Intra-operative monocular 3D reconstruction for image-guided navigation in active locomotion capsule endoscopy

Wireless capsule endoscopy (WCE) can be considered an example of `disruptive technology' since it represents a bright alternative to traditional diagnostic methodologies. However, currently available clinical products are passive devices whose locomotion is driven by natural peristalsis, with the drawback of failing to capture the images of potential pathological gastrointestinal tract regions, due to the impossibility to control the camera's motion and orientation. As a consequence, many research groups are working to develop active locomotion devices and endoscopic platforms that allow WCE to be performed in a totally controlled manner. In this paper we propose a system to reliably calibrate a Shape-from-Shading system to recover the unknown scale factor immediately prior to a WCE procedure. The system would allow to reconstruct in a metrically accurate fashion the surfaces obtained intraoperatively from the WCE capsule, which can be exploited for accurate trajectory planning and ultimately automatic WCE active capsule navigation. To the best of our knowledge, this is the first practical system for Shape-from-Shading calibration aimed at guidance applications that will finally be applied to an endoscopic active locomotion platform developed by the authors.