Visibility map: A new method in evaluation quality of optical colonoscopy

Abstract

Optical colonoscopy is performed by insertion of a long flexible endoscope into the colon. Inspecting the whole colonic surface for abnormalities has been a main concern in estimating quality of a colonoscopy procedure. In this paper we aim to estimate areas that have not been inspected thoroughly as a quality metric by generating a visibility map of the colon surface. The colon was modeled as a cylinder. By estimating the camera motion parameters between each consecutive frame, circumferential bands from the cylinder of the colon surface were extracted. Registering these extracted band images from adjacent video frames provide a visibility map, which could reveal uncovered areas by clinicians from colonoscopy videos. The method was validated using a set of realistic videos generated using a colonoscopy simulator for which the ground truth was known, and by analyzing results from processing actual colonoscopy videos by a clinical expert. Our method was able to identify 100% of uncovered areas on simulated data and achieved with sensitivity of 96% and precision of 74% on real videos. The results suggest that visibility map can increase clinicians’ awareness of uncovered areas, and would reduce the chance of missed polyps.