Monte Carlo Simulation of White Matter as a Composite Porous Medium

Gregory T. Baxter¹, Lawrence R. Frank¹

Sen and Basser developed a theoretical model for diffusion in white matter in the brain in the long-time limit. Their model represents white matter fascicles as coated cylinders in periodic arrays, with distinct axonal core, myelin sheath, and surrounding medium. We implement this white matter model in a Monte Carlo diffusion simulator to find results in the context of DTI. Anisotropy calculated from numerical simulations matches the theoretical model in the long-time limit, but anisotropy is significantly understated when diffusion time is short. Anisotropy is also sensitive to the concentration of spins in the myelin sheath.