Uncovering the time dependent diffusion coefficient in neural tissue with MRI

这个项目的总体目标是揭示 表观扩散系数随时间的变化测量扩散 神经组织的加权磁共振成像(DWI)。而依赖于时间的变化在 扩散系数在之前的许多神经组织研究中都被测量过， 这些变化背后的确切微观结构特征仍不清楚。揭开面纱 这些测量基础上的微观结构可以改善诊断、分期和 许多神经系统疾病的鉴别，否则表现为非特异性的变化 DWI。我们认为扩散中的时间依赖变化主要源于三个 资料来源：轴突平均直径、轴突外间隙的异质性、方向离散度。 在这个项目中，我们建议(1)开发和使用数值模拟来测试 时间依赖扩散对组织微结构的敏感性，(2)验证时间依赖 在不同轴突直径的特定动物模型中扩散系数的变化， 轴突外间隙的异质性和白质的复杂性，以及(3)提供基线 与时间相关的扩散系数的估计和这些测量中的可变性 在健康的人类对照人群中。

The overarching goal of this project is to reveal the microstructural features that underlie the diffusion-time dependent changes in the apparent diffusion coefficient measured diffusion weighted magnetic resonance imaging (DWI) in neural tissue. While time dependent changes in the diffusion coefficient have been measured in numerous previous studies of neural tissue, the exact microstructural characteristics of that underly these changes remain unclear. Uncovering the microstructure that underly these measurements could improve the diagnosis, staging and differentiation of numerous neurological diseases that otherwise show nonspecific changes with DWI. We propose that time dependent changes in diffusion originate primarily from three sources: mean axon diameter, heterogeneity of extra-axonal space, and orientation dispersion. Within this project, we propose to (1) develop and use numerical simulations to test the sensitivity of time dependent diffusion to tissue microstructure, (2) validate time dependent changes in the diffusion coefficient in specific animal models that vary axon diameter, heterogeneity of extra-axonal space, and complexity of white matter, and (3) provide baseline estimates of the time dependent diffusion coefficient and the variability in these measurements in a population of healthy human controls.