WASHINGTON, June 9 (Xinhua) -- Children undergoing complex imaging tests like computed tomography (CT) scans for heart problems may have higher cancer risks over their lifetime, according to a study released Monday by the American Heart Association journal Circulation.
These tests, also including cardiac catheterization procedures using video X-rays called fluoroscopies, may expose children to higher doses of radiation than standard X-rays do, researchers at Duke University Medical Center said.
Radiation from standard X-rays, however, is relatively low and doesn't significantly raise lifetime cancer risks for most young children, they said.
"There are definitely times when radiation is necessary," Kevin Hill, lead author and cardiologist and assistant professor of pediatrics in the cardiology division at Duke, said in a statement.
"But it's important for parents to ask and compare in case you can avert potentially high exposure procedures. Often, there are alternative or modified procedures with less radiation, or imaging may not actually be necessary," he said.
The researchers followed 337 children under age six who had surgery for heart disease, since children with heart disease are exposed to more imaging tests than most young patients. These children received almost 14,000 imaging procedures, including X- rays, cardiac catheterizations and CT scans.
The researchers reviewed medical records to find the most common imaging procedures, calculated how much radiation organs absorb during each procedure, then analyzed lifetime cancer risks based on the amounts of each procedure's exposure.
They found that for the average child in the study, the cumulative effective dose of ionizing radiation was relatively low, less than the annual background exposure in the United States.
However, some children with complex heart disease were exposed to large cumulative doses that increase the estimated lifetime risk of cancer up to 6.5 percent above baseline.
In all, lifetime cancer risk increases ranged from 0.002 percent for chest X-rays to 0.4 percent for complex CT scans and cardiac catheterizations.
Although X-rays accounted for 92 percent of all imaging exams, more complex tests like CT scans accounted for 81 percent of overall radiation exposure, the researchers said.
Specially, girls have double the cancer risks of boys because they're more prone to breast and thyroid cancers.
"Simple awareness is one of the greatest means to reducing exposure," Hill said. "Healthcare providers should consider tweaking protocols to limit radiation doses and balance risks and benefits of every imaging study they do."