Assessment of the structural complexity of diffusion MRI voxels using 3D electron microscopy in the rat brain

Validation and interpretation of diffusion magnetic resonance imaging (dMRI) requires detailed understanding the actual microstructure restricting water molecules. In this study, we used serial block-face scanning electron microscopy (SBEM), a three-dimensional (3D-EM) technique, to image seven white grey matter volumes in rat brain. SBEM shows excellent contrast cellular membranes, which are major components tissue. Additionally, performed 3D structure tensor (3D-ST) analysis on parameterised resulting orientation distributions using Watson angular central Gaussian (ACG) probability as well spherical harmonic (SH) decomposition. We analysed how these parameterisations described underlying compared their dispersion with corresponding parameters from two dMRI methods, neurite density (NODDI) constrained deconvolution (CSD). ACG SH decomposition captured 3D-ST distributions, but better represented due its ability model asymmetric dispersion. The corresponded volumes, correspondence was less evident more complex matter. also revealed that were often not axially symmetric, property neatly by distribution. Overall, barriers intricate detail, combined parameterisation, provides step forward toward interpreting validating signals brain tissue microstructure.