INSERM, UMR 1099, Rennes F-35000, France.
J Magn Reson. 2013 Mar;228:76-80. doi: 10.1016/j.jmr.2012.12.014. Epub 2013 Jan 7.
The double spin echo is the basis of the point resolved spectroscopy (PRESS) sequence. In this study we sought to investigate the effects of a broadband 180° pulse - incorporated in the PRESS sequence at the location of the first echo (gPRESS) - on the citrate resonances, chosen as a model of strongly coupled spin system. A significant signal modulation generated by the additional 180° pulse was predicted with simulations and observed experimentally in the citrate resonances. No effects were observed on the singlet resonance of glycine and the weakly coupled resonances of lactate. The phenomenon observed in gPRESS was attributed to the off-diagonal Hamiltonian elements responsible for a coherence transfer occurring throughout the evolution periods. The results of this study show that it is necessary to assess the effects of broadband 180° pulses on strongly coupled spin systems, since these pulses can selectively modify the spectral shape of strongly coupled resonances.
双回波自旋回波是点分辨波谱（PRESS）序列的基础。在这项研究中，我们试图研究在第一个回波（gPRESS）位置处包含在 PRESS 序列中的宽带 180°脉冲对柠檬酸共振的影响，选择柠檬酸共振作为强耦合自旋系统的模型。模拟预测并在柠檬酸共振中实验观察到附加 180°脉冲产生的显著信号调制。在甘氨酸的单峰共振和乳酸的弱耦合共振上没有观察到任何影响。在 gPRESS 中观察到的现象归因于负责在整个演化期间发生相干转移的非对角哈密顿元。这项研究的结果表明，有必要评估宽带 180°脉冲对强耦合自旋系统的影响，因为这些脉冲可以选择性地改变强耦合共振的光谱形状。
