Unaliasing of Multiband Multislice EPI and GRE Imaging with GRAPPA

Steen Moeller¹, Essa Yacoub¹, Eddie Auerbach¹, Cheryl Ohlman¹, Kamil Ugurbil¹

Whole brain fMRI at ultra high field with large reduction factors requires accurate treatment of the sparsely sampled data. While maintaining conventional techniques for unalasing, the effects of only using 5x4 GRAPPA kernel size are demonstrated for 4x4 aliasing. Larger kernels must be used to capture the more complex sensitivity profiles. The correct use of navigator echoes for ACS data is also investigated. Significant image improvements are demonstrated in rapid whole brain coverage using 16 fold acceleration, with 4 fold originating from simultaneous acquisition of multiple slices, enhancing our ability to perform rapid, whole brain fMRI at ultrahigh fields like 7T.