Accelerated SMS-FSE with Long Hard Pulse Trains and Spatially Invariant FID Suppression

Simultaneous multi-slice (SMS) FSE in [1] was shown to be efficient for slice acceleration without much loss of signals. Despite its gains, conventional SMS-FSE, which employs high-flip-angle, spatially selective multi-band RF pulses in both excitation and refocusing, remains challenging particularly on high magnetic field due to high energy deposition and limited echo train length (ETL), eventually leading to low imaging efficiency. To alleviate this problem, we recently introduced a variable-flip-angle (VFA) SMS-FSE imaging with long hard pulse trains in which spatially selective multi-band RF pulses are used only for excitation while all refocusing RF pulses are short and non-selective2. Nevertheless, this approach still remains sub-optimal due to the 180° phase cycling in the refocusing pulse trains over two averages for FID suppression. Thus, the purpose of this work is to develop a novel, accelerated SMS-FSE with long hard pulse trains and spatially invariant FID suppression in which sharable FID artifacts are directly constructed using only 2-TR calibration scan instead of 2-average phase cycling scan and then subtracted. It is demonstrated that the proposed SMS-FSE with an SMS factor of 7 makes it possible to complete whole brain imaging only in 15 sec without apparent artifacts and noise.