Conventional colonoscopies are still their recommended screening tool, the doctors group said. On its website, the National Institutes of Health noted that virtual colonoscopies can't detect precancerous polyps smaller than 10 millimeters, and as doctors can't remove tissue samples during the procedure, if any suspicious findings are detected they'll have to order a follow-up conventional colonoscopy anyway.

But Farley pointed out most research suggests this would only apply to about 10 percent of people who are screened.


"Also you have to remember the cost of treating advanced colon cancer will be far more than the cost of treating a polyp. In the long run, you'll be saving money or a least not spending more money than you would have otherwise," he said.

But there is the radiation issue. The gastroenterologists group also worries that CT scans of the colon boost patients' exposure to ionizing radiation, which could lead to increased rates of radiation-induced cancers.

The average dose for the exam is about 10 mSv, equivalent to what someone would receive from background radiation over three years, according to the Radiological Society of North America's website. But the ACR said recent studies have shown CTC exams use one-third to one-half the radiation dose of a typical CT exam, and continue to fall.

According to American Cancer Society guidelines, CT colonographies are recommended about once every five years.

Farley was quick to point out that the ACR doesn't believe CT colonographies are a replacement for standard colonoscopies. Rather, it believes they're a way to boost compliance for screening and prevent unnecessary deaths from colon cancer, a largely treatable disease if caught early.

"For those people who are not getting screening, the choice is not a CT conolography versus a colonoscopy," Farley said. "It's a CT colonography versus nothing at all."

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