Towards a Standard Model of Diffusion in White Matter with Phase and Relaxation – A Monte-Carlo Study

Motivation: Improving parameter estimation for the standard model of diffusion in white matter (SM) by modelling the subsequent decay of the spin-echo of the dMRI signal. Goal(s): To numerically validate SMPR - an extension of SM incorporating orientation-dependent, susceptibility related relaxation rates and Larmor frequency shifts of the spin echo decay of the dMRI signal. Approach: To perform Monte-Carlo (MC) simulations in orientationally dispersed, non-exchanging bundles of hollow magnetized cylinders, simulate a standard PGSE signal and its spin echo decay, and compare against the SMPR model. Results: SMPR is in agreement with the MC simulations in both phase and signal magnitude. Impact: Orientation-dependent susceptibility effects may improve parameter estimation of the Standard Model of diffusion in white matter and enable rotation-free mapping of susceptibility-related parameters.