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Sample histogram showing protocols and radiation dose levels across three fictitious hospitals

Dose Reference Levels (DRLs) or Dose Reference Ranges (DRRs) are used in medical imaging to refer to the amount of radiation dose considered to be “achievable.” the achievability must be based on the specific imaging modality, equipment and type of image to be acquired. In advanced medical imaging, a “protocol” refers to the specific directions for how to acquire an image based on the clinical indications for a given patient.

In Canada, there are no national DRLs or DRRs. There are recommended guidelines for DRLs in Safety Code 35, published by Health Canada. The DRLs, however, are not part of the Diagnostic Accreditation Program or DAP. In the US there are also no mandated DRLs. In the UK, national DRLs have been in place for nearly 2 decades. The UK DRLs are referenced in the Ionising Radiation (Medical Exposure) Regulations or “IRMER” pronounced “IRMA.” Recently, the National Council on Radiation Protection in the US published Report No. 172: Reference Levels and Achievable Doses in Medical and Dental Imaging: Recommendations for the United States. These are the radiation reference levels that are in use at St. Michael’s Hospital. We believe, however, that the best way to determine dose reference levels are through the use of population-based data that is regional; that is, through the aggregation of radiation metadata in Ontario we will be able to learn what our peers, operating in the Canadian healthcare context are able to achieve. There are many reasons why these may be different than the achievable doses in the US or in the UK.