High field balanced-SSFP fMRI: Examining a diffusion contrast mechanism using varied flip-angles
Gati J, Bowen C, Menon R, Mason J
Robarts Research Institute
Although T2* weighted, gradient echo based fMRI has become a standard acquisition tool for neuroscientific investigation, many questions still exist as to the spatial specificity of the functional patterns observed relative to neuronal activity. Two main problems persist with T2* weighted fMRI: (i) an oversensitivity to oxygenation changes in large draining veins located distal to the site of activation; and (ii) an inability to perform robust T2* fMRI analysis in regions of strong field inhomogeneity. This paper proposes the use of b-SSFP at high field (4T) using on-resonance acquisitions. We show b-SSFP fMRI acquisitions have comparable sensitivity to the BOLD mechanism as traditional T2*-EPI acquisitions. Additionally, we demonstrate increased sensitivity with flip angle in tissue, consistent with a diffusion contrast mechanism, and negative signal changes within obvious draining veins, aiding large vessel suppression.