RARE/Turbo Spin Echo Imaging with Simultaneous Multislice Wave-CAIPI

PurposeTo enable highly accelerated RARE/Turbo Spin Echo (TSE) imaging using Simultaneous MultiSlice (SMS) Wave-CAIPI acquisition with reduced g-factor penalty. MethodsSMS Wave-CAIPI incurs slice shifts across simultaneously excited slices while playing sinusoidal gradient waveforms during the readout of each encoding line. This results in an efficient k-space coverage that spreads aliasing in all three dimensions to fully harness the encoding power of coil sensitivities. The novel MultiPINS radiofrequency (RF) pulses dramatically reduce the power deposition of multiband (MB) refocusing pulse, thus allowing high MB factors within the Specific Absorption Rate (SAR) limit. ResultsWave-CAIPI acquisition with MultiPINS permits whole brain coverage with 1 mm isotropic resolution in 70 s at effective MB factor 13, with maximum and average g-factor penalties of g(max)=1.34 and g(avg)=1.12, and without R penalty. With blipped-CAIPI, the g-factor performance was degraded to g(max)=3.24 and g(avg)=1.42; a 2.4-fold increase in g(max) relative to Wave-CAIPI. At this MB factor, the SAR of the MultiBand and PINS pulses are 4.2 and 1.9 times that of the MultiPINS pulse, while the peak RF power are 19.4 and 3.9 times higher. ConclusionCombination of the two technologies, Wave-CAIPI and MultiPINS pulse, enables highly accelerated RARE/TSE imaging with low SNR penalty at reduced SAR. Magn Reson Med, 2015. (c) 2015 Wiley Periodicals, Inc. Magn Reson Med 73:929-938, 2015. (c) 2014 Wiley Periodicals, Inc.