A Wireless Insufflation System for Capsular Endoscopes

Abstract

Swallowable capsule-based cameras (e.g., the Given Imaging PillCam and competitors) are rapidly becoming the gold standard for diagnosis in the gastrointestinal (GI) tract. However, definitive diagnosis is still often precluded by the inability to control capsule position and orientation. This has inspired a number of active positioning strategies including augmenting the capsule with legs or other appendages, or incorporating magnets which can apply forces and torques in response to an external magnetic field. Furthermore, the loose, mucous coated, elastic intestine is generally deflated during capsule passage, making it challenging to view the entire internal surface adequately without the insufflation that is relied upon in traditional endoscopy. To address these challenges, we propose a new fluid-powered system that permits insufflation from a wireless capsule platform. This is accomplished by carrying a small reservoir of biocompatible liquid onboard the capsule which vaporizes and expands when released through a small onboard solenoid valve. The internal components of the capsule consist of two 3V Lithium coin cell batteries (VL621, Panasonic, Inc.) which charge 3 Tantalum capacitors (TAJB157M006R, AVX Corporation, Inc.) that fire the solenoid valve (S120, Lee Company, Inc.). In our initial proof-of-concept study, we have packaged all components in a 26 mm long by 11 mm diameter capsule. The fluid used in initial experiments is biocompatible Perfluoropentane, although any of a variety of biocompatible fluids that can be liquefied with light pressurization may be used. Perfluoropentane, developed for lung lavage, is a liquid at room temperature and becomes gaseous at body temperature. We note that pneumatic pressure produced in this way may be used for a variety of objectives, including powering biopsy collection devices or other mechanisms within the capsule, or being vented to inflate the intestine. In initial experiments, we have harnessed the pressure to inflate a balloon at the front of the capsule which can distend tissue and thereby improve image quality. In experimental tests, only 0.2 ml of fluid was consumed in inflating the balloon to sufficient pressure to distend porcine intestine (see http://research.vuse.vanderbilt.edu/MEDLab for images of these experiments). Optimization of the capsule body and electrical components is currently underway. Including a wireless camera, all components are expected to fit within the dimensions of a commercial PillCam.