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Fig 6. Sagittal drawing of the head showing the region covered by an initial section selective inversion pulse (shaded area) and that covered by the subsequent 90° pulse and acquisition without head movement (A) and with head movement downward in the superior-inferior direction between the initial inversion pulse and the 90° pulse (B). Possible directions of head motion–induced CSF flow at different times are also shown (curved arrows). With movement (B), the excitation and acquisition includes posterior areas of the subarachnoid space, which have experienced the inversion pulse as well as anterior areas that have not experienced it. These latter areas are likely to display high signal intensity, though the final result may be affected by CSF flow induced by the head motion. Initially, some CSF may move with the head while other portions of the CSF may move in the same direction later. When the head stops moving, there may be overshoot of the CSF moving with the head, followed by a later reversal of its direction of flow.
