Summary

  • X-ray and computed tomography (CT) scans use ionising radiation which is associated with an increased risk of cancer.
  • When selecting the most appropriate imaging test for your patient with abdominal pain, consider using a method which does not employ ionising radiation, if possible.
  • Children, adolescents and women are at increased risk of radiation-induced cancers, so imaging methods that do not employ ionising radiation (such as ultrasound or MRI [magnetic resonance imaging]) are preferred, whenever appropriate.
  • Don't delay a radiological test (CT or X-ray) that is justified by medical need.
Both computed tomography (CT) and X-ray result in exposure to ionising radiation. While it is commonly perceived that both involve a similar level of exposure – the level of radiation exposure during a CT scan is in fact much higher than for an X-ray.1

A CT scan of the abdomen exposes a patient to 50 times that of the organ radiation dose from a conventional X-ray.1

Imaging referrals which clearly state the clinical justification can help ensure the patient is not exposed to radiation unnecessarily.1,2

CT scans and cancer risk

The risks of adverse biological effects from ionising radiation are well-known – and the age-related risk of cancer from ionising radiation is much greater in children and young adults.3,4

Multiple CT scans of the abdomen and pelvis have been found to correlate with an increased incidence of leukemia and myelodysplasia, soft tissue cancers, brain cancers, and all other solid cancers apart from melanoma and thyroid cancer.5

To help avoid duplication of imaging studies, ask your patient about prior imaging results, and encourage them to bring these results to their appointment.2,6

Consider non-ionising alternatives

If possible, select imaging that does not use ionising radiation, particularly for younger patients and women of child-bearing age.2 Refer to the Western Australian Department of Health Diagnostic Imaging Pathways when deciding which imaging test to request.7

Children are more susceptible to radiation risks than adults, and have an enhanced lifetime risk of cancer mortality after exposure to radiation.3,4 It is particularly important for younger patients that non-ionising imaging methods (such as ultrasound or MRI) are chosen, if possible and appropriate.1,2

The incidence of cancer in radiation-exposed females is higher than males,4 particularly for solid cancers other than brain cancer.5 In women of child-bearing age and those who are pregnant, ultrasound is the method of choice for investigating abdominal pain.8

Don't delay imaging if medically needed

Always view the risk of radiation exposure during a medical imaging test in the context of its benefits. The cumulative dose of radiation and associated risks should not influence the risk or benefit of a given CT scan, and play no role in deciding whether or not to image a patient.9

When a CT (or other radiological test) is justified by medical need, the diagnostic information obtained will usually outweigh the risk – regardless of past, current or future risk of radiation exposure.1,9,10 If an imaging test is not performed when it is medically needed, the risks include the potential for missed diagnosis and delayed, inappropriate or lack of necessary treatment.11

References

  1. Brenner DJ and Hall EJ. Computed tomography--an increasing source of radiation exposure. N Engl J Med 2007;357:2277–84.
  2. WA Department of Health. Diagnostic Imaging Pathways. About Imaging: General Principles in Requesting Imaging Investigations. Government of Western Australia. Department of Health, 2015 (accessed 2 March 2015)
  3. Brenner D, Elliston C, Hall E, et al. Estimated risks of radiation-induced fatal cancer from pediatric CT. Am J Roentgenol 2001;176:289–96.
  4. Brady Z, Cain TM and Johnston PN. Justifying referrals for paediatric CT. Med J Aust 2012;197:95–9.
  5. Mathews JD, Forsythe AV, Brady Z, et al. 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:f2360.
  6. Hendee WR, Becker GJ, Borgstede JP, et al. Addressing overutilization in medical imaging. Radiology 2010;257:240–5.
  7. Australian Government Professional Services Review. Report to the professions. 2008–2009. (accessed 17 March 2015)
  8. Levine D. Use of ultrasound as an alternative to CT. American College of Radiology. Image Wisely. Radiation Safety in Adult Medical Imaging, 2010 (accessed 23 April 2015)
  9. Durand DJ, Dixon RL and Morin RL. Utilization strategies for cumulative dose estimates: a review and rational assessment. J Am Coll Radiol 2012;9:480–5.
  10. Eisenberg JD, Lewin SO and Pandharipande PV. The fisherman's cards: how to address past and future radiation exposures in clinical decision making. Am J Roentgenol 2014;202:362–7.
  11. 11. Royal Australian and New Zealand College of Radiologists. Computed tomography and radiation risks. Position statement. 2013 (accessed 9 April 2015)