How is a Virtual Colonoscopy done?

Virtual colonoscopy is performed wherever the CT scanner or MRI unit is located—usually in the radiology department of a hospital or medical center. The procedure takes about 10 minutes and does not require sedation.

1. Patients will lie face up on a table.
2. A thin tube will be inserted through the anus and into the rectum. For CT, carbon dioxide gas will be pumped through the tube to expand the large intestine for better viewing. For MRI, contrast media will be given rectally to expand the large intestine.
3. The table will move through the CT scanner or MRI unit to produce a series of cross-sectional images of the colon.
4. At various points during the procedure, the doctor may ask patients to hold their breath to steady the images.
5. The procedure will be repeated while patients lie face down.

After the procedure, cross-sectional images taken by CT or MRI are processed to create three-dimensional, computer-generated images of the large intestine. A radiologist evaluates the results to identify any abnormalities. If abnormalities are found, conventional colonoscopy may be performed the same day or at a later time.