Center for Magnetic Resonance Research and Department of Radiology, University of Minnesota, Minneapolis, Minnesota, USA.
Magn Reson Med. 2018 Jun;79(6):2896-2901. doi: 10.1002/mrm.26969. Epub 2017 Oct 17.
To measure the apparent diffusion coefficients (ADC) of five main metabolites in the human brain at 3T with PRESS and STEAM, avoiding measurement biases because of cross-terms. Cross-terms arise from interactions between slice-selection and spoiler gradients in the localized spectroscopy sequence and the diffusion gradients.
Diffusion-weighted spectra were acquired from the prefrontal cortex in five healthy subjects using STEAM (echo time [TE]/mixing time [TM]/pulse repetition time [TR] = 21.22/105/3000 ms, b-values = 0 and 3172 s/mm ) and PRESS (TE/TR = 54.2/3000 ms, b-values = 0 and 2204 s/mm ). Diffusion weighting was applied using bipolar gradients in three orthogonal directions. Post-processed spectra were analyzed with LCModel, and the trace/3 ADC values were calculated.
Comparable trace/3 ADC values (0.14-0.18 µm /ms) were obtained for five main metabolites with both methods. These metabolites were quantified with Cramér-Rao lower bounds below 15%.
The ADC values of the five main metabolites were successfully measured in the human brain at 3T with eliminated directional dependence. Both STEAM and PRESS can be used to probe the diffusivity of metabolites in normal brain and various pathologies on the clinical scanner with slightly higher precision achieved with STEAM for glutamate and myo-inositol. Magn Reson Med 79:2896-2901, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
在 3T 下使用 PRESS 和 STEAM 测量人脑中五种主要代谢物的表观扩散系数（ADC），避免因交叉项而产生的测量偏差。交叉项源于局灶性波谱序列中层面选择和扰相梯度与扩散梯度之间的相互作用。
使用 STEAM（回波时间 [TE]/混合时间 [TM]/脉冲重复时间 [TR] = 21.22/105/3000 ms，b 值 = 0 和 3172 s/mm ）和 PRESS（TE/TR = 54.2/3000 ms，b 值 = 0 和 2204 s/mm ）从五名健康受试者的前额叶皮层采集扩散加权光谱。扩散加权在三个正交方向上使用双极梯度。使用 LCModel 分析后处理光谱，并计算出迹线/3 ADC 值。
两种方法均获得了五种主要代谢物相似的迹线/3 ADC 值（0.14-0.18 µm /ms）。这些代谢物的定量 Cramér-Rao 下限低于 15%。
成功消除了方向依赖性，在 3T 下测量了人脑中五种主要代谢物的 ADC 值。STEAM 和 PRESS 均可用于在临床扫描仪上探测正常脑和各种病变中代谢物的扩散性，STEAM 对谷氨酸和肌醇的测量精度略高。磁共振医学 79:2896-2901, 2018. © 2017 国际磁共振学会。
