Radiation risks in children

High levels of ionising radiation can contain enough energy to change cells in the body. For this reason, there are concerns about the possible long-term risks, such as cancer, with medical imaging — particularly with CT scans.

Radiation risks in children are greater than in adults

Fact sheet: What you need to know about CT scans for children

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This summarises key information for parents and caregivers of children who need a CT scan, including how to prepare your child for a CT scan.

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Although the risk of cancer is generally small, as a principle it is best to limit your radiation exposure, especially in children. This is something your doctor, imaging specialist and technologist (radiographer) will take into account before your child has imaging.

Generally, the risk of developing cancer in the longer term as a result of excessive radiation exposure during childhood is greater than the risk from similar exposure during adulthood. This is because a young person's cells grow rapidly and are more susceptible to damage. Young people also have more years of life ahead of them during which damaged cells could turn into cancer.

Understanding the risk

While an association between cancer risk and exposure to radiation from medical imaging exists, each decision to undertake a CT scan needs to be considered on its own merit. Past and potential exposures are not relevant to the consideration of benefits and risks of exposure from each individual CT scan.

In an example of two patients scheduled for CT scans, one with a previous history of several CTs and the other with no previous exposure to diagnostic radiation, the patient with previous exposure has the same attributable risk associated with the scheduled CT as the patient that has never been previously exposed to diagnostic imaging radiation.

This does not mean that previous medical imaging should not be considered in regard to patient management, as previous medical imaging can allow your doctor to track the progression of disease or resolve a question of anatomy, making further medical imaging unnecessary. It may also reduce the potential for an unnecessary scan – when a recent scan would provide sufficient information for patient management. Always bring past medical imaging to your doctor's visit.

If the benefit of an imaging test exceeds its risks, then it is warranted regardless of whether or not the person has had prior medical imaging radiation exposures.1-3

What is the risk?

Studies on radiation and cancer have estimated that the risks are relatively small. For instance, a UK study estimated that for every 10,000 head CT scans done before the age of 10, there was 1 extra case each of leukaemia and brain tumour 10 years after the first exposure. People who had greater exposures to radiation had a higher risk.

Similar findings were reported in an Australian study investigating the risk of any cancer after a CT scan in childhood or adolescence (up to age 19). One extra case of cancer has so far been estimated for every 1800 CT scans, about 10 years after exposure. The risk was highest after exposures in children younger than 5, and increased with each additional CT scan.

The benefit of a high-radiation scan needs to be weighed against this risk, as in the headache example below.

The findings from these studies are based on imaging practice and doses of radiation that may not reflect current practice and doses used in Australia today. Imaging technology and practice is improving all the time. Several other international studies into the risks of CT scans for children and young adults are underway.

Investigating headache — weighing up the risks and benefits

Most headaches can be diagnosed on the basis of a detailed medical history. Imaging such as MRI or CT scans rarely provide further information that will help a diagnosis, unless there is a reason to think that the cause of headache might be serious.

If a doctor thinks your child's headache is related to a recent onset of sinusitis, then they are likely to recommend delaying an imaging test — to see if it resolves with usual treatment — thereby avoiding unnecessary risks.

On the other hand, if your child had a recent head injury, then you and your doctor may decide that the risks associated with imaging — including radiation in the case of a CT scan — are less important than your child's immediate needs in diagnosing their headache.

  1. Durand, D.J., R.L. Dixon, and R.L. Morin, Utilization strategies for cumulative dose estimates: a review and rational assessment. J Am Coll Radiol, 2012. 9(7): p. 480-5.[PubMed]
  2. Eisenberg, J.D., S.O. Lewin, and P.V. Pandharipande, The fisherman's cards: how to address past and future radiation exposures in clinical decision making. AJR Am J Roentgenol, 2014. 202(2): p. 362-7. [PubMed]
  3. Walsh, C. and D. Murphy, Should the justification of medical exposures take account of radiation risks from previous examinations? Br J Radiol, 2014. 87(1037): p. 20130682. [PubMed]
General resources
  • Radiation exposure from CT scans in childhood and subsequent risk of leukaemia and brain tumours: a retrospective cohort study. Pearce M, Salotti J, Little M et al. Lancet 2012, 380:499–505 [Online]
  • Inside Radiology
  • Radiology Info