Department of Biomedical Engineering, Sungkyunkwan University, Suwon, Republic of Korea.
Department of Electrical and Electronic Engineering, Yonsei University, Seoul, Republic of Korea.
Magn Reson Med. 2017 Nov;78(5):1852-1861. doi: 10.1002/mrm.26595. Epub 2017 Jan 11.
To investigate the feasibility of chemical shift encoded, single-slab 3D GRASE for rapid fat-water separation within a single acquisition.
The proposed method incorporates signal-to-noise-ratio-optimal chemical shift encoding into single-slab 3D GRASE with variable flip angles. Chemical shift induced phase information was encoded in succession to different positions in k-space by inserting phase encoding blips between adjacent lobes of the oscillating readout gradients. To enhance imaging efficiency, signal prescription-based variable flip angles were used in the long refocusing pulse train. After echo-independent phase correction, missing signals in k-echo space were interpolated using convolution kernels that span over all echoes. Fat-water separation in a single acquisition was performed using both multi-echo fast spin echo and GRASE as compared to conventional multiacquisition fast spin echo with echo shifts.
The proposed single-slab 3D GRASE shows superior performance in accurately delineating cartilage structures compared to its counterpart, multi-echo 3D fast spin echo. Compared with multiacquisition fast spin echo with three echo shifts (63 min), the proposed method substantially speeds up imaging time (7 min), and achieves 0.6 mm isotropic resolution in knee imaging with reduced artifacts and noise.
We successfully demonstrated the feasibility of rapid chemical shift encoding and separation using the proposed, single-acquisition single-slab 3D GRASE for high resolution isotropic imaging within clinically acceptable time. Magn Reson Med 78:1852-1861, 2017. © 2017 International Society for Magnetic Resonance in Medicine.
研究在单次采集内通过化学位移编码单次激发 3D GRASE 实现快速油水分离的可行性。
该方法将信噪比最优的化学位移编码与可变翻转角的单次激发 3D GRASE 相结合。通过在相邻的读出梯度的波瓣之间插入相位编码脉冲，将化学位移引起的相位信息依次编码到 k 空间中的不同位置。为了提高成像效率，在长重聚焦脉冲序列中使用基于信号规定的可变翻转角。在进行独立于回波的相位校正后，使用跨越所有回波的卷积核对 k 回波空间中的缺失信号进行内插。与传统的多采集快速自旋回波（具有回波移位）相比，在单次采集内同时使用多回波快速自旋回波和 GRASE 进行油水分离。
与多回波 3D 快速自旋回波相比，所提出的单次激发 3D GRASE 在准确描绘软骨结构方面表现出优异的性能。与具有三个回波移位（63 分钟）的多采集快速自旋回波相比，该方法大大加快了成像时间（7 分钟），并在膝关节成像中实现了 0.6mm 的各向同性分辨率，同时减少了伪影和噪声。
我们成功地证明了在单次采集单次激发 3D GRASE 中使用所提出的方法进行快速化学位移编码和分离的可行性，该方法可在临床可接受的时间内实现高分辨率各向同性成像。磁共振医学 78：1852-1861，2017。© 2017 国际磁共振学会。
