Study Abstract: Sub-millimeter functional imaging at ultrahigh field (UHF) strengths has the potential to capture cortical layer-specific functional information flow within and across brain systems. Recent sequence advancements of fMRI signal readout and contrast generations resulted in wide adaptation of layer-fMRI protocols across the global UHF neuroimaging community. However, most layer-fMRI applications are confined to one of ≈100 privileged UHF imaging centers, and sequence contrasts with unwanted sensitivity to large draining veins. In this work, we propose the application of vein-free vascular space occupancy (VASO) sequences at widely accessible 3T scanners. We aim to implement, characterize and apply a CBV-sensitive VASO sequence setup for 3T. We find that the longer T2*, and shorter T1 relaxation times at 3T can account for some of the lower z-magnetization in the inversion-recovery VASO sequence compared to 7T and 9.4T. Since 3T fMRI does not provide as much SNR compared to 7T, thermal-noise dominated layer-fMRI experiments at 3T require longer scan duration. In order to mitigate unrealistically long experiments, we aimed to increase the readout efficiency compared to previous 7T layer-fMRI VASO. This is done by means of utilizing fat saturation with binomial pulses, and segmented in-plane segmented trajectory, and externalizing phase navigators from the shot-specific readout. We test the utility of this setup for visual tasks, for motor tasks, and for movie watching tasks. We conclude that layer-fMRI VASO is applicable at 3T without too much further ado.

Link to Zip file with all participants (96GB): https://layerfmri.page.link/3TVASO_groupdata