Predicting Mesoscopic Larmor Frequency Shifts in White Matter with Diffusion MRI -- A Monte-Carlo Study in axonal phantoms

TL;DR

This study uses Monte-Carlo simulations to demonstrate that diffusion MRI can measure and estimate the anisotropic mesoscopic Larmor frequency shifts caused by white matter microstructure, validating MRI's potential for microstructural characterization.

Contribution

It provides the first validation that MRI can quantify mesoscopic Larmor frequency shifts and their orientation dependence in white matter using Monte-Carlo simulations.

Findings

MRI can estimate mesoscopic Larmor frequency shifts

dMRI can determine the orientation dependence of these shifts

Monte-Carlo simulations validate the measurement approach

Abstract

This study aims to validate if MRI can measure anisotropic mesoscopic Larmor frequency shifts from white matter axonal microstructure relative to the B0 direction and if dMRI can estimate this anisotropy. Recent models describe how mesoscopic Larmor frequency shifts depend on induced magnetic fields by axons, described by an orientation distribution function. Using Monte-Carlo simulations of MRI signals in mesoscopic white matter axon substrates, we show MRI can estimate this mesoscopic frequency shift and dMRI can estimate its orientation dependence.