Department of Radiology, Seoul National University Hospital, Seoul, Republic of Korea.
J Magn Reson. 2012 Oct;223:90-7. doi: 10.1016/j.jmr.2012.07.017. Epub 2012 Aug 2.
The performance of multiple quantum filters (MQFs) can be disappointing when the background signal also arises from coupled spins. Moreover, at 3.0 T and even higher fields the majority of the spin systems of key brain metabolites fall into the strong-coupling regime. In this manuscript we address comprehensively, the importance of the phase of the multiple quantum coherence-generating pulse (MQ-pulse) in the design of MQFs, using both product operator and numerical analysis, in both zero and double quantum filter designs. The theoretical analyses were experimentally validated with the examples of myo-inositol editing and the separation of glutamate from glutamine. The results demonstrate that the phase of the MQ-pulse per se provides an additional spectral discrimination mechanism based on the degree of coupling beyond the conventional level-of-coherence approach of MQFs. To obtain the best spectral discrimination of strongly-coupled spin systems, therefore, the phase of the MQ-pulse must be included in the portfolio of the sequence parameters to be optimized.
当背景信号也来自耦合自旋时，多量子滤波器（MQF）的性能可能会令人失望。此外，在 3.0T 甚至更高的场强下，大多数关键脑代谢物的自旋系统都处于强耦合状态。在本文中，我们全面地解决了在多量子滤波器设计中，多量子相干产生脉冲（MQ 脉冲）的相位的重要性问题，同时使用了乘积算符和数值分析，无论是在零量子滤波器还是双量子滤波器的设计中。我们使用肌醇编辑和谷氨酸与谷氨酰胺分离的例子对理论分析进行了实验验证。结果表明，MQ 脉冲的相位本身提供了一种额外的基于耦合程度的光谱分辨机制，超越了 MQF 的传统相干度方法。因此，为了获得对强耦合自旋系统的最佳光谱分辨，MQ 脉冲的相位必须包含在要优化的序列参数组合中。
