File:Cerebral angiography, arteria vertebralis sinister injection.JPG

Cerebral angiography, injection in the left vertebral artery, with retrograde flow in the contralateral vertebral artery, the basilar artery and the posterior communicating artery. The posterior cerebral circulation can be seen, including the posterior part of the arterial circle of Willis.

From Wikipedia Commons, angiography taken by angiographer and released to public domain

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