The respiratory modulation of intracranial cerebrospinal fluid pulsation observed on dynamic echo planar images.

Pressure changes in cerebrospinal fluid (CSF) that occur with respiration rhythms have been studied in animals and humans for more than 100 years. This phenomenon has been recently validated in vivo on MR images by applying spectral analysis to signal-time curves at selected regions of interest. However, selecting regions of interest requires knowledge of physiology and anatomy, and manual selection is time consuming. We postulate that CSF pulsation is passively modulated by intra-thoracic pressure that is secondary to respiration, and this pulsation can be observed as a flow-related enhancement on MR images. To investigate the spatiotemporal patterns of respiratory rhythms in human brains, we conducted a study on MR scanning of 12 healthy volunteers who performed normal-breathing and breath-holding experiments during scanning. Spectral analysis, spectroscopic images, independent component analysis and signal measurements in selected regions were applied to dynamic MR images acquired from these volunteers. Through independent component analysis, respiratory rhythms were found at the vicinity of ventricles and CSF areas in nine subjects in normal-breathing experiments. In breath-holding experiments, respiratory rhythm suppression and vessel dilation were observed in 8 and 10 subjects, respectively. Information obtained from this study further elucidates the respiratory modulation of CSF in vivo.