CONTRAST MECHANISMS IN DIFFUSION WEIGHTED MRI OF BRAIN

该项目的总体目标是提供一个全面和 水在人脑中扩散的定量描述 用来解释水扩散的变化，这种变化发生在 磁共振弥散加权成像的病理条件及其对比度 图像。现在有令人信服的证据表明，水的扩散变化 在各种正常和疾病中具有普遍的兴趣和重要性 条件。我们的目标是明确了解这些变化的基础 发生在中风、癫痫和脑梗塞的扩散加权成像研究中 神经元激活。我们的目标是执行一系列详尽的 水在正常人脑中扩散特性的测量。这些 研究将利用收集成套设备的效率 先进的人体回波平面成像技术数据获取 测量组织水的表观扩散系数(ADC)， 扩散受到限制的程度，以及对程度的评估 扩散各向异性。这些测量将被用来推断 水舱的大小，它们之间的交换率，以及它们的 脑组织中的本征扩散系数。改进型导航仪 还将实现ECHO方法以实现高分辨率 无回波平面采集的扩散图像。测量结果也将 以组织横向腐烂的详细性质为基础 磁化作用允许分解成组分衰减率。 这些所谓弛豫谱的各个分量的图像将 这些信息应该揭示空间上的相关信息 不同水环境的范围和交换。这些测量结果 将补充对ADC在大鼠脑模型中的详细研究 与电生理相关的惊厥和电击 将获得测量结果。观测扩散的门槛 在非常短暂的刺激之后，变化将被确立。我们会 也进行高分辨率Q空间成像的体外制剂 切除大鼠视神经，接受不同的渗透操作，以 评估水量变化和其他变化的影响；我们将 继续我们对水的广泛的计算机和理论建模 在受限和分隔的系统中扩散，以提供定量的 对这些和其他临床观察的解释。因此，我们将 获取解释水扩散行为所需的信息 大脑，以指导患者最佳使用磁共振成像技术 管理和开发组织水扩散模型到更多 详细解释中风和其他疾病患者的MRI变化 条件。

The overall aims of this project are to provide a comprehensive and quantitative description of water diffusion in human brain which can be used to explain the variations in water diffusion that occur in normal and pathological conditions and that produce contrast in diffusion weighted MR images. There is now compelling evidence that water diffusion variations are of general interest and importance in a variety of normal and disease conditions. We aim specifically to understand the basis for the changes that occur in diffusion weighted imaging studies of stroke, seizure and neuronal activation. We aim to perform a series of exhaustive measurements of water diffusion properties in normal human brains. These studies will make use of the efficiency for collecting complete sets of data of advanced echo planar imaging techniques in humans to obtain measurements of the apparent diffusion coefficient (ADC) of tissue water, the degree to which diffusion is restricted, and assessments of the degree of diffusion anisotropy. These measurements will be used to infer the sizes of water compartments, the rates of exchange between them, and their intrinsic diffusion coefficients in brain tissues. Improved navigator echo methods will be implemented as well to permit high resolution diffusion images without echo planar acquisition. Measurements will also be made of the detailed nature of the transverse decay of tissue magnetization to permit the decomposition into component decay rates. Images of individual components of these so-called relaxation spectra will be produced and these should reveal correlative information on the spatial extent and exchange of different water environments. These measurements will be complemented with detailed studies of ADC in rat brain models of seizure and electroshock in which correlative electrophysiological measurements will be acquired. The threshold for observing diffusion changes following very brief stimulations will be established. We will also perform high resolution q space imaging of ex vivo preparations of excised rat optic nerve, subjected to different osmotic manipulations, to evaluate the effects of water volume shifts and other changes; and we will continue our extensive computer and theoretical modeling of water diffusion in restricted and compartmented systems to provide quantitative interpretations of these and other clinical observations. We will thereby obtain the information necessary to interpret water diffusion behavior in the brain, to guide the optimal use of MR imaging techniques in patient management and for developing models of tissue water diffusion to more fully explain the MRI changes seen in patients with stroke and other conditions.