Diffusion in compartmental systems. I. A comparison of an analytical model with simulations
Diffusion in compartmental systems. I. A comparison of an analytical model with simulations
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DOI：
10.1002/mrm.10557
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发表时间：
2003-09-01
影响因子：
3.3
通讯作者：
Lebrfritz, D
中科院分区：
文献类型：
--
作者：
Meier, C;Dreher, W;Lebrfritz, D
本文研究了微观组织参数影响扩散加权 MR 实验信号衰减的方式。使用 Karger 方程强调了跨膜水通量对信号衰减的影响，该方程根据细胞内和细胞外扩散的细胞边界限制进行了修改。这种分析方法与由两个隔室组成的组织模型的蒙特卡罗模拟进行了广泛的比较。结果表明，扩散加权 MR 方法为估计细胞内交换时间提供了独特的工具。检查了体内数据的适用性限制。结果表明，细胞内交换时间强烈依赖于细胞的大小，导致体内数据存在明显的扩散时间依赖性。因此，具有平均交换时间的两室系统的分析模型不足以解释在大范围 b 值下体内测量的信号曲线。此外，不同扩散加权方法获得的多指数信号曲线的差异可以通过跨膜水通量的影响来解释。 (C) 2003 Wiley-Liss, Inc.
This article examines the way in which microscopic tissue parameters affect the signal attenuation of diffusion-weighted MR experiments. The influence of transmembrane water flux on the signal decay is emphasized using the Karger equations, which are modified with respect to the cellular boundary restrictions for intra- and extracellular diffusion. This analytical approach is extensively compared to Monte-Carlo simulations for a tissue model consisting of two compartments. It is shown that diffusion-weighted MR methods provide a unique tool for estimation of the intracellular exchange time. Restrictions of applicability to in vivo data are examined. It is shown that the intracellular exchange time strongly depends on the size of a cell, leading to an apparent diffusion time dependence for in vivo data. Hence, an analytical model of a two-compartment system with an averaged exchange time is inadequate for the interpretation of signal curves measured in vivo over large ranges of b-values. Furthermore, differences of multiexponential signal curves, as obtained by different methods of diffusion weighting, can be explained by the influence of transmembrane water flux. (C) 2003 Wiley-Liss, Inc.