Establishment of CT diagnostic reference levels (DRLs) in Tokyo

Area of Science:

• Medical Imaging Physics
• Radiological Sciences
• Health Services Research

Background:

• Diagnostic reference levels (DRLs) are vital for optimizing radiation dose in CT scans.
• Current DRLs may not accurately represent individual facility performance or scanner capabilities.
• Factors influencing DRLs require further investigation.

Purpose of the Study:

• To investigate the impact of facility characteristics on CT radiation dose.
• To evaluate the influence of CT scanner performance on diagnostic reference levels.
• To identify key factors affecting radiation dose in clinical CT examinations.

Main Methods:

• A dose survey was conducted in 2023 involving 100 facilities and 176 CT scanners in Tokyo.
• Data from adult patients undergoing common CT protocols were analyzed for CTDIvol and DLP.
• The 75th percentile of radiation dose was defined as the Tokyo-DRL.
• Factors such as radiologist presence, technologist certification, hospital size, scanner specs, and reconstruction methods were evaluated.

Main Results:

• Tokyo-DRLs were found to be lower than national DRLs, suggesting technological and expertise advancements.
• Lower radiation doses were observed in facilities with radiologists, certified technologists, larger bed counts, wider beam widths, and advanced reconstruction techniques.
• Tube current modulation, scan sequence, and beam width were identified as significant dose-influencing factors.

Conclusions:

• Facility characteristics and CT scanner performance substantially influence radiation dose.
• Regular, detailed surveys are essential for updating DRLs to align with technological and clinical practice changes.
• Understanding these factors aids in optimizing radiation dose for patient safety and diagnostic quality.