Fourier analysis of cerebrospinal fluid flow velocities: MR imaging study

An interleaved pseudocinematographic FLASH (fast low-angle shot) sequence with additional pulsed gradients for flow encoding was used to quantify cerebrospinal fluid (CSF) flow velocities and CSF production. Flow-dependent phase information was obtained by subtracting two differently encoded phase images. The phase information in the resultant image was converted to flow velocity with a calibration curve with the slope 26.5 radian · m^-1 · sec. The velocity versus time function was Fourier transformed and a continuous curve was fitted to the measured data with use of the first three harmonics. The in vivo measurements showed a significant variation in flow velocities in the cerebral aqueduct (range, 6-51 mm/sec). Calculated CSF production was in the range of 0.6-1.2 L/24 h. The present method gives valuable information about CSF hydrodynamics in an imaging time of less than 8 minutes.