Use of k-space segmentation in MR velocity mapping for rapid quantification of CSF flow

In this work, a k-space segmentation technique for quantitative studies of pulsatile cerebrospinal fluid (CSF) flow is suggested. Three k-space lines are sampled for each of two interleaved gradient-echo sequences (velocity-compensated and velocity-encoded) within each repetition interval. Nine cardiac phases are obtained at a heart rate of 60 bpm with maintained nominal resolution and a factor of 3 in reduction of acquisition time relative to our conventional nonsegmented flow quantification protocol. Segmented and conventional sequences were compared in phantoms, in healthy volunteers, and in two patients with clinically suspected normal pressure hydrocephalus. Good agreement between flow curves obtained with the two sequences was demonstrated in vitro as well as in vivo. A slight underestimation of flow values in volunteers was attributed to data filtering when using the segmented sequence. Because the CSF circulation is complex and tightly connected to the vascular circulation, specific clinical applications may require flow studies at multiple positions and with different velocity encoding. In such cases, the proposed sequence can be used to gain time, but alternatively, the segmentation technique can be used to further increase spatial resolution within reasonable examination times.