Virtual Colonoscopy

Virtual colonoscopy (VC) uses x rays and computers to produce two- and three-dimensional images of the colon (large intestine) from the lowest part, the rectum, all the way to the lower end of the small intestine and display them on a screen. The procedure is used to diagnose colon and bowel disease, including polyps, diverticulosis, and cancer. VC can be performed with computed tomography (CT), sometimes called a CAT scan, or with magnetic resonance imaging (MRI).

source: http://digestive.niddk.nih.gov/ddiseases/pubs/virtualcolonoscopy/index.htm