SU‐GG‐AUD‐03: The Development and Validation of An Image‐Based Dosimetry System for 90Y Microspheres Used to Treat Hepatic Tumors

Abstract

Purpose: To develop and experimentally validate an image‐based dosimetry system for determining the three‐dimensional (3D) dose distribution from microspheres used to treat hepatic tumors. Method and Materials: A rapid, efficient, and stable batch technique was used to label yttrium‐loaded microspheres with . These ‐labeled microspheres served as surrogates for ‐labeled microspheres. and microspheres were coinjected into a gel‐based phantom and the activity distribution was determined using a GE Discovery LS PET/CT scanner. The activity distribution was converted from to by applying a precise activity ratio, which was determined using germanium detection and a low uncertainty positron branching ratio. To calculate the dose, the image data was convolved with a dose point kernel using 3D‐ID software. This dose was compared to the dose measured in the central plane using HD‐810 radiochromic film and a new film protocol. The film protocol and the gel‐based phantom were validated using a single source seed. The film was calibrated using two NIST‐traceable ophthalmic applicators and was analyzed using a flatbed scanner in reflective mode. Additionally, the image‐based dose to the entire gel phantom was compared to a Monte Carlo‐derived dose. Results: The image‐based (3D‐ID) dose in the central plane was 90.20 Gy ± 6% and the film measured dose was 90.64 Gy ± 5%. A mean phantom dose of 74.30 Gy ± 6% and 74.70 Gy ± 2% was determined using 3D‐ID and Monte Carlo, respectively. Overall, these results agreed to within 0.5%. The image‐based in vivo dose volume histogram (DVH) for this study was in excellent agreement with the film measured DVH. Conclusion: Through the implementation of ‐labeled microspheres, a precise non‐destructive assay of , and a validated film protocol, a new image‐based dosimetry system for microspheres was experimentally validated.