Quirk James D, Bretthorst G Larry, Duong Timothy Q, Snyder Avi Z, Springer Charles S, Ackerman Joseph J H, Neil Jeffrey J
Department of Chemistry, Washington University, St. Louis, Missouri 63110, USA.
Magn Reson Med. 2003 Sep;50(3):493-9. doi: 10.1002/mrm.10565.
This report describes the measurement of water preexchange lifetimes and intra/extracellular content in intact, functioning mammalian brain. Intra- and extracellular water magnetic resonance (MR) signals from rat brain in vivo were quantitatively resolved in the longitudinal relaxation domain following administration of an MR relaxation agent into the extracellular space. The estimated intracellular water content fraction was 81% +/- 8%, and the intra- to extracellular exchange rate constant was 1.81 +/- 0.89 s(-1) (mean +/- SD, N = 9), corresponding to an intracellular water preexchange lifetime of approximately 550 ms. These results provide a temporal framework for anticipating the water exchange regime (fast, intermediate, or slow) underlying a variety of compartment-sensitive measurements. The method also supplies a means by which to evaluate membrane water permeability and intra/extracellular water content serially in intact tissue. The data are obtained in an imaging mode that permits detection of regional variations in these parameters.
本报告描述了在完整、功能正常的哺乳动物大脑中对水预交换寿命以及细胞内/外含量的测量。在向细胞外空间注射磁共振（MR）弛豫剂后，在纵向弛豫域中对大鼠大脑体内的细胞内和细胞外水磁共振（MR）信号进行了定量解析。估计的细胞内水含量分数为81%±8%，细胞内与细胞外的交换速率常数为1.81±0.89 s(-1)（平均值±标准差，N = 9），对应于细胞内水预交换寿命约为550毫秒。这些结果为预测各种对隔室敏感测量所依据的水交换机制（快速、中间或缓慢）提供了一个时间框架。该方法还提供了一种在完整组织中连续评估膜水渗透性和细胞内/外水含量的手段。数据是在成像模式下获得的，该模式允许检测这些参数的区域差异。
