A comparison of fast MR scan techniques for cerebral activation studies at 1.5 Tesla

To evaluate the sensitivity of fast, gradient-echo MR scan techniques in their ability to detect blood oxygenation level dependent (BOLD) signal changes in task activation studies, three dedicated fast scan techniques, each with whole-brain coverage, were compared during a 3-min finger tapping paradigm on nine normal volunteers on a clinical 1.5 T scanner. Multislice (2D) single-shot spiral, 3D spiral, and multislice (2D) single-shot EPI scan techniques were done with similar temporal and spatial resolutions on each of the volunteers in random order. After image registration and statistical analysis, the sensitivity to detect activation was evaluated for the techniques by calculating t scores and number of activated voxels in predetermined regions of interest, including the contralateral primary sensorimotor cortex, the premotor region, the parietal region, the supplementary motor area, and the ipsilateral cerebellum. Baseline images acquired with the three techniques were qualitatively comparable and had a similar effective spatial resolution of around 5 x 5 x 5 mm³, as determined from autocorrelation analysis. The anatomical coverage was somewhat reduced (4 less slices per volume) with EPI at the identical temporal resolution of 1.76 s for all techniques. The use of multislice 2D spiral scan for motor cortex fMRI experiments provided for a superior overall temporal stability, and an increased sensitivity compared with multislice 2D EPI, and 3D spiral scan. The difference in sensitivity between multislice 2D spiral end EPI scans was small, in particular in the case of a ramp-sampled version of EPI. The difference in performance is attributed mainly to the difference in scan- to-scan stability.