Automated centerline tracking of the human colon

Early detection of colorectal polyps can improve morbidity and mortality due to cancer of the colon. The colon centerline can be used to expedite examination of the endoluminal surface for colorectal polyps. An automated technique has been developed that calculates the colon centerline from rectum to cecum from helical computed tomography slices of fully insufflated colons. Volume growing is initiated by indicating a seed point in the rectum, air voxels are grown and tagged with growth step numbers. The centers of mass of grown voxels with similar growth step numbers are used as a `forward' centerline. This procedure is repeated by growing from the cecum to the rectum to generate a `backward centerline'. The forward and backward centerlines are averaged to produce the calculated centerline. The technique was evaluated on a clinical colon case by comparing the calculated centerline with points indicated by 2 radiologists. Root mean square differences between the computed and indicated points were small (4 - 5 mm) and comparable to inter-observer differences. Results indicate that with this technique the centerline of the colon can be accurately and quickly calculated.