the real-time data of images and videos from inside the human body, an implantable device is required. Currently, the Medical Implant Communication System (MICS) is used, but, this system has limited data rate which is a narrow-band of 402 – 405 MHz. Thus, this study on Ultra Wideband (UWB) for implanted device is conducted as UWB offers a wide transmission bandwidth as well as high data rate. Knowledge of radio wave propagation behaviour inside human body is needed to perform the implantation. Past researches related to this topic are limited and those conducted focused only on the human torso. This paper aims to provide a better understanding on the characteristics of radio wave propagation inside the human body by using an implantable device at UWB frequency. It is also hoped that this study could be used as reference for future research on this subject