Center for Imaging Research, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0583, USA.
NMR Biomed. 2013 Sep;26(9):1152-7. doi: 10.1002/nbm.2929. Epub 2013 Feb 12.
In previous work at 4.7 T, the individual components of biexponential (7) Li transverse (T2 ) spin relaxation in rat brain in vivo were tentatively identified with intra- and extracellular Li. The goal in this work was to estimate Li's compartmental distribution as a function of total Li concentration in brain from the biexponential decays. Here a localized, biexponential (7) Li T2 MR spin-relaxation study with isotopically enriched (7) LiCl is reported in rat brain in vivo at 7 T. Additionally, a simple linear interpolation using the biexponential T2 values to estimate intracellular Li from individual monoexponential T2 decays was assessed. Intracellular T2 was 14.8 ± 4.3 ms and extracellular T2 was 295 ± 61 ms. The fraction of intracellular brain Li ranged from 37.3 to 64.8% (mean 54.5 ± 6.7%) and did not correlate with total Li concentration. The estimated intracellular Li concentration ranged from 47 to 80% (mean 68.3 ± 8.5%) of the total brain Li concentration and was highly correlated with it. The monoexponential estimates of the intracellular-Li fractions and derived concentrations averaged about 15% higher than the corresponding biexponential estimates. This work supports the previous conclusion that a large fraction of Li in the brain is within the intracellular compartment.
在之前的 4.7T 研究中，活体大鼠脑内双指数（7）Li 横向（T2）自旋弛豫的各个分量被初步鉴定为细胞内和细胞外 Li。本研究的目的是从双指数衰减中估计 Li 的区室分布作为脑内总 Li 浓度的函数。本研究在 7T 下利用同位素富集（7）LiCl 进行了局部双指数（7）Li T2 MR 自旋弛豫研究。此外，还评估了使用双指数 T2 值通过单个单指数 T2 衰减来简单线性插值估计细胞内 Li 的方法。细胞内 T2 为 14.8 ± 4.3ms，细胞外 T2 为 295 ± 61ms。脑内 Li 的细胞内分数范围为 37.3%至 64.8%（平均值 54.5 ± 6.7%），与总 Li 浓度无关。估计的细胞内 Li 浓度范围为总脑 Li 浓度的 47%至 80%（平均值 68.3 ± 8.5%），与总 Li 浓度高度相关。细胞内 Li 分数和衍生浓度的单指数估计值平均比相应的双指数估计值高约 15%。这项工作支持了之前的结论，即大脑中很大一部分 Li 位于细胞内区室。
