A study on Virtual colonoscopy was published in Wednesday’s issue of New England Journal of Medicine. It’s the largest study to estimate the accuracy of the technology; the research was sponsored by the National Cancer Institute and had 2,600 men and women tested at 15 medical centers. Dr. Daniel Johnson of the Mayo Clinic in Scottsdale, Arizona and colleagues are the ones who initiated and took care of the study.

Colon cancer is the third most common and second most deadly cancer in the United States. Screening for polyps is recommended at age 50, but traditional colonoscopies are so unpleasant that many people avoid them.

Traditional colonoscopies are performed by gastroenterologists using a flexible tube that is passed through the bowel. A device on the end of the tube can remove polyps for testing right then and there.

Virtual colonoscopy (VC) on the other hand, is a not so very old medical imaging procedure which uses x-rays and other machines and computers to produce three-dimensional images of the colon (large intestine) from its lowest part, called the rectum up to the lower end of the small intestine. VC is more comfortable than conventional colonoscopy for some people because it does not use a colonoscope. As a result, no sedation is needed, and the patient can return to his/her usual activities or go home after the procedure without the aid of another person.

It was recommended for anyone who needs screening colonoscopy. While the test still requires what doctors politely call "bowel preparation," the new technology is much easier and more comfortable for patient.

Participants underwent a virtual colonoscopy followed by a standard colonoscopy. Researchers found the virtual colonoscopy is actually very accurate, detecting 90 percent of polyps 10 millimeters or more in diameter. Problems occur though once the polyps have a smaller diameter. The 10 millimeter polyps progress to cancer at a rate of 1 per cent every year. Johnson and colleagues note that fewer than 2 per cent of polyps smaller than 5 millimeters have features that suggest they are precancerous. Should polyps be found during a VC, any growth will eventually be removed during the classical colonoscopy procedure. So the old methods cannot be left behind.

Regarding the VC, Dr. Durado Brooks, director of prostate and colorectal cancer for the American Cancer Society explained the following: "It will miss some abnormalities, but even colonoscopy is not a perfect tool. Studies of back-to-back colonoscopy show miss rates of between 2 and 11 percent.”

However Johnson admits that radiologists require specialized training and experience before they're ready to perform screening CT colonography. But he says that kind of training is readily available.
Colonoscopies cost up to $3,000. The X-ray test costs $300 to $800. All in all, the procedure is used to diagnose colon and bowel disease, including polyps, diverticulosis and cancer.