Reducing the number of unnecessary and high-dose computed tomography in children could lower their overall lifetime risk of future imaging-related cancers by up to 62 percent, a US study said Monday.

Researchers reported in the journal JAMA Pediatrics that CT scans almost doubled among children under the age of 15 in the United States between 1996 and 2010 after an examination of CT utilization data from several US health-care systems.

They said CT use increased dramatically because it's effective and offers greater convenience than other imaging methods such as magnetic resonance imaging, which requires that a child remain still in a scanner for an extended period of time.

But radiation doses delivered by CT scans are 100 to 500 times higher than for conventional radiography, warned lead study author Diana Miglioretti of the University of California, Davis.

"There are potential harms from CT, meaning that there is a cancer risk, albeit very small in individual children," Miglioretti said in a press release. "So it's important to reduce this risk in two ways. The first is to only do a CT when it's medically necessary, and use alternative imaging when possible. The second is to dose CT appropriately for children."

The study found that the 4 million CT scans of the most commonly imaged organs conducted in children each year could result in approximately 4,870 future cancers. Reducing the highest 25 percent of radiation doses could prevent 2,090, or 43 percent, of these future cancers. By also eliminating unnecessary imaging, 3,020, or 62 percent, of cancers could be prevented, it said.

Miglioretti explained that children's organs are at an increased risk of cancer from CT scans because children still are growing and their cells are dividing rapidly.

She noted that physicians can reduce dosage amounts using a number of different strategies, including reducing scan length by focusing solely on the "zone of interest," the region requiring imaging. For example, when the zone of interest is the abdomen, physicians should avoid also scanning the pelvis. She said dosage guidelines for imaging pediatric patients should be followed closely.