Modeling “Textured” Bones in Virtual Human Phantoms

Abstract

The purpose of this study 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 (XCAT). Cortical bone was modeled by 3D morphological erosion of XCAT homogenously defined bones with an average thickness measured from the 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 3D power spectrum of the anatomical images exhibited a power law behavior (R2 = 0.84), as expected in fractal and porous textures. The proposed texture synthesis algorithm was able to synthesize textures emulating real anatomical images, with the simulated CT images with the prototyped bones were more realistic than those simulated with the original XCAT models. Incorporating intra-organ 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.

Virtual clinical trials in medical imaging: a review

“…[43][44][45] Similar approaches have been implemented to incorporate intraorgan structures for other organs such as the liver, [46][47][48] brain, [49][50][51] heart, [52][53][54] and bones. [55][56][57] Recently, some studies have showed that deep learning approaches, such as generative adversarial network (GAN) models, can synthesize images that have similar visual and statistical features of a set of training input data. 58,59 These techniques can also be utilized for the purpose of modeling intraorgan heterogeneities within the organs and structures of computational phantoms, particularly for the parenchymal regions where organs usually have "textural" appearances.…”

“…[305][306][307] Abadi et al 141,308 characterized the noise texture across filtered back projection and iterative reconstruction algorithms. In this study, an XCAT phantom 41,55 was imaged 50 times using a validated CT simulator, setup to mimic the parameters and settings of a specific scanner model (Siemens Definition Flash). The simulated images were reconstructed with both filtered backprojection and iterative reconstruction algorithms using a commercial software.…”

“… 43 – 45 Similar approaches have been implemented to incorporate intraorgan structures for other organs such as the liver, 46 – 48 brain, 49 – 51 heart, 52 – 54 and bones. 55 – 57 …”

DukeSim: A Realistic, Rapid, and Scanner-Specific Simulation Framework in Computed Tomography

“…A textured XCAT phantom [13], [14], [16] was imaged 50 times using DukeSim, based on the properties of a commercial scanner (Somatom Definition Flash; Siemens Healthcare) 120 kV and a pitch of 1.0. Projection images were reconstructed using a commercial reconstruction software (Siemens ReconCT) with filtered backprojection (FBP, kernel of B31f) and iterative (SAFIRE, kernel of I31f) algorithms.…”

“…On the patient side, there have been extensive efforts in developing populations of anthropomorphic phantoms that model highly detailed organ anatomies [1]- [7] with intraorgan heterogeneities in the breast [8]- [12], lungs [13], [14], liver [15], and bones [16].…”