The carotid cistern.
D002343:Carotid Artery, Internal / Q000000981:diagnostic imaging*; D002533:Cerebral Angiography; D006801:Humans; D009880:Ophthalmic Artery / Q000000981:diagnostic imaging*; D009900:Optic Nerve / Q000000981:diagnostic imaging*; D011011:Pneumoencephalography; D013346:Subarachnoid Space / Q000000981:diagnostic imaging*; D014056:Tomography, X-Ray