Visualization of iron and myelin cytoarchitecture in postmortem human brain using sub-millimeter multi-orientation chi- separation

Motivation: While high-resolution quantitative susceptibility mapping (QSM) reveals unprecedented anatomical cytoarchitectures, delineation of certain substructures may be limited in regions containing both iron and myelin. Goal(s): To demonstrate iron and myelin-specific anatomy inside human brain using sub-millimeter susceptibility source-separation (chi-separation). Approach: Sub-millimeter multi-orientation QSM and chi-separation were obtained on postmortem human hemibrain at 7T. Capabilities of QSM, χpara and χdia contrasts for delineating neuroanatomy were compared. Results: While iron-rich substructures like line of Gennari can be readily identified in QSM, χdia helps reveal small fibers including striatal tracts, perforant pathway and fibers in cortical/subthalamic area. Impact: Sub-millimeter susceptibility source separation images can delineate neuroanatomical substructures in the human brain with increasing specificity to iron or myelin related cytoarchitecture.