Kreher B W, Schnell S, Mader I, Il'yasov K A, Hennig J, Kiselev V G, Saur D
Medical Physics, Department of Diagnostic Radiology, University Hospital, Freiburg, Germany.
Neuroimage. 2008 Oct 15;43(1):81-9. doi: 10.1016/j.neuroimage.2008.06.023. Epub 2008 Jun 27.
Probability mapping of connectivity is a powerful tool to determine the fibre structure of white matter in the brain. Probability maps are related to the degree of connectivity to a chosen seed area. In many applications, however, it is necessary to isolate a fibre bundle that connects two areas. A frequently suggested solution is to select curves, which pass only through two or more areas. This is very inefficient, especially for long-distance pathways and small areas. In this paper, a novel probability-based method is presented that is capable of extracting neuronal pathways defined by two seed points. A Monte Carlo simulation based tracking method, similar to the Probabilistic Index of Connectivity (PICo) approach, was extended to preserve the directional information of the main fibre bundles passing a voxel. By combining two of these extended visiting maps arising from different seed points, two independent parameters are determined for each voxel: the first quantifies the uncertainty that a voxel is connected to both seed points; the second represents the directional information and estimates the proportion of fibres running in the direction of the other seed point (connecting fibre) or face a third area (merging fibre). Both parameters are used to calculate the probability that a voxel is part of the bundle connecting both seed points. The performance and limitations of this DTI-based method are demonstrated using simulations as well as in vivo measurements.
连通性概率图谱是确定大脑白质纤维结构的有力工具。概率图谱与到选定种子区域的连通程度相关。然而，在许多应用中，有必要分离连接两个区域的纤维束。一种经常被提出的解决方案是选择仅穿过两个或更多区域的曲线。这非常低效，尤其是对于长距离通路和小区域。本文提出了一种基于概率的新方法，该方法能够提取由两个种子点定义的神经通路。一种基于蒙特卡罗模拟的追踪方法，类似于连通性概率指数（PICo）方法，被扩展以保留穿过体素的主要纤维束的方向信息。通过组合来自不同种子点的两个这样的扩展访问图谱，为每个体素确定两个独立参数：第一个参数量化体素与两个种子点都相连的不确定性；第二个参数表示方向信息，并估计沿另一个种子点方向（连接纤维）或朝向第三个区域（合并纤维）运行的纤维比例。这两个参数都用于计算体素是连接两个种子点的纤维束一部分的概率。使用模拟以及体内测量展示了这种基于扩散张量成像（DTI）方法的性能和局限性。
