Figure 1.

Flowchart of summarizing this study. CCA = common carotid artery, ECA = external carotid artery, ICA = internal carotid artery, PSV = peak systolic velocity. ∗Ultrasound examination was performed by an experienced sonographer who earned the certification of Registered Vascular Technologist. ^†The PSV ratio was calculated with the PSV of ICA divided by the PSV of CCA obtained at the CCA, 2 cm proximal to the carotid bifurcation. ^‡Ultrasound results were interpreted by a vascular surgeon who earned the certification of Registered Physician for Vascular Interpretation.