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Abstract #0301

Investigating the Field Strength Dependence of BOLD Onset Time

Ian D. Driver1, Susan T. Francis1, Penelope A. Gowland1

1Sir Peter Mansfield Magnetic Resonance Centre, University of Nottingham, Nottingham, United Kingdom

This work assesses the origin of a shift to earlier BOLD onset times with increasing field strength, observed in response to a visual stimulus. Potential causes due to inflowing blood and different relative contributions of arteries and veins as a result of T2* changes across field strength are ruled out. Rather, a delayed venous blood oxygenation response with respect to blood flow increases, accompanied by a reduced capillary extravascular signal contribution at 1.5 T, consistent with previous Monte Carlo simulations, can be shown to cause the later onset time at 1.5 T compared to 7T.