Manus J. Donahue1, Hans Hoogduin2, Peter CM van Zijl3,4, Peter Jezzard1, Reinoud Pieter Harmen Bokkers2, Matthias JP van Osch5, Jaco J.M. Zwanenburg2, Peter Luyten2, Jeroen Hendrikse2
1Clinical Neurology, The University of Oxford, Oxford, UK; 2University Medical Center Utrecht, Utrecht, Netherlands; 3Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, USA; 4FM Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, USA; 5Leiden University Medical Center, Leiden, Netherlands
B0-dependence of gradient-echo BOLD-fMRI contrast was investigated in the same subjects at 1.5T, 3.0T and 7.0T by performing (1) BOLD-fMRI (visual) in the presence of flow-dephasing gradients (b=100 s/mm2) at multiple TEs, (2) BOLD-fMRI (visual) at high (1.5x1.5x1.5mm3) and low (3.5x3.5x3.5mm3) spatial resolution, and (3) BOLD-fMRI (breath hold). Extravascular (EV) contributions to total BOLD ΔR2* were 4513%, 7011% and 9219% at 1.5T, 3.0T and 7.0T, respectively, suggesting that BOLD fMRI performed at 7.0T is almost purely EV. Caution should be exercised when comparing total BOLD reactivity at different B0 due to different EV contributions.