Bulk motion-independent analyses of water diffusion changes in the brain during the cardiac cycle.

We evaluated dynamic changes in water diffusion in the brain during the cardiac cycle by using cine diffusion MRI. On a 1.5-T MRI, ECG-triggered single-shot diffusion echo planar imaging was used with sensitivity encoding, halfscan, and rectangular field of view techniques for minimizing bulk motion effects such as brain pulsation, with a data-sampling window of 3 ms. The apparent diffusion coefficient (ADC) and fractional anisotropy (FA) in the white matter zone were determined in ten healthy volunteers and then compared with the intracranial volume change (ICVC) revealed by phase-contrast cine MRI during the cardiac cycle. In addition, a frequency analysis of these waveforms was performed. ADC and FA values changed significantly during the cardiac cycle, despite minimizing the effect of bulk motion, i.e., independent of bulk motion. The ADC was synchronized with the ICVC during the cardiac cycle. A significant positive correlation was noted among their amplitudes. Analysis of the dynamic change of water diffusion by use of cine diffusion MRI facilitates the assessment of intracranial conditions.