A method of identifying a polyp in a digital image of a colon, wherein said image comprises a plurality of intensities corresponding to a domain of voxels in a 3-dimensional space, is provided. The method includes providing the image with a set of 3 mutually orthogonal axes, providing a plurality of cutting planes each at a different orientation with respect to the image axes, centering, for each voxel in the image, each of the cutting planes about a central voxel, determining, for each of the plurality of cutting planes about each voxel in the image, an intersection of the cutting plane with the colon, and examining a trace of the cutting plane within said intersection, and marking, where the trace of each cutting plane is small and round, those voxels in the intersection for further analysis.