Fig. 2

Mean CSF velocity measurements over one cardiac cycle. Representative CSF velocity changes in one subject over one cardiac cycle as measured at mid-C2 in a volunteer during upright and supine body orientations. Notice the wider systolic peak during systole (positive values) in supine compared to the narrower one observed in upright posture. Furthermore, the magnitudes of CSF velocities appear to be consistently lower in upright compared to supine (bottom images), indicated by the CSF signal intensities on the phase image (red circle of spinal canal excluding cord). Note that the dark intensity is cranio-caudal whilst bright intensity is caudo-cranial direction