Ingestible Sensing Capsule with Magnetic-Based Localization Using a Wearable Belt

Wireless ingestible sensing capsules are of high relevance in the medical field due to their capability to measure biochemical parameters along the gastrointestinal (GI) tract and the potential to associate these with health-related conditions. Obtained sensor information is much more valuable when accompanied by accurate localization, since propagation speed can vary widely. However, most capsule localization systems presented in literature are either not accurate enough or imply bulky external units difficult to wear during daily life activities. Here, a novel ingestible sensing capsule 'GISMO-LOC' for pH and oxidation reduction potential sensing is presented. It features magnetic localization functionality enabled by a wearable transmitter belt. An in-vitro evaluation of the biochemical sensors confirmed the expected biochemical sensing functionality of the capsule. Evaluations of the location estimation in controlled conditions resulted in a mean absolute error (MAE) of 5.7 mm in the volume of interest. A GI trajectory reconstruction using a robot is also presented, with a MAE of 3.8 mm. An on-human evaluation during typical daily life activities resulted in most absolute errors below 2 cm for 'light' activities, 3 cm for 'moderate' activities and 4 cm for high-motion activities such as running. An evaluation of the belt comfort showed volunteer willingness to wear the belt during one week in daytime, while improvement aspects were identified to enable its use during the night. Finally, a limited in-vivo validation of the localization in an animal model was successfully performed. GISMO-LOC is therefore presented as a novel tool for GI tract related research.