Automatic Colonic Polyp Detection by the Mapping Using Regional Unit Sphere

Colonic polyps appear like elliptical protrusions on the inner wall of the colon. The many proposed algorithms assumed the shape of a polyp as a spherical cap, so the algorithms are not flexible when the polyps are irregular shapes. In this paper, we propose a mapping using regional unit sphere (MuRUS) method to overcome the problem caused by unexpected polyp shapes. The MuRUS has shape invariant and size invariant properties. Our method was applied to colon CT images from 3 7 patients each having a prone and supine scan. There are 45 colonscopically confirmed polyps. The results obtained by our algorithm were compared with those gold standards. 100% of polyps >= 10 mm in diameter were detected, 90% of polyps >= 6 mm in diameter were detected and 70% of polyps < 6 mm in diameter were detected at 7.0 FPs per patient.