3D single‐shot VASO using a maxwell gradient compensated GRASE sequence

The vascular space occupancy (VASO) method was recently proposed as a functional MRI (fMRI) method that is capable of detecting activation‐related changes in blood volume (CBV), without the need for a blood‐pool contrast agent. In the present work we introduce a new whole‐brain VASO technique that is based on a parallel‐accelerated single‐shot 3D GRASE (gradient and spin echo) readout. The GRASE VASO sequence employs a flow‐compensated correction scheme for concomitant Maxwell gradients which is necessary to avoid smearing artifacts that may occur due to violation of the Carr–Purcell–Meiboom–Gill (CPMG) condition for off‐resonance excitation. Experiments with 6 min of visual‐motor stimulation were performed on eight subjects. At P < 0.01, average percent signal change and t ‐score for visual stimulation were −3.11% and −8.42, respectively; activation in left and right motor cortices and supplementary motor area was detected with −2.75% and −6.70, respectively. Sensitivity and signal changes are comparable to those of echo‐planar imaging (EPI)‐based single‐slice VASO, as indicated by additional visual‐task experiments (−3.39% and −6.93). The method makes it possible to perform whole‐brain cognitive activation studies based on CBV contrast. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.