Modeling “Textured” Bones in Virtual Human Phantoms

The purpose of this paper was to develop detailed and realistic models of the cortical and trabecular bones in the spine, ribs, and sternum and incorporate them into the library of virtual human phantoms [extended cardiac-torso (XCAT)]. Cortical bone was modeled by 3-D morphological erosion of XCAT homogenously defined bones with an average thickness measured from the computed tomography (CT) dataset upon which each individual XCAT phantom was based. The trabecular texture was modeled using a power law synthesis algorithm, where the parameters were tuned using high-resolution anatomical images of the Human Visible Female. The synthesized bone textures were added into the XCAT phantoms. To qualitatively evaluate the improved realism of the bone modeling, CT simulations of the XCAT phantoms were acquired with and without the textured bone modeling. The 3-D power spectrum of the anatomical images exhibited a power law behavior ( $\text{R}^{2} = {0.84}$ ), as expected in fractal and porous textures. The proposed texture synthesis algorithm was able to synthesize textures emulating real anatomical images, where the simulated CT images with the prototyped bones were more realistic than those simulated with the original XCAT models. Incorporating intraorgan structures, the “textured” phantoms are envisioned to be used to conduct virtual clinical trials in the context of medical imaging in cases, where the actual trials are infeasible due to the lack of ground truth, cost, or potential risks to the patients.