Abstract
Ingestible medical capsules are used for non-invasive diagnosis and treatment of gastrointestinal (GI) tract diseases. For any task performed by a medical capsule (delivering drugs, collecting images, implanting a sensor, collecting bio samples, etc.), localization of the device is critical for optimal utility. Current methods enable approximate localization (a general location in 3D space), so physicians are aware if the capsule is in the stomach, small intestine, or colon. However, precise auto-localization (e.g. knowing the precise distance from the stomach) has been elusive as there is currently no way for an ingested capsule to precisely and accurately know its location. In this paper we discuss the development of a new medical capsule technology that uses suture odometry to measure the linear distance traveled by the capsule and can transmit that data wirelessly to an external device. A small spool of absorbable suture thread rotates as it is unwound while the capsule traverses the gastrointestinal tract, leaving behind a trail of suture. These spool rotations are tracked and mapped to a linear distance traveled by the capsule. This localization system was proven functional in a variety of environments, including freshly excised pig intestines with an average localization accuracy of 7.78 cm and an average precision of 8.24 cm over 9 m of intestine. The design is robust enough to perform properly even through intestinal bends, retrograde flow, intestinal sphincters, and is able to localize independently of any external hardware necessary for other localization methods.
