Computerized 3-dimensional localization of a video capsule in the abdominal cavity: validation by digital radiography

Background: Wireless video capsule endoscopy allows the noninvasive visualization of the small intestine. Currently, capsules do not provide localization information while traversing the GI tract. Objective: To report on the radiological validation of 3-dimensional localization software incorporated in a newly developed capsule. By using radiofrequency transmission, the software measures the strength of the capsule's signal to locate the position of the capsule. Setting: This study was performed at the University of Massachusetts Medical Center, Worcester, Mass. Patients: Thirty healthy volunteers consented to the experimental procedure. Design: After ingestion of the capsule, subjects had 5 sets of anteroposterior and lateral radiographs taken every 30 minutes while the software calculated the position of the capsule. By using the radiographs, we calculated the location of the capsule in the abdominal cavity and compared the results with those generated by the software. Results: Average error (and standard deviation) among the 3-dimensional coordinates was X, 2.00 cm (1.64); Y, 2.64 cm (2.39); and Z, 2.51 cm (1.83). The average total spatial error among all measurements was 13.26 cm(3) (22.72). There was a correlation between increased subject body mass index and the 3-dimensional software measurement error. Limitations: This study was performed in healthy volunteers and needs further validation in patients with small intestinal disorders. Conclusions: The new 3-dimensional software provides localization of the capsule consistent with radiological observations. However, further validation of the software's clinical utility is required with a prospective clinical trial.