Safety of CT scan

In light of a recent paper by Mark S Pearce et al. in The Lancet (Radiation exposure from CT scans in childhood and subsequent risk of leukaemia and brain tumours: a retrospective cohort study) early online publication, 7 June 2012, doi:10.1016/S0140-6736(12)60815-0, the following information is provided:

  1. CT is one of the most valuable medical imaging techniques when used justifiably.
  2. A number of professional organizations have provided appropriateness criteria or referral guidelines to achieve appropriate use. This website provides a link to some of these guidelines.
  3. X rays used in CT, while having tremendous benefits, can have side effects such as a potentially increased risk of cancer in later years.
  4. The risks of cancer from radiation dose imparted by a single CT scan is debated and international consensus is currently not available.
  5. The risk figures for cancer available in literature are projected, that is, “estimated cancer risks” based on risk coefficients derived from data from survivors of Hiroshima and Nagasaki primarily, with some other study groups also supporting the data.
  6. Despite a common view among international organizations that risk coefficients are also applicable at the level of radiation doses encountered in CT scanning, some groups have expressed the view that the risks are hypothetical as they are extrapolated from higher exposure down to lower exposures. Also, there have been objections that the risks from X rays may not be the same as with gamma radiation.
  7. With current knowledge, there is no controversy on carcinogenic effects for organ doses in excess of 100 mGy, which can accrue in five to 15 CT scans (such a wide range is needed as it depends upon techniques utilized and organs scanned).
  8. The controversy remains (despite common view among most international organizations) about cancer risk from a single or a few CT scans and this is where the new research published in the Lancet has importance.
  9. The new research reinforces the belief of major international organizations about cancer risks from a few CT scans. The risk is very low but appears to be real, not hypothetical.


  1. Image Gently, an alliance for radiation safety in paediatric imaging, has posted a message to parents on its website.
  2. The IAEA recommends tracking of radiological examinations a patient undergoes, in particular a child, to enable easy reference to availability of desired information from previous scans. This also helps to compare radiation doses with previous examinations and help in the detection of a scope for optimization. Recently, a Joint Position Statement on the IAEA Patient Radiation Exposure Tracking has been issued jointly with ESR, FDA, IAEA, IOMP, ISRRT, WHO and also CRCPD.
  3. There is information available on this website for patients and, in particular, for safety in computed tomography (CT).

Other links:

CT scans are an important diagnostic tool when used appropriately (American Association of Physicists in Medicine), direct link to AAPM web page 

Paediatric CT Scans Save Lives When Used Appropriately (American College of Radiology)

Improving Radiation Protection of Children Worldwide (IAEA)

Training material for free download in different areas

Poster - Building awareness in pregnancy


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