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What are CT scans and why are children sensitive to them?

A CT scan uses X-rays to provide images of what is hard and soft inside a body. These X-rays are taken by a rotating ring that is moved around the body. A computer can then turn the X-ray images into 3-D images. As CT scans involve many X-rays, they use higher levels of ionising radiation than other types of medical imaging.

A study led by Professor John Mathews has indicated that there is a higher risk of a person developing cancer in later life if they were exposed to ionising radiation from a CT scan as a child.1

Radiation exposure is a concern in both adults and children in terms of increased risk of cancer. However, children have a greater sensitivity to ionising radiation than adults, as demonstrated in epidemiological studies of exposed populations. This is because rapidly growing cells are more likely to be damaged by ionising radiation. Children also have a longer life expectancy which means there is a longer time for the effects of any radiation damage to occur.

However, it is also important to ensure that CT scans are undertaken for time-critical conditions and when there are evidence-based protocols for conditions or a given disease. For example, in the case of a serious head injury. The sensitivity of children and young people to ionising radiation means that appropriate consideration needs to be given to whether:

  • A CT scan now will improve the child’s health care
  • Previous imaging is available that could provide the information needed
  • There are other imaging options that could be used
  • A warranted CT scan be done using a ‘kid-sized’ radiation dose
  • The benefits and risks have been explained to parents and carers.

1. Mathews JD, Forsythe AV, Brady Z, Butler MW, Goergen SK, Byrnes GB,, Cancer risk in 680,000 people exposed to computed tomography scans in childhood or adolescence: data linkage study of 11 million Australians. BMJ.2013;346:2360

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