1. A computer-assisted method for detecting surface features in a virtual colonoscopy, comprising: providing a three-dimensional construction of a computed tomography colonography surface; creating a path along the teniae coli from the proximal ascending colon to the distal descending colon on the colonography surface; forming an indexed computed tomography colonography surface using the created path; and registering the supine and prone scans of the computed tomography colonography surface using the indexed computed tomography colonography surface.