Fig. 4

Fractional anisotropy (FA) map reconstructions in healthy and diabetic patients. Representative images of a healthy subject (a) and a diabetic patient (b) showing T2-weighted images of the distal sciatic nerve and corresponding color-coded fractional anisotropy (FA) maps calculated with the 20-directional standard model (DTI₂₀) and the reduced models 1, 2, and 3. Segmentation of the nerve portion is indicated by a white contour. Insets show a magnification of the nerve. Model 1 achieves the best approximation to DTI₂₀ in both healthy and diseased nerve tissue, while models 2 and 3 yield good but inferior accuracy