Fig. 1

Gradient direction scheme to measure tangential and radial diffusion. Top, The concept of tangential and radial diffusion is outlined as well as the 2D ellipsoid with eigenvalues (λ) and eigenvectors (ε). Middle, The sketch outlines the anatomical region of interest (carotid artery) and the orientation of the 18 diffusion gradient directions on a hemicycle within a plane perpendicular to the longitudinal axis of the carotid artery (black arrows). Bottom, Representative in vivo DWI from a carotid artery at a b-value of 600 s/mm² for the 18 diffusion directions (white headless arrows)