This article describes the system of regulation and practical guidance that has been developed in the UK for implementing the requirement in the EC Medical Exposure Directive that all Member States shall promote the establishment and use of diagnostic reference levels (DRLs) for medical X-ray examinations. In particular, it describes the role of two national patient dose databases maintained by NRPB, which provide important sources of information on which formally adopted numerical values for 'national DRLs' will be based. One database deals with radiographic and fluoroscopic examinations and the recommended 'national reference doses' from the latest review of this database are discussed. The other database deals specifically with computed tomography (CT) examinations, which now account for 50% of the collective dose to the UK population from all medical X rays and are consequently of particular radiation protection concern. The first analysis of this CT database is still underway, but some encouraging indications of a reduction in patient dose for some CT examinations are reported. Progress in formally adopting numerical values for 'national DRLs', as required by the UK regulations, and the provision of authoritative guidance on the implementation of DRLs at the local level, are also discussed.
