Jun Hua1, Qin Qin1, Manus J. Donahue2, Jinyuan Zhou1, James J. Pekar1, Peter CM van Zijl1
1Dept. of Radiology, The Johns Hopkins University, Baltimore, MD, USA; 2Dept. of Clinical Neurology, University of Oxford, Oxford, UK
Vascular changes during functional brain activity occur predominantly in the arterioles, and an MRI method sensitive to such changes is expected to improve spatial and temporal specificity for fMRI. Vascular-space-occupancy (VASO) fMRI is a blood-nulling approach assessing total CBV changes. We introduce an approach called inflow VASO or iVASO, which nulls only blood flowing into the slice. By using a blood-nulling time comparable to arterial transit times (~700ms), iVASO signal was sensitized to predominantly arteriolar blood volume effects. This arteriolar character was subsequently reflected in an effectively immediate hemodynamic response for iVASO when studying visual activation.