Ionising radiation in infancy and adult cognitive function

BMJ 2004; 328 doi: https://doi.org/10.1136/bmj.328.7439.581-a (Published 04 March 2004) Cite this as: BMJ 2004;328:581

Protocols for computed tomography must be optimised

  1. Jill Meara, deputy director (jill.meara{at}nrpb.org),
  2. Gerry Kendall, head, population exposure department,
  3. Colin Muirhead, group leader, epidemiology,
  4. Barry Wall, group leader, medical dosimetry
  1. National Radiological Protection Board, Chilton, Didcot, Oxfordshire OX11 0RQ

    EDITOR—Hall et al report adverse effects on adult cognitive function among male patients treated with radiation for skin haemangioma during infancy.1 The evidence for effects was strongest among those receiving the highest doses.

    It is unclear whether there was a dose threshold below which no effects occurred. This study of a sizeable cohort seems to be well conducted with minimal risk of bias. A group of patients with haemangioma was compared by brain dose rather than with an external group. Consequently confounding would seem plausible only if the severity of the clinical condition affected cognitive function and was correlated with brain dose.

    Other studies have shown adverse effects of radiation on intellectual development, although interpretation is complicated because some studies used higher doses from exposures in utero or may have been subject to confounding.

    Good radiation protection practice (reducing unnecessary exposures and minimising radiation doses) controls well established risks, largely of radiation induced cancers. Computed tomography entails higher doses than plain radiography. Computed tomography of the head is a first line examination only for children whose symptoms imply notable brain injury.2

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    Nevertheless, unless the protocol for computed tomography scanning is adjusted for infants, the brain dose (as opposed to the “effective dose,” which is integrated across the whole body) could exceed 100 mGy, within the upper range of doses in the study by Hall et al. This reinforces the need for optimising protocols for computed tomography, minimising the dose to the patient and restricting examinations to infants with clear clinical indications.


    • Competing interests All authors work for the National Radiological Protection Board, which has a statutory duty to advise on protecting the public from the harmful effects of radiation. The original electronic response also appears on the website of the National Radiological Protection Board.


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