Determination of bremsstrahlung radiation dose level of 90Y-SIRT in China: validation by practical measurement and theoretical estimation

Abstract Objective The purpose of this study is to determine the dose level of bremsstrahlung radiation in 90Y-SIRT and to estimate the dose of radiology staff. Methods A survey meter and a theoretical equation were used to measure and calculate the bremsstrahlung radiation emitted by 90Y in each stage of 90Y-SIRT, respectively. The differences between theoretical calculation and measured values were then compared. Finally, the annual exposure doses of radiology staff were estimated and analyzed. Results The dose level of 90Y bremsstrahlung radiation outside the lead shield was relatively low. For example, the dose rate were 0.19~0.26μSv·h-1·GBq-1 at 1 m from the surface of the lead pot or the lead transfer box. While it became higher when there were no lead shielding, such as 1.00~1.60μSv·h-1·GBq-1 at 1 m from the surface of the shipping vial, the acrylic V-Vial kit, the injection box or the patient. Under the condition that 200 patients each year, 3GBq for each vial of 90Y microspheres, maximum dosage of 2GBq per patient, the estimated annual effective dose of nuclear medicine technologist, interventional injection physician and ward-round physician were 2.24mSv, 1.04mSv and 0.22mSv respectively, and the annual equivalent dose of hand were 49.9mSv, 25.5mSv and 2.06mSv respectively. The maximum deviation between the calculated and measured dose of bremsstrahlung radiation was -22%. The attenuation factors of 6.4mmPb equivalent lead pot and 0.5mmPb equivalent lead apron for 90Y bremsstrahlung radiation were between 0.13 ~ 0.15 and 0.45 ~ 0.50, respectively. Conclusions In this study, the dose level of 90Y bremsstrahlung radiation was determined, and an accurate and convenient theoretical calculation method of 90Y bremsstrahlung radiation was recommended. Generally, the annual effective dose of radiology staff in 90Y-SIRT will not exceed the hospital management target value of 5 mSv in China. Wearing personal radiation protective equipment during the injection stage in90Y-SIRT and covering the patient's injection sites with lead apron can achieve approximately 50% dose reduction for radiology staff.