Establishment of National Diagnostic Reference Levels 2025 for nuclear medicine in Japan

Diagnostic reference levels (DRLs) are practical benchmarks for optimizing patient radiation exposure in medical imaging. In Japan, national DRLs, including those for nuclear medicine together and other radiological procedures, were first established in 2015 and revised in 2020. In this study, we revised the DRL values of nuclear medicine for the establishment of DRLs2025, based on data collected from institutions nationwide throughout Japan. Data were collected via an online survey from facilities performing nuclear medicine procedures, including SPECT, PET, and hybrid CT imaging. Information on dose activity of the administered radiopharmaceuticals and CT parameters (CTDIvol and DLP) were collected. DRL values were determined through analysis of the submitted data, supplemented by panel discussions among experts taking into account the clinical appropriateness of the values and various technological factors. Overall, the newly established DRLs2025 demonstrated a decreasing trend in administered radiopharmaceutical activities, CTDIvol, and DLP compared with the previous surveys. This trend reflects ongoing efforts toward the optimization of radiation exposure and radiopharmaceutical dose reduction, likely driven by the introduction of image reconstruction methods based on newer technologies. However, substantial interfacility variations were observed, particularly in the CT parameters, suggesting disparities in equipment, imaging protocols, and the balance between image quality and radiation dose. The establishment of DRLs2025 underscores continued progress in optimizing radiation exposure in nuclear medicine practice in Japan. Although issues regarding data variability and quality remain, DRLs continue to be a key tool in radiation protection and quality assurance. Ongoing efforts to improve data collection systems and to align procedures with international standards are essential for the future refinement of DRLs.