Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland.
NMR Biomed. 2013 Sep;26(9):1113-24. doi: 10.1002/nbm.2925. Epub 2013 Feb 25.
Proton point-resolved spectroscopy (PRESS) localization has been combined with distortionless enhanced polarization transfer (DEPT) in multinuclear MRS to overcome the signal contamination problem in image-selected in vivo spectroscopy (ISIS)-combined DEPT, especially for lipid detection. However, homonuclear proton scalar couplings reduce the DEPT enhancement by modifying the spin coherence distribution under J modulation during proton PRESS localization. Herein, a J-refocused proton PRESS-localized DEPT sequence is presented to obtain simultaneously enhanced and localized signals from a large number of metabolites by in vivo (13) C MRS. The suppression of J modulation during PRESS and the substantial recovery of signal enhancement by J-refocused PRESS-localized DEPT were demonstrated theoretically by product operator formalism, numerically by the spin density matrix simulations for different scalar coupling conditions, and experimentally with a glutamate phantom at various TEs, as well as a colza oil phantom. The application of the sequence for localized detection of saturated and unsaturated fatty acids in the calf bone marrow and skeletal muscle of healthy subjects yielded high signal enhancements simultaneously obtained for all components.
质子点分辨波谱（PRESS）定位与无失真增强极化转移（DEPT）相结合，用于多核 MRS 中，以克服在图像选择体内波谱（ISIS）结合 DEPT 中信号污染的问题，特别是用于脂质检测。然而，同核质子标量耦合通过在质子 PRESS 定位期间的 J 调制下修改自旋相干分布，降低了 DEPT 增强。本文提出了一种 J 重聚焦质子 PRESS 定位 DEPT 序列，通过体内（13）C MRS 同时获得大量代谢物的增强和定位信号。通过乘积算符形式理论上证明了 PRESS 期间 J 调制的抑制以及 J 重聚焦质子 PRESS 定位 DEPT 实质上恢复信号增强的情况，通过针对不同标量耦合条件的自旋密度矩阵模拟进行数值验证，并通过不同 TE 下的谷氨酸幻影以及菜籽油幻影进行实验验证。该序列应用于健康受试者小腿骨髓和骨骼肌中饱和和不饱和脂肪酸的局部检测，可同时获得所有成分的高信号增强。
