Kimberly D. Brewer1,2, Ryan CN D'Arcy2,3, Chris V. Bowen2,4, Steven D. Beyea2,4
1Department of Physics, Dalhousie University, Halifax, Nova Scotia, Canada; 2Institute for Biodiagnostics (Atlantic), National Research Council of Canada, Halifax, Nova Scotia, Canada; 3Departments of Psychology and Radiology, Dalhousie University, Halifax, Nova Scotia, Canada; 4Departments of Physics, Radiology and Biomedical Engineering, Dalhousie University, Halifax, Nova Scotia, Canada
The presence of magnetic susceptibility induced field gradients (SFGs) in regions such as the orbital frontal cortex results in significant signal loss and image distortion in functional MRI studies. To overcome this problem we propose a new technique that combines an approach in which multiple spiral images are acquired asymmetric to a spin-echo, with each spiral obtained using a different z-shim value (optimized on a slice-by-slice basis). This method, called Z-shim ASE spiral, permits significant signal recovery in regions of SFGs, resulting in increased SNR and fMRI signal recovery.