Elaboration of New NDRLs as Part of Third National Patient Dose Survey in Diagnostic Radiology in Bulgaria

Purpose: The aim of this research is to elaborate an update of National Diagnostic Reference Levels (NDRLs) in Bulgaria, as required by National and International legislation. Methods and Materials: Special questionnaires and methodology instructions for submission of required data were distributed to all hospitals in the country. Patient dose records and corresponding technical data were delivered from medical institutions via following three methods: by e-mail, by specialized on-line system, or by paper. A national patient dose database build on MS Access was elaborated and employed for storing, processing and analysing of the collected data. Results: More than 10,500 patient dose records on more than 190 X-ray systems from over 90 health establishments have been collected and analysed. New national DRLs were elaborated and proposed for: Chest PA, Pelvis AP, Abdomen AP, Thoracic Spine AP, Thoracic Spine Lat, Lumbar Spine AP, Lumbar Spine Lat, Skull AP, Scull Lat, Barium meal, Barium enema, Coronary Angiography and Percutaneous Coronary Intervention—in terms of KAP; for Computed Tomography (CT) of Head, Abdomen and Lumbar Spine—in terms of CTDIw and DLP; for Mammography—in terms of ESAK and AGD. Conclusion: The new DRL values obtained are proposed as NDRLs for the country. Most are comparable with other European NDRLs with a few exceptions only. Those exceptions are most probably related to actual optimization in existing radiology practices.