THEORETICAL-MODEL FOR WATER DIFFUSION IN TISSUES
THEORETICAL-MODEL FOR WATER DIFFUSION IN TISSUES
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DOI：
10.1002/mrm.1910330516
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发表时间：
1995-05-01
影响因子：
3.3
通讯作者：
GORE, JC
中科院分区：
文献类型：
--
作者：
SZAFER, A;ZHONG, JH;GORE, JC
对水在组织模型中的扩散进行了解析和数值研究。组织被认为是由部分渗透膜（细胞）包围的周期性盒子阵列，包埋在细胞外介质中，细胞内和细胞外扩散系数可能不同。表观扩散系数（ADC）在各向同性和非各向同性组织的表达式推导和Monte Carte模拟比较。计算的ADC与从广泛使用的“快速交换”公式获得的值不一致。细胞内和细胞外T-2弛豫时间的差异ADC和T-2的测量值的影响进行了讨论。一般的分析是专门适用于ADC发生的变化后，缺血性脑损伤组织。据发现，虽然膜影响ADC显着，所观察到的扩散的变化不能是由于降低膜渗透性。它们可能是细胞体积分数、细胞外和细胞内扩散变化的综合作用的结果。
Water diffusion in a tissue model is studied both analytically and numerically. Tissue is regarded as a periodic array of boxes surrounded by partially permeable membranes (cells), embedded in an extracellular medium, intracellular and extracellular diffusion coefficients may differ. Expressions for the apparent diffusion coefficients (ADC) in isotropic and nonisotropic tissues are derived and compared with Monte Carte simulations. Calculated ADCs disagree with values obtained from the widely used ''fast exchange'' formula. Effects of differences between intracellular and extracellular T-2 relaxation times on measured values of ADC and T-2 are discussed. The general analysis is specifically applied to the changes occurring in ADC following ischemic insults to brain tissue. It is found that although membranes affect ADC significantly, the observed changes in diffusion cannot be due to reduced membrane permeabilities. They may result from the combined effect of changes in cellular volume fraction, extracellular and intracellular diffusion.