Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
Magn Reson Med. 2011 Sep;66(3):609-18. doi: 10.1002/mrm.22857. Epub 2011 Mar 9.
Glycine is a key metabolic intermediate required for the synthesis of proteins, nucleic acids, and other molecules, and its detection in cancer could, therefore, provide biologically relevant information about the growth of the tumor. Here, we report measurement of glycine in human brain and gliomas by an optimized point-resolved spectroscopy sequence at 3 T. Echo time dependence of the major obstacle, myo-inositol (mI) multiplet, was investigated with numerical simulations, incorporating the 3D volume localization. The simulations indicated that a subecho pair (TE(1) , TE(2) ) = (60, 100) ms permits detection of both glycine and mI with optimum selectivity. In vivo validation of the optimized point-resolved spectroscopy was conducted on the right parietal cortex of five healthy volunteers. Metabolite signals estimated from LC Model were normalized with respect to the brain water signal, and the concentrations were evaluated assuming the total creatine concentration at 8 mM. The glycine concentration was estimated as 0.6 ± 0.1 mM (mean ± SD, n = 5), with a mean Cramér-Rao lower bound of 9 ± 1%. The point-resolved spectroscopy sequence was applied to measure the glycine levels in patients with glioblastoma multiforme. Metabolite concentrations were obtained using the water signal from the tumor mass. The study revealed that a subset of human gliomas contains glycine levels elevated 1.5-8 fold relative to normal.
甘氨酸是合成蛋白质、核酸和其他分子所需的关键代谢中间产物，因此，在癌症中检测到甘氨酸可以提供关于肿瘤生长的生物学相关信息。在这里，我们报告了在 3T 下通过优化的点分辨波谱序列测量人脑中甘氨酸和神经胶质瘤的情况。通过数值模拟研究了主要障碍肌醇（mI）多重峰的回波时间依赖性，模拟结果表明，亚回波对（TE(1)，TE(2)）=（60，100）ms 可以最佳选择性地检测甘氨酸和 mI。在五名健康志愿者的右顶叶皮层上对优化的点分辨波谱进行了体内验证。使用 LC Model 从 LC Model 估计的代谢物信号相对于脑水信号进行了归一化，并假设总肌酸浓度为 8 mM 来评估浓度。甘氨酸浓度估计为 0.6 ± 0.1 mM（平均值 ± SD，n = 5），平均克拉默-罗下限为 9 ± 1%。点分辨波谱序列用于测量多形性胶质母细胞瘤患者的甘氨酸水平。使用肿瘤质量的水信号获得代谢物浓度。研究表明，一部分人类神经胶质瘤的甘氨酸水平比正常水平升高了 1.5-8 倍。
