Data acquisition by phase-contrast magnetic resonance imaging. Sagittal scout view sequences were used as localizers to select the anatomical levels for flow quantification. The selected acquisition planes were perpendicular to the presumed flow direction. Sections through the aqueduct of Sylvius (a) and the C2-C3 subarachnoid space (b) were used for CSF flow measurement. By varying the velocity encoding, the same cervical section level (c) was used to measure vascular flows in the left and right internal carotid arteries (ICAs), vertebral arteries (VAs), internal jugular veins (IJVs) and epidural veins (EVs). Figures 1(a), (b) and (c) represent the flow acquisition over the cardiac cycle. See also additional file: Movie1 for the original data used to perform this analysis'.