Comparison of the temporal response in perfusion and BOLD-based event-related functional MRI

Event-related functional MRI (ER-fMRI) based on both blood oxygen level-dep endent (BOLD) contrast and perfusion contrast has been recently developed t o study human brain activation due to brief stimulation. In this report, bo th BOLD- and perfusion-based ER-fMRI were directly compared using repeated single-trial, short visual stimulation (1 sec) in six human volunteers. The results show that the cerebral blood flow change reached a maximum approxi mately 1 sec earlier than the BOLD signal change (4.2 +/- 0.2 sec vs. 5.1 /- 0.2 sec after the stimulation, P < 0.05). The full width at half maximum of the hemodynamic response measured by perfusion was not significantly di fferent from that measured with BOLD (5.1 +/- 0.6 sec vs. 5.9 +/- 0.6 sec). A positive linear correlation was found between the maximum perfusion and maximum BOLD signal changes (r = 0.77, P = 0.07). Magn Reson Med 43:768-772 , 2000. (C) 2000 Wiley-Liss, Inc.