The medical imaging tests used children’s cancer treatment can expose them to worrying levels of radiation, according to a study conducted at the Hospital for Sick Children in Toronto, Canada.

Researchers evaluated the records of 150 children who underwent cancer treatment in 2001 and analysed the amount of radiation they were exposed to.

The study findings showed that over a five-year period, the children were exposed to radiation doses ranging from one millisievert (mSv) to 642mSv. The median dose for the study group was 61mSv, and 41% of the children were exposed to more than 100mSv of radiation dose.

The researchers estimate that a 10-year-old who is exposed to 61 mSv of radiation will have their lifetime cancer risk increased by 1.2%, while those who are exposed to more than 100 mSv will have their lifetime cancer risk increased by 2%.

The researchers added that although medical imaging is a necessary part of treatment of cancer, parents should inquire why a test is conducted and if any radiation-free alternatives are available.