During the procedure, the patient lays down on their back. A thin tube is inserted into the rectum, and air is introduced through the tube to distend the colon for optimal viewing. The patient then moves through a CT scanner that produces a series of 3D cross-sectional images along the length of the colon. A single breath hold of 15-20 seconds is required during the scan to avoid distortion of the images. The same scan is then repeated with the patient lying on their stomach. The tube is then removed and the procedure is over.