Evaluating the Benefit of Parallel Transmission on tSNR in 3D-EPI-based fMRI at 7 Tesla

Motivation: Parallel transmission has been shown to improve the temporal SNR in fMRI studies at 7T when using 2D-EPI, while the benefits are less clear with 3D-EPI. Goal(s): To study the tSNR benefit of pTx in fMRI studies that use 3D-EPI at 7T. Approach: We compared both the modelled (t)SNR (based on the measured B1+) and the measured tSNR in a 3D-EPI functional scan at 7T between CP and pTx. Results: The (t)SNR of 3D-EPI is relatively B1+ robust. Consequently, pTx provided trivial benefits in most brain regions (<=4% in mean tSNR) except in B1+ starved areas such as the cerebellum. Impact: In the brain, at 7T, the (t)SNR of 3D-EPI is relatively B1+ robust, resulting in trivial tSNR benefit with pTx. The benefits only become impactful when multiple brain regions, including B1+ starved areas like the cerebellum, are of interest.