Between session reproducibility and between subject variability of diffusion MR and tractography measures
Between session reproducibility and between subject variability of diffusion MR and tractography measures
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DOI：
10.1016/j.neuroimage.2006.07.037
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发表时间：
2006-11-15
期刊：
影响因子：
5.7
通讯作者：
Johansen-Berg, H.
中科院分区：
文献类型：
--
作者：
Heiervang, E.;Behrens, T. E. J.;Johansen-Berg, H.
随着弥散束造影越来越多地用于产生定量测量来解决临床问题，表征这些测量的会话间可重复性和受试者间可变性是很重要的。在这里，我们使用8名受试者扫描3次的扩散数据来评估扩散束造影测量的可重复性和可变性。我们使用三种不同的种子定义方法，在每个单独的数据集中使用概率神经束来定义扣带束、锥体束、视神经辐射和胼胝体的胚芽。平均分数各向异性（FA）和平均扩散率（MD）的测量结果比管道体积的测量结果更具重复性。此外，使用两个感兴趣区域（ROI）方法定义的区域比单独使用手动放置种子掩膜定义的区域更具可重复性。对于使用两种ROI方法定义的区域的平均FA，会话间变异系数（CV）均低于5%，受试者间CV低于10%；平均MD间期cv均低于3%，受试者间cv低于8%。我们使用这里发现的变异性测量来计算检测给定大小的FA、MD或束体积变化所需的样本量，无论是在受试者组之间还是受试者内部随时间的变化。最后，我们比较了使用60个扩散编码方向和使用12个方向子集的轨迹成像结果；扩散方向的数量对再现性没有显著影响，但使用较少方向得到的束始终小于使用60个方向数据得到的束。我们认为，12个方向的数据足以重复地定义大束的核心，但可能对较小的路径不太敏感。(c) 2006爱思唯尔公司版权所有。
As diffusion tractography is increasingly used to generate quantitative measures to address clinical questions, it is important to characterise the inter-session reproducibility and inter-subject variability of these measures. Here, we assess the reproducibility and variability of diffusion tractography measures using diffusion data from 8 subjects scanned 3 times. We used probabilistic tractography to define the cingulum bundle, pyramidal tracts, optic radiations and germ of the corpus callosum in each individual data set using three different methods of seed definition. Measures of mean fractional anisotropy (FA) and mean diffusivity (MD) along the tracts were more reproducible than measures of tract volume. Further, tracts defined using a two region of interest (ROI) approach were more reproducible than those defined using manually placed seed masks alone. For mean FA taken from tracts defined using the two ROI approach, inter-session coefficients of variation (CV) were all below 5% and inter-subject CVs were below 10%; for mean MD inter-session, CVs were all below 3% and inter-subject CVs were below 8%. We use the variability measures found here to calculate the sample sizes required to detect changes in FA, MD or tract volume of a given size, either between groups of subjects or within subjects over time. Finally, we compare tractography results using 60 diffusion encoding directions to those found using a subset of 12 directions; the number of diffusion directions did not have a significant effect on reproducibility, but tracts derived using fewer directions were consistently smaller than those derived using 60 direction data. We suggest that 12 direction data are sufficient for reproducibly defining the core of large bundles but may be less sensitive to smaller pathways. (c) 2006 Elsevier Inc. All rights reserved.