Integration of a dose-voxel kernel (DVK) convolution method for voxel-based dosimetry in Particle and Heavy Ion Transport code System (PHITS)

Tatu, S. S.*; 佐藤 達彦   ; 古田 琢哉   ; Wong, Y. H.*; Kasbollah, A.*; Suppiah, S.*; Yeong, C. H.*

Tatu, S. S.*; Sato, Tatsuhiko; Furuta, Takuya; Wong, Y. H.*; Kasbollah, A.*; Suppiah, S.*; Yeong, C. H.*

Dose-voxel kernel (DVK) convolution is a practical, physics-based method for voxel-level absorbed dose estimation from nuclear imaging activity maps. We developed and integrated a DVK convolution algorithm into PHITS and evaluated it using five post-radioembolization Y SPECT/CT and PET/CT datasets converted with RT-PHITS. DVK tables were generated for 24 human tissue materials based on CT-derived voxel information, and dose rates were computed by sampling each source voxel once and applying DVK convolution. DVK produced spatial dose distributions consistent with conventional PHITS Monte Carlo (MC) simulations, with mean DVK-MC differences of -1% for both SPECT/CT and PET/CT, while reducing computation time from 36~min (MC) to 40~s. Relative to commercial LDM-based (SPECT) and VSV-based (PET) dosimetry, DVK showed mean differences of 9.7% and -0.1%, respectively, supporting further validation in clinical radiopharmaceutical therapy workflows.