University of Texas Health Science Center, San Antonio, TX, USA.
Psychiatry Res. 2011 Sep 30;193(3):191-8. doi: 10.1016/j.pscychresns.2011.03.005. Epub 2011 Jul 20.
Studies of white matter (WM) abnormalities in psychiatric and neurological disorders often use the analysis package Tract-Based Spatial Statistics (TBSS). However, with small samples and/or subtle effects, a study using the standard TBSS approach can be underpowered. For such cases, a new method is presented that summarizes global differences between TBSS-derived fractional anisotropy (FA) images with a single paired t-statistic, estimating the degrees of freedom using spatial autocorrelation. The sensitivity of the method is demonstrated by using well-known aging effects on FA as a proxy for disease effects. Sixty healthy subjects were divided equally into younger- (YA), middle- (MA), and older-aged (OA) groups and significant global differences were demonstrated in the YA versus OA (all N ≥ 4, FA difference≈0.023), MA versus OA (all N≥4, FA difference≈0.017), and YA versus MA (FA difference≈0.005 at N=20) comparisons. In contrast, no significant difference could be detected in the YA versus MA comparison using voxelwise TBSS analysis with the full sample (N=20 per group). This method should facilitate localizing analyses in the direction of a proven group difference while providing clinically relevant information about pathophysiologic processes globally affecting WM.
研究表明，在精神和神经紊乱方面，对脑白质（WM）异常的研究通常使用基于束路径的空间统计学（TBSS）分析包。然而，对于小样本量和/或细微效应的研究，使用标准 TBSS 方法可能会因功效不足而受到限制。对于这种情况，本文提出了一种新的方法，它使用单个配对 t 统计量来总结 TBSS 衍生的各向异性分数（FA）图像之间的全局差异，使用空间自相关来估计自由度。该方法的灵敏度通过使用众所周知的 FA 老化效应作为疾病效应的替代指标来证明。将 60 名健康受试者平均分为年轻组（YA）、中年组（MA）和老年组（OA），在 YA 与 OA（所有 N≥4，FA 差异≈0.023）、MA 与 OA（所有 N≥4，FA 差异≈0.017）和 YA 与 MA（在 N=20 时 FA 差异≈0.005）比较中，均显示出明显的全局差异。相比之下，在使用全样本（每组 N=20）的基于体素 TBSS 分析中，在 YA 与 MA 比较中无法检测到显著差异。该方法应该有助于在已证实的组间差异方向上进行定位分析，同时提供关于整体影响 WM 的病理生理过程的临床相关信息。
