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

Figure 2

Posterior CoW variants a₁. Unilateral FTP (P1 ≥ 1 mm) and contralateral PcomA patent a₂. Bilateral FTP (bilateral P1 ≥ 1 mm) b₁. Absence or hypoplasia of unilateral PcomA b₂. Hypoplasia or absence of both PcomA c₁. Unilateral FTP and hypoplasia or absence of the ipsilateral P1 c₂. Unilateral FTP (ipsilateral P1 ≥ 1 mm) and hypoplasia or absence of the contralateral PcomA c₃. Unilateral FTP (hypoplasia or absence of the ipsilateral P1) and hypoplasia or absence of the contralateral PcomA c₄. Bilateral FTP with hypoplasia or absence of both P1 segments c₅. Bilateral FTP with hypoplasia or absence of one P1 segment d. Unilateral FTP and ipsilateral complete posterior cerebral artery; they do not have direct contact.