Abstract #0220

An Intra-Subject Investigation of the BOLD Contrast Mechanism in Response to Visual Stimulation and Breath Hold at 1.5T, 3.0T and 7.0T: Insight Into the Extravascular Sensitivity, Resolution-Dependence and Vascular Origins of BOLD Contrast

Manus J. Donahue¹, Hans Hoogduin², Peter CM van Zijl^3,4, 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.