Overuse of CT scans and the subsequent exposure to dangerous radiation from the potent X-rays could raise the risk of cancer, researchers warned Wednesday.

David Brenner and Eric Hall of Columbia University Medical Center in New York write in the New England Journal of Medicine that millions of Americans, especially children, undergo needless CT scanning, or computed tomography, exposing themselves to risks rather than advantages.

The two researchers warn that in a few decades, as many as 2 percent of cancers in the United States may be due to radiation from the tens of millions of CT scans given now.

The authors cited previous studies which showed that as many as one third of diagnostic tests are unnecessary or possibly replaceable with an alternative technique – that amounts to 20 million adults and more than one million children having needless CT scans that put them at risk.

According to statistics, three million scans were performed in the US in 1980, an infinitesimal figure compared to the 62 million scans done in 2006. As a result of this increase, the researchers said, the average personal exposure to radiation has doubled since 1980.

More than four million of last year’s CT scans were in children. Children are more susceptible to radiation, because their tissues are more sensitive to it.

“It has been estimated that about 0.4 percent of all cancers in the United States may be attributable to the radiation from CT studies,” the authors wrote in their study. “By adjusting this estimate for current CT use, this estimate might now be in the range of 1.5 to 2.0 percent,” when tumors caused by current exposures begin to appear.

The two authors emphasized that, while the current radiation exposure is not a reason for alarm yet, doctors should be more selective when ordering a CT scan and not rely exceedingly on this technique. They suggested alternatives such as ultrasound and magnetic resonance imaging scans.

CT scans produce three-dimensional X-ray images of anatomical structures within the body that can reach a greater depth and minutiae than conventional X-rays. it has been particularly important in detecting and helping diagnose cancer.