Time dependent diffusion and kurtosis of human brain metabolites

This work demonstrates that metabolites diffusion and kurtosis time-dependence can be measured in vivo in the human brain using Diffusion-Weighted MR Spectroscopy (DW-MRS) and ultra-strong gradients. At short diffusion-times, DW-MRS is sensitive to cytoplasmic viscosity and short-range structures; at long diffusion-times to long-range structures. We show that modeling the diffusion-time dependence of intracellular and cell-type specific metabolites can be used to infer brain cell morphology and recover fiber radii consistent with healthy human brain histology. Furthermore, we show that water diffusion at long diffusion-times is affected by exchange between intra- and extracellular compartment, which poses challenges for microstructural modeling.