Comparison of 3D BOLD functional MRI with spiral acquisition at 1.5 and 4.0 T

In order to investigate the merit of high held strength for BOLD-contrast-b ased functional magnetic resonance imaging (fMRI) studies, multishot gradie nt echo fMRI experiments during motor cortex activation were performed on 1 .5- and 4.0-T scanners with equivalent hardware, on the same volunteers. in these studies, artifactual vascular enhancement related to inflow effects was minimized, and large brain areas were covered by using a 3D scan techni que. Temporal signal stability was optimized by using spiral readout gradie nts. The sensitivity for detection of activated regions was assessed by mea suring the number of "activated voxels" and their average t score in predef ined regions of interest. When comparing fMRI experiments with the same tot al scan time, performed on six subjects, and with acquisition parameters op timized for each field strength separately the 4.0-T scanner proved to give superior results, with a 70% greater number of activated voxels and a 20% higher average t score for the activated voxels.