A method for evaluating sensitivity of electromagnetic localization systems for wireless capsule endoscopes

This paper studies the use of electromagnetic induction in localization of wireless capsule endoscopes (WECs). There is still currently a need for an accurate localization system to enable localizing possible findings in the gastrointestinal tract, and to develop an active steering system for the capsule. Developing an optimal localization system requires the sensitivity of the system to be analyzed. In this paper, three different coil geometries are modelled with a computer simulation platform, and their sensitivities and target responses are compared. In order to do that, a formulation for the sensitivity based on the dipole model approximation is presented. The first coil array is based on literature and is used as a reference. The second array presents how having more transmit-receive channels in the array effects the sensitivity. The third coil array simulates the effect of increasing the field excitation intensity in different directions by using a three-axial Helmholtz array. In addition, both proposed coil arrays utilize larger coils than the reference. As a result, it seems that both increasing the coil size and the number of field projections interrogating the target increase the overall sensitivity in the region of interest and the target response. The findings suggest that an optimal coil array could utilize both large coils and multiple transmit-receive channels to increase the number of independent fields incident onto the target.

I. Introduction

Endoscopy is a commonly used technique in which the gastrointestinal (GI) tract of human is examined. The conventional endoscope cannot reach the small intestine which prevents diagnosing many diseases that appear there, such as Chron's disease, celiac disease, irritable bowel syndrome or different types of cancer [1]. Because of this, the first wireless capsule endoscope (WEC) was developed in 2001. It is a small, capsule-shaped device that is swallowed by the patient. It travels through the whole GI tract due to gravitation and natural peristalsis and takes thousands of pictures during its way. These pictures are transmitted to a recording device outside the body and can be visualized on a computer screen. [2]