Myelin water imaging is a quantitative neuroimaging technique that provides the myelin water fraction (MWF), a metric highly specific to myelin content, and the intra-/extra-cellular T2 (IET2), which is related to water and iron content. We coupled high-resolution data from 100 adults with gold-standard methodology to create an optimized anatomical brain template and accompanying MWF and IET2 atlases. We then used the MWF atlas to characterize how myelin content relates to demographic factors. In most brain regions, myelin content followed a quadratic pattern of increase during the third decade of life, plateau at a maximum around the fifth decade, then decrease during later decades. The ranking of mean myelin content between brain regions remained consistent across age groups. These openly available normative atlases can facilitate evaluation of myelin imaging results on an individual basis and elucidate the distribution of myelin content between brain regions and in the context of aging.

We investigated the relationship between diffusion model biomarkers and inflammatory cells, as measured by HLA-DR and CD68 histological staining for activated microglia and macrophages, after human traumatic spinal cord injury. Fractional anisotropy decreases and radial and mean diffusivity increases were strongly correlated with the presence of activated microglia and macrophages. ActiveAx-derived intra-cellular volume fraction and axon density decreased while axon diameter increased. Fiber fraction from Diffusion Basis Spectrum Imaging decreased and while hindered fraction increased in the presence of inflammation.

We investigated the correlation of inhomogeneous magnetisation transfer ratio (ihMTR), myelin water fraction (MWF) and intra/extra-cellular water geometric mean T2 (I/EW gmT2) with the distribution of inflammatory cells as measured by HLA-DR and CD68 histological staining for macrophages and activated microglia in human traumatic spinal cord injury. We found that ihMTR and MWF decreases were strongly correlated with the presence of HLA/CD68+ immune cells in white matter and both ihMTR and MWF were strongly correlated with LFB, a stain for myelin lipids. Our results demonstrate a strong link between ihMTR and MWF and inflammation.