Prospective study of direct radiation exposure measurements for family members living with patients with prostate ¹²⁵I seed implantation: Evidence of radiation safety

Purpose: To broaden the current understanding of radiation exposure and risk and to provide concrete evidence of radiation safety related to ¹²⁵I seed implantation. Methods and Materials: Direct radiation exposure measurements were obtained from dosimeters provided to 25 patients who underwent ¹²⁵I seed implantation, along with their family members. The estimated lifetime exposure dose and the precaution time for holding children near the patient's chest were calculated in two study periods. Results: During the first and second study period, the mean estimated lifetime exposure doses were, respectively, 7.61 (range: 0.45, 20.21) mSv and 6.84 (range: 0.41, 19.20) mSv for patients, and 0.19 (range: 0.02, 0.54) mSv and 0.25 (range: 0.04, 1.00) mSv for family members. The mean ratios of first and second period measurements were 1.05 (range: 0.44, 3.18) for patients and 1.82 (range: 0.21, 7.04) for family members. The corresponding absolute differences between first and second period measurements were -0.77 (range: -11.40, 7.63) mSv and 0.06 (range: -0.26, 0.79) mSv, respectively. Assuming a dose limit of 1 mSv, the precaution times for holding a child every day of the first and second periods were 250.9 (range: 71.3, 849.4) min and 275.2 (range: 75.0, 883.4) min, respectively. Assuming a dose limit of 0.5 mSv, the corresponding precaution times were 179.0 (range: 35.6, 811.5) min and 178.9 (range: 37.5, 1131.8) min, respectively. Conclusions: Our study demonstrated low radiation exposures to family members of patients undergoing ¹²⁵I prostate implantation. It was clear that ¹²⁵I seed implantation did not pose a threat to the safety of family members.