CTA Characteristics of the Circle of Willis and Intracranial Aneurysm in a Chinese Crowd with Family History of Stroke

Figure 1

Anterior CoW variants a₁. Hypoplastic left-side A1 segment a₂. Hypoplastic right-side A1 segment a₃. Absence of left-side A1 segment a₄. Absence of right-side A1 segment b. Absence or hypoplasia of the AcomA c. Hypoplasia of unilateral anterior cerebral artery d₁. Trifurcation of the anterior cerebral artery d₂. The azygos anterior cerebral artery.