Figure 2.

Scanning SAXS of the 25μm-thick mouse brain section, and comparison with dMRI. A) Diffraction patterns from the section points indicated in (B). Background signal (panel 1) is featureless, whereas signal from white matter regions (panels 2-5) displays characteristic maxima, along the repeat structure of the myelin sheath and perpendicular to the fiber orientation. Gray matter areas displayed very little or no peak (panel 6), with the exception of the molecular layer (panel 7), where faint peaks were consistently detected. B) Color-coded map depicting microstructure orientation of the brain section, at 25μm resolution. Color hue indicates the main 2D orientation, interpreted by the inset colorwheel, whereas color intensity corresponds to signal anisotropy, defined as anisotropic over isotropic component [63]. C) Color-coded map depicting main diffusion orientation from the same virtual section of the whole-brain dMRI dataset, at 75μm resolution. Color interpretation is similar to the SAXS map, where 2D orientation information was extracted as explained in Section 2.6.