Dept. of Psychiatry, Psychotherapy, and Psychosomatics, University of Halle (Saale), Germany.
Schizophr Res. 2011 Oct;132(1):91-6. doi: 10.1016/j.schres.2011.07.023. Epub 2011 Aug 5.
Neuroimaging techniques such as magnetization transfer imaging allow the detection of microstructural alterations of tissue, and for this reason have been applied to the study of disorders such as schizophrenia. However, they are also sensitive to partial volume effects arising from mixed compartments, such as those comprising cerebral spinal fluid, which makes separate evaluation of volumetric and structural alterations difficult. Ensuing regional differences in the distribution of data and signal-to-noise ratio add further potential bias to their assessment. In the present study we simultaneously applied tissue segmentation, statistical imputation, and nonparametric inference to address these issues and improve the validity of statistical inference. In a case study of N=32 schizophrenic patients matched to the same number of controls, we compared a standard voxel-based analysis with one supplemented by the imputation technique. We were able to replicate significant results in the imputed analysis and even extend them in the areas not excluded by excessive partial volume effects. Application of segmentation algorithms in this dataset also suggested that partial volume effects from spinal fluid potentially affect inference in most cortical gray matter, unless remedial steps are undertaken. Refined imputation methods may be particularly attractive in future research settings characterized by large samples and the availability of adequate computational resources.
神经影像学技术，如磁化传递成像，可用于检测组织的微观结构改变，因此已被应用于精神分裂症等疾病的研究。然而，它们也对来自混合隔室（如包含脑脊髓液的隔室）的部分体积效应敏感，这使得对体积和结构改变的单独评估变得困难。随后的数据分布和信噪比的区域差异进一步增加了其评估的潜在偏差。在本研究中，我们同时应用组织分割、统计插补和非参数推断来解决这些问题，提高统计推断的有效性。在一项对 32 名精神分裂症患者与相同数量的对照组进行的病例研究中，我们比较了标准体素分析和补充插补技术的分析。我们能够在插补分析中复制到显著的结果，甚至在不受过度部分体积效应排除的区域扩展它们。在这个数据集上应用分割算法还表明，脑脊液的部分体积效应可能会影响到大多数皮质灰质的推断，除非采取补救措施。在具有大样本和足够计算资源的未来研究环境中，细化的插补方法可能特别有吸引力。
