Challenges in the Localization of a UHF Radio Pill in the Gastro-Intestinal Tract

Abstract

Visual and chemical investigations in the gastro-intestinal tract using injected "pill" sized sensors are challenging. The throughput takes between 24 and 48 hours and a precise location accuracy to less than 5 cm is necessary for keyhole surgery. Model and computational experiments using a 433 MHz subsurface transmitter in a saline (conductivity = 0.2 S/m) tank show that location accuracy is compromised by non-conducting boundaries between internal organs connected by non-conducting interstitial tissue. The internal transmitter profile changes significantly by the presence of insulating boundaries modelled by non-conducting boundary in an otherwise uniform conducting medium. A worn sensor array in the front of the abdomen can define the location of a GI pill only if there is significant information about the internal organ configuration.