A method of detecting lesions and polyps in a digital image, wherein said image comprises a plurality of 3D volume points, is provided. The method includes identifying a surface in the image, and for each point in the image, calculating a first curvature measure, forming a set of rings of points about each point, each ring being of equal geodesic distance from a center point for the ring, calculating, for each ring, a standard deviation of the first curvature measure, and selecting those rings with a minimum standard deviation for the first curvature measure. A first curvature slope is calculated for the selected rings, those points where the curvature slope departs from the pattern expected for a polyp or lesion are deleted from the surface.