Tracking wireless bio-medical sensors: Result validation with the Bland-Altman plots

In this paper, we present a series of experimental results of tracking an embedded sensor object similar in physical characteristics to telemetry capsules in the gastro-intestinal (GI) tract using radio frequency (RF) signals. A fair description of implementation detail is given in the body of the paper while focus is on analyzing the experimental results. Experiments were based on a test capsule transmitting radio frequency (RF) signals pulses at 433 MHz; a Receiver based on microcontroller circuits with ADC capability and a means of transferring the received signal strength intensity (RSSI) voltage converted to digital, from the microcontroller to the personal computer (PC). Primary focus is a unique and practical way of achieving the task of dynamically identifying the location of the capsule in real-time as it traverses the experimental duct. Tracking results for experiments in liquid simulating the electrical behavior of the lower portion of the intestines yielded an average error of about 18.9%. These results were validated with the Bland-Altman plots using manual measurements as gold standard. Overall analysis shows that the end result of the algorithm is quite suitable for tracking ingestible telemetry capsules in the GI tract.