Fig. 5. Time-dependent axial diffusivity D(t) and fit parameters (D_∞, c) estimated in brain lesions (red) and normal-appearing white matter (NAWM, blue) of five MS patients using monopolar PGSE.

a D(t)-values are plotted as points for each subject, along with corresponding mean values and error bars representing the SE over five subjects, and the corresponding fit to Eq. (1) confirms the $1/\sqrt{t}$ functional form of D(t). b The bulk diffusivity D_∞ along axons is significantly larger in MS lesions than that in NAWM. c The corresponding strength c of restrictions along axons is smaller in MS lesions than in NAWM. In b and c, each patient is represented by a blue segment. The parameter differences between MS lesions and NAWM are compared by using one-sided Wilcoxon signed-rank test (*P-value < 0.05).