Lori N F, Akbudak E, Shimony J S, Cull T S, Snyder A Z, Guillory R K, Conturo T E
Mallinckrodt Institute of Radiology, Washington University School of Medicine, 4525 Scott Avenue, St Louis, MO 63110, USA.
NMR Biomed. 2002 Nov-Dec;15(7-8):494-515. doi: 10.1002/nbm.779.
We present a description, biological results and a reliability analysis for the method of diffusion tensor tracking (DTT) of white matter fiber pathways. In DTT, diffusion-tensor MRI (DT-MRI) data are collected and processed to visualize the line trajectories of fiber bundles within white matter (WM) pathways of living humans. A detailed description of the data acquisition is given. Technical aspects and experimental results are illustrated for the geniculo-calcarine tract with broad projections to visual cortex, occipital and parietal U-fibers, and the temporo-calcarine ventral pathway. To better understand sources of error and to optimize the method, accuracy and precision were analyzed by computer simulations. In the simulations, noisy DT-MRI data were computed that would be obtained for a WM pathway having a helical trajectory passing through gray matter. The error vector between the real and ideal track was computed, and random errors accumulated with the square root of track length consistent with a random-walk process. Random error was most dependent on signal-to-noise ratio, followed by number of averages, pathway anisotropy and voxel size, in decreasing order. Systematic error only occurred for a few conditions, and was most dependent on the stepping algorithm, anisotropy of the surrounding tissue, and non-equal voxel dimensions. Both random and systematic errors were typically below the voxel dimension. Other effects such as track rebound and track recovery also depended on experimental conditions. The methods, biological results and error analysis herein may improve the understanding and optimization of DTT for use in various applications in neuroscience and medicine.
我们对白质纤维束扩散张量追踪（DTT）方法进行了描述、生物学结果分析及可靠性分析。在DTT中，收集并处理扩散张量磁共振成像（DT-MRI）数据，以可视化活体人类白质（WM）通路内纤维束的轨迹线。文中给出了数据采集的详细描述。以广泛投射至视觉皮层的膝状体-距状束、枕叶和顶叶U形纤维以及颞叶-距状腹侧通路为例，阐述了技术方面和实验结果。为了更好地理解误差来源并优化该方法，通过计算机模拟分析了准确性和精确性。在模拟中，计算了具有穿过灰质的螺旋轨迹的WM通路所获得的含噪声DT-MRI数据。计算真实轨迹与理想轨迹之间的误差向量，随机误差随轨迹长度的平方根累积，这与随机游走过程一致。随机误差最主要取决于信噪比，其次依次为平均次数、通路各向异性和体素大小。系统误差仅在少数情况下出现，且最主要取决于步进算法、周围组织的各向异性以及体素尺寸不相等。随机误差和系统误差通常都低于体素尺寸。其他效应，如轨迹反弹和轨迹恢复，也取决于实验条件。本文中的方法、生物学结果和误差分析可能会增进对DTT的理解，并优化其在神经科学和医学各种应用中的使用。
