Gagoski Borjan A, Bilgic Berkin, Eichner Cornelius, Bhat Himanshu, Grant P Ellen, Wald Lawrence L, Setsompop Kawin
Fetal-Neonatal Neuroimaging & Developmental Science Center, Boston Children's Hospital, Boston, MA, USA.
Department of Radiology, Harvard Medical School, Boston, MA, USA.
Magn Reson Med. 2015 Mar;73(3):929-938. doi: 10.1002/mrm.25615. Epub 2015 Feb 2.
To enable highly accelerated RARE/Turbo Spin Echo (TSE) imaging using Simultaneous MultiSlice (SMS) Wave-CAIPI acquisition with reduced g-factor penalty.
SMS 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.
Wave-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 gmax = 1.34 and gavg = 1.12, and without √R penalty. With blipped-CAIPI, the g-factor performance was degraded to gmax = 3.24 and gavg = 1.42; a 2.4-fold increase in gmax 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.
Combination of the two technologies, Wave-CAIPI and MultiPINS pulse, enables highly accelerated RARE/TSE imaging with low SNR penalty at reduced SAR.
通过同时多层（SMS）Wave-CAIPI采集实现高加速快速自旋回波（RARE/Turbo Spin Echo，TSE）成像，并降低g因子惩罚。
SMS Wave-CAIPI在每条编码线读出期间播放正弦梯度波形时，会在同时激发的层面间产生层面偏移。这导致了一种高效的k空间覆盖，将混叠分布在所有三个维度上，以充分利用线圈灵敏度的编码能力。新型的多针射频（RF）脉冲显著降低了多频段（MB）重聚焦脉冲的功率沉积，从而在比吸收率（SAR）限制内允许高MB因子。
使用多针的Wave-CAIPI采集能够在有效MB因子为13时，于70秒内实现全脑覆盖，各向同性分辨率为1毫米，最大和平均g因子惩罚分别为gmax = 1.34和gavg = 1.12，且无√R惩罚。使用 blipped-CAIPI时，g因子性能降至gmax = 3.24和gavg = 1.42；相对于Wave-CAIPI，gmax增加了2.4倍。在此MB因子下，多频段和针状脉冲的SAR分别是多针脉冲的4.2倍和1.9倍，而峰值RF功率则分别高出19.4倍和3.9倍。
Wave-CAIPI和多针脉冲这两种技术的结合，能够在降低SAR的情况下，实现具有低信噪比惩罚的高加速RARE/TSE成像。
