National reference doses

NRPB had recommended national reference doses for common diagnostic x-ray examinations since 1990; these recommendations have been adopted by HPA. They were originally based on a national patient dose survey conducted by NRPB in the mid-1980s and published in Documents of the NRPB, Volume 1, No 3. They are now based on the five-yearly reviews of the NPDD.

Typical patient doses for the same type of x-ray examination are seen to vary considerably from hospital to hospital and reference doses are intended to give an indication of unusually high values. They are therefore set at about the third quartile value of the distribution of typical doses seen in the NPDD from hospitals all over the country. Hospitals found to be consistently exceeding the national reference doses should investigate the reasons for using such abnormally high doses and, if they cannot be clinically justified, should carry out corrective action to bring their doses more into line with the majority.

Guidance on the purpose and means of implementing national reference doses had also been published by NRPB in collaboration with the appropriate professional bodies in Documents of NRPB, Volume 4, No 2 and Volume 10, No 1.

The Ionising Radiation (Medical Exposure) Regulations enacted in 2000 (IR(ME)R 2000), require all British hospitals to implement 'diagnostic reference levels' (DRLs). For this regulatory purpose, 'national DRLs' are to be promulgated by a special Department of Health DRL Working Party. The Department of Health has agreed that the NRPB recommended 'national reference doses' will be a major source of input when setting and reviewing 'national DRLs'.

The national reference doses recommended by NRPB in the 2000 review of the NPDD (NRPB-W14) are shown in the following three tables.

Last reviewed: 3 December 2009