Diffusion MRI of Complex White Matter and Connectivity

该项目研究了磁共振成像扩散谱成像（DSI）的一种新方法的能力，以绘制复杂的白质结构和人脑中的神经连接。这种能力可能最终使无创地定义大脑的接线图成为可能。目前基于扩散张量磁共振成像（DTI）的方法可以获得在每个位置显示白质平均方向的地图，包括我们自己的研究小组在内的几个研究小组已经设计出了将追踪程序应用于这些方向场的方法，以定义神经通路的大规模轨迹。然而，这种方法有一个严重和基本的限制，即，它无法描述每个组织位置的多个方向。我们最近描述的扩散光谱成像方法克服了这一点，首次提供了在每个图像位置解决整个白质方向分布的能力。这些图提供了对脑白质束的解释和交叉的直接描述。因此，本项目将追求3个主要目标：1 .优化脑白质体内成像的扩散谱成像；验证体外（通过共聚焦显微镜）和体内（通过与患者轴突变性相关）复杂白质结构的扩散光谱成像。通过与人类视觉系统中功能性磁共振成像（fMRI）定义的已知神经通路的相关性，测量大规模白质轨迹DSI计算的准确性。

This project investigates the capacity of a new method of magnetic resonance imaging diffusion spectrum imaging or DSI, to map complex white matter architecture and the neural connectivity in the human brain. This capacity may make it possible ultimately to define the wiring diagram of the brain noninvasively. Current methodology based on diffusion tensor magnetic resonance imaging (DTI) makes it possible to obtain maps that show at each location the mean orientation of white matter, and several research groups including our own, have devised methods to apply tracing procedures to these orientation fields to define the large-scale trajectories of neural pathways. This approach, however, suffers a serious and basic limitation, namely, its inability to describe more than a single orientation at each tissue location. Diffusion spectrum imaging methodology we have recently described overcomes this, providing for the first time an ability to resolve entire distributions white matter orientations at each image location. These maps provide direct descriptions of the interpretation and intersection of cerebral white matter tracts. Accordingly, this project will pursue 3 principal aims: i. To optimize diffusion spectrum imaging for in vivo imaging of cerebral white matter: ii. To validate diffusion spectrum imaging of complex white matter architecture ex vivo (by correlation with confocal microscopy) and in vivo (by correlation with axonal degeneration in patients.), and iii. To measure the accuracy of DSI computation of large scale white matter trajectories, by correlation with known neural pathways defined by functional magnetic resonance imaging (fMRI) in the human visual system.