He Xiaoxuan, Auerbach Edward J, Garwood Michael, Kobayashi Naoharu, Wu Xiaoping, Metzger Gregory J
Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, USA.
Magn Reson Med. 2021 Jul;86(1):17-32. doi: 10.1002/mrm.28682. Epub 2021 Jan 26.
To develop a 3D composite adiabatic spectral-spatial pulse for refocusing in spin-echo spectroscopy acquisitions and to compare its performance against standard acquisition methods.
A 3D composite adiabatic pulse was designed by modulating a train of parallel transmit-optimized 2D subpulses with an adiabatic envelope. The spatial and spectral profiles were simulated and validated by experiments to demonstrate the feasibility of the design in both single and double spin-echo spectroscopy acquisitions. Phantom and in vivo studies were performed to evaluate the pulse performance and compared with semi-LASER with respect to localization performance, sequence timing, signal suppression, and specific absorption rate.
Simultaneous 2D spatial localization with water and lipid suppression was achieved with the designed refocusing pulse, allowing high-quality spectra to be acquired with shorter minimum TE/TR, reduced SAR, as well as adaptation to spatially varying B and field inhomogeneities in both prostate and brain studies.
The proposed composite pulse can serve as a more SAR efficient alternative to conventional localization methods such as semi-LASER at ultrahigh field for spin echo-based spectroscopy studies. Subpulse parallel-transmit optimization provides the flexibility to manage the tradeoff among multiple design criteria to accommodate different field strengths and applications.
开发一种用于自旋回波光谱采集重聚焦的三维复合绝热频谱空间脉冲，并将其性能与标准采集方法进行比较。
通过用绝热包络调制一系列平行发射优化的二维子脉冲来设计三维复合绝热脉冲。通过实验模拟和验证空间和频谱分布，以证明该设计在单自旋回波光谱采集和双自旋回波光谱采集中的可行性。进行了体模和体内研究以评估脉冲性能，并在定位性能、序列定时、信号抑制和比吸收率方面与半激光进行比较。
使用设计的重聚焦脉冲实现了水和脂质抑制的同时二维空间定位，从而能够以更短的最小回波时间/重复时间采集高质量光谱，降低比吸收率，并适应前列腺和脑部研究中空间变化的B场和磁场不均匀性。
对于基于自旋回波的光谱研究，所提出的复合脉冲可作为传统定位方法（如半激光）在超高场下更具比吸收率效率的替代方法。子脉冲并行发射优化提供了灵活性，可在多个设计标准之间进行权衡，以适应不同的场强和应用。
