Fig. 3.

Selective digital subtraction angiogram of a microcatheter injection of the basilar artery (BA). The entire Circle of Willis (CoW) is visualized in this anteroposterior view. (A) A flow directed microcatheter injection in the distal the BA shows filling of the superior cerebellar arteries (SCA), posterior cerebral arteries (PCA), posterior communicating arteries (PCoA), middle cerebral arteries (MCA), and anterior cerebral arteries (ACA). Note that the BA maintains its natural curve. (B) A guide catheter injection in the right internal carotid artery (ICA) shows filling of the CoW and highlights the severe tortuosity of the carotid artery.