Risk and benefit in paediatric radiology.

An investigation requiring the use of ionising radiation can be justified by showing that its benefits are likely to exceed its risks. The risks can be estimated from the effective dose by using the system recommended by the International Commission on Radiological Protection. The benefits of investigations in paediatric radiology are currently unquantified. We can assume that some tests have potential benefits so large that further evaluation is unnecessary. Others have a maximum potential benefit so low that they can be discarded. For most investigations, however, research into the magnitude of benefit to the patient is required in order to establish that it is greater than the magnitude of the radiation risk.