ABSTRACT
Diagnostic reference levels (DRLs) are a tool for optimization of radiation dose in medical imaging. DRLs permit comparison of radiological practices among facilities. DRLs are a quality assurance and quality improvement tool, used as part of a systematic method to evaluate local practice and to help determine when investigation into facility practices is warranted. They indicate a reasonable dose for average-sized patients and provide guidance on what is achievable with good practice, rather than optimum performance.
DRLs are values of dose metrics for individual imaging examinations, most commonly determined from a survey of a number of clinical sites. The DRL value corresponds to a percentile, usually the 75th percentile, of the distribution of the observed doses in the survey. DRLs apply to groups of patients, not individual patients. Achievable doses (AD), set at the 50th percentile of the same distribution, are an additional tool for further optimization efforts.
Radiation doses at a facility above or below a DRL or AD value do not indicate that the images obtained are adequate or inadequate for a particular clinical purpose. Image quality must be assessed separately from radiation dose. Image quality that is inadequate is as bad as high patient radiation doses: when image quality is inadequate for the clinical purpose, the administered radiation provides no clinical benefit.
