Center for Clinical Spectroscopy, Department of Radiology, Brigham & Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
J Magn Reson Imaging. 2011 Jun;33(6):1447-55. doi: 10.1002/jmri.22555.
To describe an enhanced version of a localized correlation spectroscopy (L-COSY) by introducing adiabatic radiofrequency (RF) pulses for localization in two dimensions. Adiabatic pulses will improve slice selection profile and reduce chemical shift artifacts. Optimized Mao and adiabatic hyperbolic secant pulses are tested in vivo.
Region of interest is localized by a 90° nonselective adiabatic RF pulse followed by two pairs of adiabatic RF pulses and a terminal 90° RF sinc pulse. Slice profiles for both refocusing pulses and chemical shift artifacts are measured in a water-oil phantom for L-COSY and AL-COSY. In vivo results of both COSY sequences are shown from muscle and brain on a 3 Tesla (T) scanner.
Chemical shift artifacts were reduced with AL-COSY compared with L-COSY. Slice profiles of adiabatic pulses were found to be sharper and more symmetrical than those of traditional Mao pulses. One-dimensional (1D) phantom studies showed longer T2 values using AL-COSY sequence. Comparison of 2D spectra obtained revealed spectroscopic peak volume improvements in AL-COSY and less residual water. In vivo 1D comparison showed more inphase and sharper peaks in AL-COSY spectrum.
The AL-COSY sequence is an improved sequence due to sharper slice selection profiles, reduction of chemical shift artifacts, peak volume improvements in 2D techniques, and less J-modulation.
通过在二维空间中引入绝热射频（RF）脉冲来描述局部相关光谱学（L-COSY）的增强版本。绝热脉冲将改善切片选择轮廓并减少化学位移伪影。在体内测试了优化的 Mao 和绝热双曲正割脉冲。
通过 90°非选择性绝热 RF 脉冲对感兴趣区域进行局部化，然后施加两对绝热 RF 脉冲和一个终端 90°RF sinc 脉冲。在水-油体模中测量 L-COSY 和 AL-COSY 的重聚焦脉冲和化学位移伪影的切片轮廓。在 3T 扫描仪上显示来自肌肉和大脑的两种 COSY 序列的体内结果。
与 L-COSY 相比，AL-COSY 减少了化学位移伪影。发现绝热脉冲的切片轮廓比传统 Mao 脉冲更锐利且更对称。一维（1D）幻影研究表明，使用 AL-COSY 序列的 T2 值更长。对获得的二维光谱进行比较表明，AL-COSY 中的光谱峰体积有所改善，残留水更少。体内 1D 比较表明，AL-COSY 谱中的同相信号更锐利。
AL-COSY 序列是一种改进的序列，因为它具有更锐利的切片选择轮廓，减少了化学位移伪影，在二维技术中提高了峰体积，并减少了 J 调制。
