LAUSR

ABSTRACT T2* weighted 3D Gradient Echo (GRE) acquisition is the main sequence used for Susceptibility Weighted Imaging (SWI) and Quantitative Susceptibility Mapping (QSM). These applications require a long echo time (TE) to build up phase contrast, requiring a long repetition time (TR), and leading to excessively lengthy scans. The long TE acquisition creates a significant amount of unused time within each TR, which can be utilized for either multi‐echo sampling or additional image encoding with the echo‐shift technique. The latter leads to significant saving in acquisition time while retaining the desired phase and T2* contrast. In this work, we introduce the Simultaneous Time Interleaved MultiSlice (STIMS) echo‐shift technique, which mitigates slab boundary artifacts by interleaving comb‐shaped slice groups with Simultaneous MultiSlice (SMS) excitation. This enjoys the same SNR benefit of 3D signal averaging as previously introduced multi‐slab version, where each slab group is sub‐resolved with kz phase encoding. Further, we combine SMS echo‐shift with Compressed Sensing (CS) Wave acceleration, which enhances Wave‐CAIPI acquisition/reconstruction with random undersampling and sparsity prior. STIMS and CS‐Wave combination thus yields up to 45‐fold acceleration over conventional full encoding, allowing a 15 sec full‐brain acquisition with 1.5 mm isotropic resolution at long TE of 39 ms at 3 T. In addition to utilizing empty sequence time due to long TE, STIMS is a general concept that could exploit gaps due to e.g. inversion modules in magnetization‐prepared rapid gradient‐echo (MPRAGE) and fluid attenuated inversion recovery (FLAIR) sequences. HIGHLIGHTSSTIMS exploits unused time in long TE scans for extra encoding using SMS echo‐shiftCompressed Sensing (CS) Wave harnesses sensitivity encoding and sparsityCombination of STIMS with CS‐Wave allows 45‐fold accelerated 3D‐GRESTIMS is a general concept that could improve efficiency in e.g. MP‐RAGE and FLAIR