Virtual colonoscopy

Virtual colonoscopy (also known as CT colonography or CTC) is a medical imaging procedure that 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. CT colonography is less invasive than traditional colonoscopy and has a lower risk of complications. However, if polyps or other abnormal growths are found during CT colonography, a traditional colonoscopy usually will be performed to remove them.

Procedure

The patient lies on a narrow table that slides into the center of a CT scanner. In some cases, a contrast material may be used to help visualize certain structures. Once inside the scanner, the machine's x-ray beam rotates around the patient. (Modern "spiral" scanners can perform the exam without stopping.)

A computer creates separate images of the body area, called slices. These images can be stored, viewed on a monitor, or printed on film. Three-dimensional models of the colon can be created by stacking the slices together.

Benefits and Risks

The benefits of CT colonography include: it is less invasive than traditional colonoscopy; it has a lower risk of complications; it can visualize the entire colon; it can detect polyps and cancer at an early stage.

The risks of CT colonography include: it can miss small polyps; it can produce false-positive results; it uses low doses of radiation, which have the potential to increase the risk of cancer; some people can have an allergic reaction to the contrast material.

See also

• Colonoscopy
• Computed tomography
• Diverticulosis
• Polyp
• Colon
• Rectum
• Cancer

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  CT colonography of a rectal mass
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  Virtual colonoscopy