Abstract #1169

High-resolution segmented-accelerated EPI using Variable Flip Angle FLEET with tailored slice profiles

Avery JL Berman ^1,2, Thomas Witzel^1,2, William A Grissom ^3,4, Daniel Park ¹, Kawin Setsompop^1,2,5, and Jonathan R. Polimeni^1,2,5

¹Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Boston, MA, United States, ²Department of Radiology, Harvard Medical School, Boston, MA, United States, ³Vanderbilt University Institute of Imaging Science, Nashville, TN, United States, ⁴Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, United States, ⁵Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA, United States

New evidence suggests that fMRI has spatial specificity at scales far below current voxel sizes, but encoding limits preclude single-shot EPI at sufficient spatial resolution. Segmented EPI can help overcome these limits, but is well-known to be temporally unstable. Here we propose a reordering of the EPI segments, known as FLEET, combined with variable progression of flip angles to maximize the image signal level and a tailored RF pulse design to maintain compatible slice profiles. We demonstrate that this approach provides stable segmented EPI acquisitions with negligible ghosting, and when combined with acceleration can provide submillimeter fMRI acquisitions at 3T.

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