Improved simulation of Cooper ligaments in breast phantoms

Computer simulation of breast anatomy plays a crucial role in virtual clinical trials (VCTs) for preclinical optimization of breast imaging systems. Software breast phantoms provide ground truth about tissue distribution and flexibility to cover anatomical variations. We have experience with designing software phantoms based upon recursive partitioning using octrees; these phantoms simulate tissue compartments and fibrous ligaments, which contribute to the parenchymal texture. Realistic simulation critically affects the image quality and the VCT accuracy. Our simulation method may result in artifacts (bumps and dents) due to prematurely stopped partitioning of octrees. These artifacts compromise the image quality by reducing ligament smoothness and distorting parenchymal texture. In this study, we discuss the phenomenology of the artifacts and propose utilization of a spherical approximation of cubes corresponding to the octree nodes, to assess minimal and maximal distance from a cube to a median surface of the ligament. We demonstrate that the proposed technique is complementary to our earlier method proposed to improve smoothness of simulated Cooper's ligaments surface. We show that the proposed technique leads to observable changes in simulated phantom projections. The effect of the computational overhead introduced by the proposed method on the simulation time may be compensated by an efficient implementation. The proposed method may be also applied to the simulation of quasi-planar structures in other organs and (biological or non-biological) domains