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

This study investigated the spatial distribution pattern of external radiation dose rates in patients treated with yttrium-90 (⁹⁰Y) resin microspheres and evaluated the potential radiation exposure to other individuals. External radiation dose rates from 15 patients were measured following therapy. A curve fit was performed using MATLAB to verify adherence to the inverse square law. The association between dose rate and administered activity or body mass index (BMI)-adjusted administered activity was analysed using linear regression and correlation. The equations were fitted to predict the dose rate based on the administered activity and BMI. Total radiation doses to exposed individuals were estimated based on interaction patterns. The average dose rates were 84.1μSv h^-1at contact, decreasing to 8.0μSv h^-1at 0.3 m, 4.2μSv h^-1at 0.5 m, 1.7μSv h^-1at 1 m, and 0.7μSv h^-1at 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. The BMI-adjusted administered activity displayed 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 the initial dose rate were fitted using administered activity/BMI²as a patient-specific parameter. Moreover, the estimated total radiation doses to exposed family members and clinical staff in this study were well below the dosage constraints. However, when discharged at 6 h after treatment or hospitalised for 5 d, the estimated total radiation doses to coworkers or wardmates from a patient administered at 3.06 GBq exceeded the 0.1 mSv public dose constraint. Dose rate measurements and individualised radiation protection protocols are essential for patients receiving more than 3 GBq⁹⁰Y microspheres. The proposed formulas for dose rate spatial distribution estimation may simplify clinical monitoring and help guide personalised protection.