External radiation spatial distribution and safety assessment of yttrium-90 resin microsphere selective hepatic radioembolization therapy

Purpose: This study investigated the spatial distribution pattern of external radiation dose rates from patients treated with 90Y resin microspheres and evaluated the potential radiation exposure to other individuals. Methods: External radiation dose rates from 15 patients were measured post-therapy. A curve fit was performed using MATLAB to verify adherence to the inverse square law. Association between dose rate and administered activity or body mass index (BMI)-adjusted administered activity was analyzed using linear regression and correlation. The equations were fitted to predict the dose rate based on administered activity and BMI. Total radiation doses to exposed individuals were estimated based on interaction patterns. Results: The average dose rates were 84.1 μSv/h at contact, decreasing to 8.0 μSv/h at 0.3 m, 4.2 μSv/h at 0.5 m, 1.7 μSv/h at 1 m, and 0.7 μSv/h at 2 m. Beyond 0.5 m, the dose rate varied inversely with the square of the distance, allowing the patient to be treated as a point source. BMI-adjusted administered activity showed better correlation with dose rates than administered activity alone, suggesting the dose rate was influenced by varying levels of attenuation by the patient’s abdomen. The equations for estimating the spatial distribution of initial dose rate were fitted using administered activity/BMI2 as a patient-specific parameter. Moreover, the estimated total radiation doses to exposed family members and clinical staff in this study were well below the dose constraints. However, when discharged at 6 h after treatment or hospitalized for 5 days, estimated total radiation doses to co-workers or wardmates from a patient administered 3.06 GBq exceeded the 0.1-mSv public dose constraint. Conclusion: For patients receiving more than 3 GBq 90Y microspheres, dose-rate measurement and individualized radiation protection protocols are essential. The proposed formulas for dose-rate spatial distribution estimation may simplify clinical monitoring and help guide personalized protection.