According to a new study appearing in the April issue of Radiology, CT colonography picked up unsuspected malignancies in more than one in 200 asymptomatic patients. More than half of these were located outside the colon and many were early-stage tumors.

The finding could add fuel to an already heated debate on the use of CT colonography, which has not yet been approved for reimbursement by Medicare or Medicaid. And it comes as the U.S. Food and Drug Administration prepares to hold a two-day public comment period starting Tuesday on the safe use of CT scans and other hi-tech imaging devices.

The new study suggests the technique is more of a comprehensive screening test that is not simply limited to the colon but can find important and unsuspected things outside of the colon at an earlier and presumably curable stage  Conventional colonoscopy -- in which a long tube is inserted through the rectum -- is not something most people look forward to and researchers have been trying to come up with alternatives.

One possible alternative might be CT colonography, in which a detailed picture of the colon is created by an X-ray machine linked to a computer. Although the bowel must be prepped beforehand, it is much less invasive than standard colonoscopy, which usually involves sedation while a doctor examines the colon through an inserted scope and camera.

Although the procedure is not yet approved under Medicare or Medicaid, it is recommended by the American Cancer Society for people at average risk for colorectal cancer. And recent research has suggested that it might be effective for people at higher risk as well.

On the other hand, one study found that it was less effective at correctly identifying colon cancers in people who've had a positive fecal occult blood test (FOBT), which means they have blood in their stool. A positive FOBT is a strong indicator that cancer might be present.