National collection of local diagnostic reference levels in Norway and their role in optimization of X-ray examinations

摘要

The concept of diagnostic reference levels (DRLs) is recognised as an efficient and powerful tool inoptimization of diagnostic X-ray examinations. Norway was one of the pioneer countries in establishing nationalDRLs, but focus on implementation and use of DRLs locally at the clinics in optimization purposes has beenabsent until now. The aim of this study was to map the dose levels and optimization potentials by carrying out anational collection of local DRLs. Totally 40 health care enterprises (HCEs) representing 104 individual clinicswere asked to report local DRLs for eleven conventional X-ray examinations (including mammography) and nineCT-examinations. The response rate from the clinics was 69% and resulted in 539 individual reported local DRLsin total. Large variations in local DRLs were observed between different clinics for all examination types, rangingfrom a factor of 3.3 to 61 for conventional coronary angiography and lumbar spine, respectively. Local DRLsexceeding the current national DRLs were observed for all examination types except for conventional coronaryangiography. The 75th percentile of the collected local DRLs indicates a need for a downward revision of thenational DRLs by 20-60%. A recalculation of the collective effective dose (CED) of 1.1 mSv from 2002 based onthe updated dose data resulted in a reduction of the CED by 17%. The impact on patient dose by replacing someconventional X-ray examinations (urography, colon, coronary angiography) with CT-examinations is also brieflydiscussed.