Patients who are exposed to the highest doses of radiation from a CT scan are at the greatest risk, but even a less powerful scan still doubles the risk for a brain tumour.
The use of CT technology has ballooned in the past 20 years because it makes diagnosis much easier as it gives a three-dimensional image of a problem area, typically the brain, or abdomen and pelvis.
But it also releases much higher levels of radiation than a standard x-ray, and this is putting many more people, and especially children, at risk.
When researchers looked at the health records of 168,394 children who had had one or more CT scans, they discovered that cancer cases were 1.5 times higher than they had anticipated. They also found a direct correlation between the radiation doses and cases of malign and non-malignant tumours.
Surprisingly, the scans didn't increase the risk for leukaemia, another cancer known to be caused by radiation exposure.
The risk estimation could be slightly skewed as some of the children may have been scanned because they were at risk of developing cancer anyway, although that does throw into question the justification for zapping them with high doses of radiation in the first place.
(Source: JNCI: Journal of the National Cancer Institute, 2018; doi: 10.1093/jnci/djy104)