Scientists say children who undergo computed tomography (CT) scans triple their risk of developing a brain tumour or leukaemia.
CT scans use x-ray and digital technology to take an image of the inside of our bodies. They are used to diagnose serious illnesses, for planning surgery and to check for brain injuries after accidents.
A UK study by Newcastle University has found that children who received two or three CT scans before they turned 15 were three times more likely to develop brain cancer.
Dr Mark Pearce from the university said that children are particularly sensitive to the radiation levels of CT scans.
"CT scans are very useful but they have relatively high doses of radiation, particularly when compared to x-ray. They have about 10 times the dose used in x-ray," he said.
The study analysed 180,000 children who underwent CT scans in the UK between 1985 and 2002.
While CT scans are incredibly important in many medical cases, the study authors say alternative procedures need to be considered where possible.
"Although clinical benefits should outweigh the small absolute risks, radiation doses from CT scans ought to be kept as low as possible and alternative procedures, which do not involve ionising radiation, should be considered if appropriate," they wrote in the study.
While Dr Pearce said reducing radiation in CT scans “should be a priority”, he pointed out that the risk of getting brain cancer was still small.
For every 10,000 children under 10 who had a head CT scan, one additional brain tumour and one additional leukaemia case would be recorded in the following 10 years.
Professor Ian Olver, medical oncologist and CEO of Cancer Council Australia, said experts have long been aware that radiation can have adverse effects.
"The lesson to be learnt is that in children, CT scans should be ordered only when they are absolutely necessary," he said.
But he warned parents not to fret if their child needs a CT scan.
"Parents need to understand that if a scan is necessary for the immediate wellbeing of a child, this sort of result shouldn’t put them off having the scan done – it’s up to clinicians to make sure they can justify each scan."