Fig. 1

Measurement of a angle α, the angle between the internal carotid artery (ICA) and common carotid artery (CCA), and b intima-media thickness (IMT). In (a), dotted lines indicate the vessels’ center lines. Angle α is designated to be the angle formed by the intersection of these two lines. Representative cases of a relatively small angle (left) and large angle (right) are shown. IMT at the proximal ICA near wall is marked ICA-IMT. In (b), the location where CCA-IMT and CCA diameter are measured is shown with a white square. The dotted line with double arrowheads indicates the location 2.0 cm proximal from the vessel bifurcation. The solid line with double arrowheads and double dotted lines in the enlarged view (right) indicate the CCA diameter and CCA-IMT, respectively