- MCA Middle cerebral artery, ACA Anterior cerebral artery, PCA Posterior cerebral artery, P1 first segment of the posterior cerebral artery, P2 second segment of the posterior cerebral artery, TICA Terminal internal carotid artery, CS Carotid siphons, VA Vertebral artery, BA Basilar artery, ICA Internal carotid artery, FVmean mean flow velocity, FVdia diastolic flow velocity, PI pulsatility index, L.I. Lindegaard Index, ONSD Optic nerve sheath diameter, ICP Intracranial pressure, CPP cerebral perfusion pressure