Propagation, Power Absorption, and Temperature Analysis of UWB Wireless Capsule Endoscopy Devices Operating in the Human Body

With the increasing use of wireless capsule endoscopy (WCE) devices in healthcare, it is of utmost importance to analyze the electromagnetic power absorption and thermal effects caused by in-body propagation of wireless signals from these devices. This paper studies the path loss, specific absorption rate (SAR), specific absorption (SA), and temperature variation of the human body caused by an impulse-radio ultra-wideband (UWB) based WCE operating inside the human abdomen. In addition, the design and in-body performance of an UWB antenna with dimensions of 11.85×9×1.27 mm and operating from 3.5 to 4.5 GHz is described in this paper. Path loss is evaluated using both experimental and simulation based methods to characterize the in-body propagation channel. The experimental setup uses a pig's abdominal tissue samples to demonstrate the propagation characteristics of human tissue while a voxel model of the human body consisting of human tissue simulating materials is used in the simulations. The tissue properties, such as relative permittivity, are characterized according to the incident signal frequency and age of the tissue sample during simulations. The SAR and SA variations for different positions of the WCE device inside the colon and the small intestine of the human body model are analyzed using the finite integration technique as the discretization model. The dependency of the electromagnetic effects on the antenna positioning is investigated by using different positions of the antenna inside the human body.