Within gray and white mater R2* variations correlate histochemical iron stain of the human brain

The magnitude and phase images derived from high resolution T2* weighted MRI at high field strength have been used to reveal laminar contrast in the gray (GM) matter and fiber bundle-like structure in the white matter (WM) of the human brain [1,2]. Interestingly, this contrast is quite variable within cortical gray matter and within subcortical areas near the border between GM and white matter. This has been attributed to variations in magnetic susceptibility, possibly due to iron and myelin. A recent iron extraction study of the visual cortex suggests that non-heme iron is the primary source of cortical laminar susceptibility contrast [3]. In this study, we performed correlative R2* mapping and histology in postmortem human visual area tissue to assess the contribution of iron and myelin in the R2* variations within GM and WM.