Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Circle of Willis: (A) Complete circle of Willis; (B) Full bilateral fetal PCAs. ACA: Anterior cerebral artery; ACoA: Anterior communicating artery; BA: Basilar artery; ICA: Internal carotid artery; MCA: Middle cerebral artery; PCA1: P1 segment of posterior cerebral artery; PCA2: P2 segment of posterior cerebral artery; PCoA: Posterior communicating artery
