Development of Diagnostic Reference Levels for Nuclear Medicine in Brazil: Insights from a University Hospital

Diagnostic reference levels (DRLs) are essential for optimizing radiologic practices and ensuring patient safety. This study aimed to establish typical DRLs for nuclear medicine (NM) procedures performed at a Brazilian public university hospital. Methods: A retrospective analysis of 2,609 patient records from 13 routine NM procedures was conducted. Administered activities were analyzed to determine typical DRLs using the median (50th percentile), and data dispersion was evaluated using the interquartile range. Effective doses were estimated on the basis of International Commission on Radiological Protection dose coefficients. Results: For most procedures, typical DRLs were below the national reference levels, indicating optimized practices. Two procedures (static renal and parathyroid scintigraphy) had DRLs exceeding national values because of specific protocol adjustments. Elevated variability was observed in myocardial perfusion (1-d protocol) and lung perfusion procedures, attributed to clinical workflow constraints and individualized adjustments based on patient condition or clinical indications. Dosimetric estimates confirmed that all procedures were within safe exposure limits. Conclusion: This study reinforces the importance of establishing typical DRLs as a foundation for national DRL updates. The results provide valuable insights for optimizing NM practices in Brazil, supporting radiologic protection, and improving patient safety.