ISLAMABAD: Exposing a child to the nuclear radiation from two or three computed tomography (CT) head scans may triple its risk of developing brain cancer later in life.
The risk of developing cancer comes from the ionizing radiation used in CT scans. The risk is higher in children, who are more radiosensitive than adults.
A 20-year study published on Thursday also found that a child exposed to the cumulative radiation of between five and 10 CT scans is three times more likely than an unexposed child to develop leukemia.
While the absolute risk of cancers developing after a CT scan, a diagnostic technique often used on children with possible head injuries, is still small, the researchers advise lowest possible radiation doses with alternatives to ionizing radiation.
"This work emphasizes the very great importance of only using this form of imaging when it has a strong medical justification," says Bruce Armstrong, professor of public health at Sydney University in Australia.
One alternative to a CT scan is ultrasound, which involves no radiation, but is less accurate. A study published last month found that it may also be safe to postpone CT scans in some cases of childhood head injuries.
A total of 74 out of 178,604 patients were diagnosed with leukemia and 135 of 176,587 were diagnosed with brain cancer, and the researchers calculated the relative risk of leukemia increased by 0.036 for every mGy received, while the increased risk of a brain tumor was 0.023.
"Alternative diagnostic procedures that do not involve ionizing radiation exposure, such as ultrasound and MRI (magnetic resonance imaging) might be appropriate in some clinical settings," he added.