The survey of local diagnostic reference levels (DRLs) for administered activity in diagnostic nuclear medicine at Rajavithi Hospital

Abstract

Background: Diagnostic reference levels (DRLs) is the useful tools for the radiation exposure reduction. DRLs in diagnostic nuclear medicine is referred to the administered activity to the patients. In Thailand, the national DRLs is not yet established at this moment. Therefore, this study aimed to determine the DRLs for diagnostic nuclear medicine procedure at Rajavithi Hospital. Objective: To survey and initiate the local DRLs for administered activity in Nuclear Medicine Division at Rajavithi Hospital and compare the DRLs with other countries. Methods: This was the retrospective survey data from the patients who underwent Nuclear Medicine examination in 2019 at Rajavithi Hospital. The mean, median and 75^thpercentile of the administered activities were reported. As International organization reported the value of DRL using 75^th percentile value, this survey compared the 75^th percentile value from Rajavithi Hospital with other countries and International organization. Then the percentage difference was calculated to determine the DRLs difference between Rajavithi Hospital and others. Results: For bone scan (571 females, 386 males, mean age 58.32+13.55), the DRL for ^99mTc-MDP was 858.03 MBq (23.19 mCi). The one day protocol of myocardial perfusion scan (164 females, 136 males, mean age 65.16+11.51), the DRL for ^99mTc-MIBI (rest) was 473.23 MBq (12.79 mCi) and the DRL for ^99mTc-MIBI (stress) was 1281.03 MBq (34.62 mCi). For parathyroid subtraction scan (54 females, 45 males, mean age 49.17+15.72), the DRL for ^99mTc-pertechnetate was 123.39 MBq (3.33 mCi) and for ^99mTc-MIBI was 902.98 MBq (24.40 mCi). The DRL for ^99mTc-MAG3 in renogram scan (42 females, 40 males, mean age 46.62+15.41) was 139.12 MBq (3.76 mCi). For MUGA scan (122 females, 5 males, mean age 49.97+11.28), the DRL for ^99mTc-RBC was 854.70 MBq (23.10 mCi). Lastly, for thyroid scan (137 females, 24 males, mean age 48.74+15.46), the DRL for ^99mTc-pertechnetate was 116.18 MBq (3.14 mCi). Conclusions: The percentage difference between Rajavithi local DRL and other countries was between 16-83%. The ones which were higher than other countries were ^99mTc-MIBI (stress), ^99mTc-MIBI (parathyroid) and ^99mTc-RBC (MUGA scan). Therefore, these three radiopharmaceuticals for these certain types of studies should be taken into account. However, these local DRLs of administered activities should be compared and adjusted in the future when the National DRLs of administered activities are published.