As a screening tool for colon cancer, "virtual" colonoscopy may soon be considered sensitive and accurate enough for widespread use. Unlike traditional optical colonoscopy, which involves inserting an endoscope into the colon, virtual colonoscopy is performed by taking a series of computed tomography images of the intestine.

In a recent study, 1,233 people with no symptoms of colon cancer and an average risk of the disease underwent both virtual and optical colonoscopy on the same day. The sensitivity of virtual colonoscopy at detecting polyps 6 mm, 8 mm, and 10 mm in diameter was 89%, 94%, and 94% respectively. The sensitivity of optical colonoscopy for polyps of the same sizes was similar: 92%, 92%, and 88%.

Two of the 554 polyps detected turned out to be malignant. Virtual colonoscopy revealed them both; optical colonoscopy detected only one of them.

The special X-ray equipment used in virtual colonoscopy produces cross-sectional images of the colon from different angles. A computer program then assembles the images into a single film showing the colon's entire length. If the health care provider detects a polyp, the patient will probably undergo standard colonoscopy, which can be used to obtain a tissue specimen for biopsy.

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