Computed Tomography scans (also known as CT or CAT scans) use special x-ray equipment to create cross-sectional images that appear as "slices" of the body and organs. When the colon is distended with gas, the resulting images can be viewed on a computer workstation, allowing the inner walls of the colon to be evaluated with 2-D and 3-D views. This gives a view of the colon similar to that seen during colonoscopy, which is a more invasive screening tool.
Virtual colonography can also be used as a screening test to evaluate individuals with a relatively low risk of colon cancer. You should consult with your personal physician as to which screening procedure is most appropriate for you.
WHAT SHOULD I EXPECT?
During the exam you will lie on a table that will move you into the doughnut-shaped scanner. Your technologist will watch you through an observation window and will be able to communicate with you at all times. At the beginning of the procedure, a tube will be placed in the rectum to allow the colon to be filled with carbon dioxide gas. This inflation is necessary to better evaluate the walls of the colon for possible polyps or masses. Once the colon is distended, you will be instructed on breath holding during the acquisition of images. You may hear humming, buzzing, or clicking sounds as the CT machine moves to reposition you for the images. Two sets of images will be obtained, the first with you on your back and the second while on your stomach.
Remaining still and following the breathing instructions are very important in order to obtain clear images.
When scanning is complete, the technologist will return to help you from the table. You may eat normal meals unless other tests are scheduled. Your exam will take about 20 minutes, after which you will be able to return to your normal activities.