Computed tomographic colonography

Computed Tomographic Colonography (CTC), also known as virtual colonoscopy, 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. CTC can provide detailed images of different types of tissue, such as fat, muscle, and blood vessels, all at the same time.

Procedure

The patient lies on a narrow table that slides into the center of a CT scanner. Once inside the scanner, the machine's x-ray beam rotates around the body. (Modern "spiral" scanners can perform the exam without stopping.) A computer creates many 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 often help the doctor interpret the images.

Preparation

Before the procedure, a patient may be asked to take laxatives or other oral agents at home to clean out the colon. On the day of the procedure, the patient lies on the side on a table and the doctor inserts a small tube into the rectum to inflate the colon with air for better viewing.

Risks

While CTC is generally safe, it does expose the patient to low doses of radiation. The risk of cancer from radiation exposure is thought to be small, but the risk may increase with numerous CT scans. Other risks include a very small risk of perforating the colon during the procedure.

Benefits

CTC is less invasive than traditional colonoscopy and doesn't require sedation. It's also faster, typically taking 10 minutes, and patients can return to their normal activities after the procedure.

Limitations

CTC may not be as good as colonoscopy at finding small polyps and cancers. It also can't remove polyps or treat certain diseases, which traditional colonoscopy can do.

See Also

• Colonoscopy
• Colorectal Cancer
• Diverticulosis
• Polyps

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