Department of Psychiatry, University of North Carolina at Chapel Hill, NC, USA.
Neuroimage. 2012 Jan 16;59(2):1315-23. doi: 10.1016/j.neuroimage.2011.08.025. Epub 2011 Aug 26.
Brain morphometric studies often incorporate comparative hemispheric asymmetry analyses of segmented brain structures. In this work, we present evidence that common user guided structural segmentation techniques exhibit strong left-right asymmetric biases and thus fundamentally influence any left-right asymmetry analyses. In this study, MRI scans from ten pediatric subjects were employed for studying segmentations of amygdala, globus pallidus, putamen, caudate, and lateral ventricle. Additionally, two pediatric and three adult scans were used for studying hippocampus segmentation. Segmentations of the sub-cortical structures were performed by skilled raters using standard manual and semi-automated methods. The left-right mirrored versions of each image were included in the data and segmented in a random order to assess potential left-right asymmetric bias. Using shape analysis we further assessed whether the asymmetric bias is consistent across subjects and raters with the focus on the hippocampus. The user guided segmentation techniques on the sub-cortical structures exhibited left-right asymmetric volume bias with the hippocampus displaying the most significant asymmetry values (p<<0.01). The hippocampal shape analysis revealed the bias to be strongest on the lateral side of the body and medial side of the head and tail. The origin of this asymmetric bias is considered to be based in laterality of visual perception; therefore segmentations with any degree of user interaction contain an asymmetric bias. The aim of our study is to raise awareness in the neuroimaging community regarding the presence of the asymmetric bias and its influence on any left-right hemispheric analyses. We also recommend reexamining previous research results in the light of this new finding.
脑形态计量学研究经常将分割脑结构的对比半球不对称分析纳入其中。在这项工作中，我们提供了证据表明，常见的用户引导的结构分割技术表现出强烈的左右不对称偏差，因此从根本上影响任何左右不对称分析。在这项研究中，使用来自十个儿科患者的 MRI 扫描来研究杏仁核、苍白球、壳核、尾状核和侧脑室的分割。此外，还使用了两个儿科和三个成人扫描来研究海马体的分割。使用标准的手动和半自动方法，由熟练的评估者对皮质下结构进行分割。将每个图像的左右镜像版本包含在数据中，并以随机顺序进行分割，以评估潜在的左右不对称偏差。我们进一步使用形状分析评估这种不对称偏差是否在个体和评估者之间是一致的，重点是海马体。皮质下结构的用户引导分割技术表现出左右不对称的体积偏差，其中海马体显示出最显著的不对称值（p<<0.01）。海马体的形状分析显示，这种偏差在身体的外侧和头部和尾部的内侧最强。这种不对称偏差的起源被认为是基于视觉感知的偏侧性；因此，具有任何程度用户交互的分割都包含不对称偏差。我们研究的目的是引起神经影像学社区对不对称偏差的存在及其对任何左右半球分析的影响的关注。我们还建议根据这一新发现重新检查以前的研究结果。
