Can we detect the effect of spines, leaflets and beads on the diffusion of brain intracellular metabolites? A confrontation between high b-values and high-frequencies diffusion-weighted MRS in the mouse brain in vivo.

Prior models used to clarify which aspects of tissue microstructure mostly affect intracellular diffusion and corresponding diffusion-weighted magnetic resonance signal have focused on relatively simple geometrical descriptions of the cellular microenvironment (spheres, randomly oriented cylinders, etc...), neglecting finer morphological details which may have an important role. Neuritis may exhibit beading; some types of neurons present high density of spines; and astrocytes and macroglial cells processes present leaflets, which may all slow impact the diffusion process. Here we use numerical simulations to interpret metabolites diffusion-weighted MRS data in the mouse brain in terms of such fine secondary structures.