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Diagnostic reference levels (DRLs) are an optimisation tool for medical imaging procedures using ionising radiation. They give an indication of the expected radiation dose received by an average-sized patient undergoing a given imaging procedure. Comparison of typical (median) exposure levels for common imaging procedures with DRLs helps imaging facilities identify procedures that may be amenable to further optimisation. Undertaking comparisons with published DRLs is a requirement for medical imaging facilities under the Code for Radiation Protection in Medical Exposure and for their access to Medicare rebates under the Diagnostic Imaging Accreditation Scheme (DIAS). The Australian Radiation Protection and Nuclear Safety Agency has created the National Diagnostic Reference Level Service to facilitate the collection of data for the establishment of national DRLs in Australia and to assist imaging facilities in comparing their typical doses with the national DRLs. National DRLs have been established in computed tomography, nuclear medicine, and for image-guided and interventional procedures. DRLs must be subject to ongoing review and revision by the national authority to ensure they reflect current practice. This ongoing cycle of assessment and review helps to ensure that the ratio of benefit to risk for patients is maximised. [ABSTRACT FROM AUTHOR]

Introduction: In 2018, ARPANSA published updated national DRLs for adult CT, which were first published in 2012, and augmented the national DRL categories. This paper presents the updated national DRLs and describes the process by which they were produced. Methods: Examine patient survey data submitted to the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) National Diagnostic Reference Level Service (NDRLS). Determine the quartiles of the distributions of median survey dose metrics with categorisation by procedure type. Engage a liaison panel representing the radiology professions to review procedure categories and recommend revised national DRLs. The revised NDRL procedure categories are: head (non‐contrast brain (trauma/headache)), cervical spine (Non‐contrast (trauma)), soft‐tissue neck (post‐contrast (oncology)), chest (post‐contrast (oncology)), abdomen–pelvis (post‐contrast (oncology)), kidney–ureter–bladder (non‐contrast (suspected renal colic)), chest–abdomen–pelvis (post‐contrast (oncology)) and lumbar spine (non‐contrast (degenerative pain)). Results: The existing six procedure categories were revised and refined. Updated Australian national diagnostic reference levels for adult CT were recommended and endorsed for eight procedure categories: head (52 mGy/880 mGycm), cervical spine (23 mGy/470 mGycm),soft‐tissue neck (17 mGy/450 mGycm), chest (10 mGy/390 mGycm), abdomen–pelvis (13 mGy/600 mGycm), kidney–ureter–bladder (13 mGy/600 mGycm), chest–abdomen–pelvis (11 mGy/940 mGycm) and lumbar spine (26 mGy/670 mGycm). The updated national DRLs are between 12 and 26% lower than the previous DRLs for dose‐length product and between 13 and 63% lower for volume computed tomography dose index. Conclusions: Australian national DRLs for adult CT have been reviewed and revised. The revised national DRLs are lower, better reflecting current practice among imaging facilities in Australia. The revised Australian national DRLs are similar to those in other developed countries. [ABSTRACT FROM AUTHOR]