In Vivo Characterization of a Wireless Telemetry Module for a Capsule Endoscopy System Utilizing a Conformal Antenna.

Julia Faerber,Marc P Y Desmulliez,Sandy Cochran,Adrian R Ayastuy Rodriguez,Paul Record,Sadeque Reza Khan,Benjamin F Cox,Sumanth Kumar Pavuluri,Richard Eddie Clutton,Ciaran Connor,Rachael Mcphillips,Rachael Gregson,Holly S Lay,Gerard Cummins

doi:10.1109/tbcas.2017.2759254

Abstract

This paper describes the design, fabrication, packaging, and performance characterization of a conformal helix antenna created on the outside of a capsule endoscope designed to operate at a carrier frequency of 433 MHz within human tissue. Wireless data transfer was established between the integrated capsule system and an external receiver. The telemetry system was tested within a tissue phantom and in vivo porcine models. Two different types of transmission modes were tested. The first mode, replicating normal operating conditions, used data packets at a steady power level of 0dBm, while the capsule was being withdrawn at a steady rate from the small intestine. The second mode, replicating the worst-case clinical scenario of capsule retention within the small bowel, sent data with stepwise increasing power levels of -10, 0, 6, and 10dBm, with the capsule fixed in position. The temperature of the tissue surrounding the external antenna was monitored at all times using thermistors embedded within the capsule shell to observe potential safety issues. The recorded data showed, for both modes of operation, a low error transmission of 10-3 packet error rate and 10-5 bit error rate and no temperature increase of the tissue according to IEEE standards.

Highlights

W IRELESS capsule endoscopy (WCE) is an accepted diagnostic modality for imaging the gastrointestinal tract (GI) complimenting conventional endoscopy
The results of the static power devices show that the variation in RSSI is the highest when the capsule is inserted to the furthest point (60 cm) from the stoma and is moved to the stop
As the capsule nears the stoma there is a reduction in signal power variability observed in each capsule, which can be due to multiple factors such as increased dominance of a single tissue property, reduction in tissue mass surrounding the capsule as well as distance to the RX

Summary

Introduction

W IRELESS capsule endoscopy (WCE) is an accepted diagnostic modality for imaging the gastrointestinal tract (GI) complimenting conventional endoscopy. The small size of these capsules (typically 11 mm diameter, 26 to 31.5 mm length) makes them easy to swallow and allows access to the small bowel, which is difficult to reach using conventional endoscopy. Their size has led to greater patient acceptance, which is beneficial for improved diagnosis and management of gastrointestinal disorders. One modality being investigated by the Sonopill project [5] is the use of combined ultrasound (US) and optical imaging to improve the early diagnosis of a wide variety of gastrointestinal disorders, such as Crohn’s disease or colorectal cancer, as US enables the detection of subsurface neoplasms amongst other pathologies [3], [5], [6]

Results

Discussion

Conclusion