Including mesoscopic frequency shifts from fibrous structure of white matter improves accuracy of QSM

Quantitative Susceptibility Mapping (QSM) is a highly utilized MRI modality for mapping tissue susceptibility. However, a limitation of QSM is disregarding mesoscopic field effects associated with WM microstructure and anisotropic susceptibility. Here we present a minimal extension of QSM by including frequency shifts due to the fibrous WM microstructure, while still neglecting susceptibility anisotropy and WM spherical inclusions modelling iron complexes. We find that this step already improves the accuracy of QSM as it is shown by comparison with conventional QSM using a digital phantom that includes microstructural frequency shifts from multiple sources.