Fig. 1
From: Vascular tortuosity in relationship with hypertension and posterior fossa volume in hemifacial spasm
Three-dimensional illustration of vessel selection (blue square dot), centreline extraction (curvilinear yellow line) and length measurements (curvilinear blue line) of the a basilar artery, b dominant left vertebral and c hypoplastic right vertebral arteries, a view from behind. Yellow arrows indicate the horizontal level of the hypoglossal canals. The internal carotid arteries in the background in a are masked in b and c. The vessel length (Lv) is defined as the length of the centreline extraction of each arterial segment and the chord length (Lc) as the shortest distance between the origin and termination point of each arterial segment. The Lv and Lc were measured for each of the three arterial segments, and the tortuosity index derived as the ratio, Lv/Lc