Image-based canine skeletal model for bone microdosimetry in the UFDog phantom

Objectives The purpose of this study was to construct a detailed skeletal model for a canine phantom recently developed for pre-clinical nuclear medicine dosimetry [J Nucl Med 49 (3) 446-452 (2008)].

Methods Skeletal samples were acquired from an average-weight hound and subjected to microCT imaging. CT-based models of whole canine bones were coupled to microCT images of trabecular spongiosa under Paired-Image Radiation Transport (PIRT). Five source regions were considered for electron and beta-particle dosimetry: Active and Inactive Trabecular Marrow (TAM, TIM), Cortical Bone Volume (CBV), Trabecular Bone Volume and Surface (TBV, TBS). The two tissues used as targets were the TAM and the TAM₅₀. TAM was used as a surrogate for the hematopoietic cells. TAM₅₀ represents the TAM that is within 50 microns of the bone surfaces in spongiosa.

Results A complete set of AFs and SAFs were calculated for all skeletal sites. AF values and their energy dependence vary strongly with source-target combination. For example, the AF values from TAM self-irradiation start approximately at unity at very low energies, and then decrease with increasing energy, whereas AF values for a TAM source and a TAM₅₀ target start at approximately 0.65.

Conclusions The data presented will allow researchers the opportunity to make accurate assessments of skeletal tissue dose in pre-clinical radionuclide therapy studies using the canine animal model.

Research Support Work supported by NCI Grant F31 CA130165.