Improving the Localization and Coverage of Colonoscopy with Motion Tracking and Surface Mapping

Abstract

Colonoscopy is essential for colorectal cancer screening and disease surveillance. It can remove pre-cancerous colon polyps to reduce a patient’s cancer risk. This thesis aims to improve colonoscopy’s localization using motion tracking and colonoscopy’s coverage using surface mapping. Chapter 4 describes an endoscope motion tracker that records the scope’s insertion length, rotation, and speed during a colonoscopy. The endoscope tracker’s motion record can be combined with the endoscope’s video to localize colon polyps or cancers. In the future, the device could record highly skilled manoeuvres performed by endoscopists to help train medical residents. It is difficult to image the colon’s mucosa because the colonoscope’s camera has a limited field of view. Chapter 3 uses a 180° fisheye camera to unwrap high resolution panoramas of a colon phantom. The panoramas are then combined into a mosaic map of the colon phantom’s surface. The colon’s surface is approximated as a cylinder. Follow up experiments could test our mapping algorithm using imagery from a wide-angle, high-definition colonoscope. Chapter 2 describes another technique to localize locations where polyps have been removed—blood vessel landmarks. Colonic blood vessels from a pig were imaged to determine if they could be used to fingerprint locations on the colon’s wall. Blood vessels are also useful image features for surface mapping. The proof-of-concept experiments successfully imaged large arteries but further work is needed to image the small capillaries in the colonic mucosa and to image the veins. In summary, we have visualized colonic blood vessels to test if they could be useful landmarks, tested using an extended field of view camera to create an unwrapped map of the colon wall, and designed an endoscope tracker to help localize abnormal tissue. Combining the endoscope tracker with the other two techniques should make is possible to accurately map the colon.