Geant4-based Model of a Mouse Injected with Gold Nanoparticles for X-Ray Tomography Simulation Studies

The motivation of this study was to develop a Geant4-based novel three dimensional (3D) digital mouse model derived from in vivo cone-beam computed tomography (CBCT) images of a mouse injected with gold nanoparticles (GNPs) for x-ray tomography simulation studies. Pixel-by-pixel CT numbers from axial CBCT images of a mouse, obtained before and after injecting GNPs, were converted into material densities and then transformed into identical 3D voxels using a custom Geant4 application. The consecutive materialized slices were then stacked along the longitudinal axis to build the whole-body mouse models. The first mouse model showed no GNPs inside any organs of interest or the skeleton, whereas the second model showed the actual GNP biodistributions inside the kidneys along with the anatomical features. The applicability of the mouse models for x-ray imaging was investigated by a whole-body CBCT and x-ray fluorescence computed tomography (XFCT) Monte Carlo (MC) simulations. The current investigation showed the feasibility of developing digital mouse models using CBCT images of a mouse injected with GNPs and their application to simulation studies of preclinical CBCT or XFCT or multimodal CBCT+XFCT imaging.