Luyten P R, Groen J P, Vermeulen J W, den Hollander J A
Philips Medical Systems, Best, The Netherlands.
Magn Reson Med. 1989 Jul;11(1):1-21. doi: 10.1002/mrm.1910110102.
Experimental procedures for obtaining localized 31P NMR spectra of humans by means of the ISIS sequence are discussed in detail. The technique is optimized for use with volume coils and with surface coils in order to measure localized 31P NMR spectra of different tissues and organs. Selective frequency-modulated (FM) inversion and excitation pulses are applied for optimal inversion or excitation despite B1 inhomogeneity. Pulse imperfection may lead to spurious signal contributions from outside the selected volume; this contamination is reduced by using long pulse intervals, by properly ordering the ISIS acquisitions, and by using FM excitation pulses. Simultaneous measurement of multiple volumes was implemented by including an additional selective inversion pulse, and an extension of the ISIS addition/subtraction scheme. Localized T1 measurements with surface coils are implemented by using a B1-insensitive inversion pulse in the inversion recovery sequence. The quantitative reproducibility of localized 31P NMR spectra was verified. Absolute metabolite concentration can be determined after a suitable calibration of the 31P NMR spectrum. Localized shimming is required to obtain localized 31P NMR spectra of excellent spectral resolution. This is done by monitoring the 1H NMR signal from water by a single-shot localization technique. The techniques discussed can be applied to obtain spectra of brain, liver, heart, and other organs. 31P NMR spectra of intracranial tumors demonstrate its applicability in the examination of patients.
详细讨论了通过ISIS序列获取人体局部31P NMR谱的实验步骤。该技术针对体线圈和表面线圈进行了优化，以便测量不同组织和器官的局部31P NMR谱。尽管存在B1不均匀性，但仍应用选择性调频（FM）反转和激发脉冲以实现最佳反转或激发。脉冲缺陷可能会导致所选体积之外的虚假信号贡献；通过使用长脉冲间隔、合理安排ISIS采集顺序以及使用FM激发脉冲来减少这种污染。通过加入额外的选择性反转脉冲和扩展ISIS加减法方案来实现多个体积的同时测量。在反转恢复序列中使用对B1不敏感的反转脉冲来实现用表面线圈进行局部T1测量。验证了局部31P NMR谱的定量重现性。在对31P NMR谱进行适当校准后，可以确定绝对代谢物浓度。需要进行局部匀场以获得具有出色光谱分辨率的局部31P NMR谱。这是通过单次定位技术监测来自水的1H NMR信号来完成的。所讨论的技术可用于获取脑、肝、心脏和其他器官的谱。颅内肿瘤的31P NMR谱证明了其在患者检查中的适用性。
