Source of Support: None, Conflict of Interest: None
The large potential for patient dose reduction in the UK became evident when a nation patient dose survey conducted by NRPB in the early 1980s, revealed wide variations in practice. NRPB then collaborated with the professional organisations of radiologists, radiographers and medical physicists to produce advisory documents on patient dose reduction and measurement in diagnostic radiology. They included guideline reference doses for common types of examination against which X-ray departments could compare their performance. Following this advice, the results of over 50,000 patient dose measurements made at 375 hospitals were sent to. NRPB's national database by the end of 1995. The mean doses for each type of examination were seen to have fallen by about 30% since the earlier survey and only about 10% of hospitals still exceed the reference dose levels, indicating a substantial saving in the collective dose to the population from medical X-rays. However, the rapid increase in the use of high-dose computed tomography (CT) over the past decade has led to an increase in the collective dose, which will more than overweigh the reduction observed for conventional X-ray examinations. Correct application of the ICRP radiation protection principles of justification and optimisation does not necessarily require a lowering of the collective dose from such a potentially beneficial use of ionising radiation as diagnostic radiology. To maximise the margin of benefit over harm may require greater provision of diagnostic radiology services in appropriate areas resulting in a higher collective dose but a higher net health benefit to the population.