Zhu Tong, Liu Xiaoxu, Connelly Patrick R, Zhong Jianhui
Department of Biomedical Engineering, University of Rochester, Rochester, NY 14642-8648, USA.
Neuroimage. 2008 Apr 15;40(3):1144-56. doi: 10.1016/j.neuroimage.2008.01.016. Epub 2008 Jan 26.
Evaluation of measurement uncertainties (or errors) in diffusion tensor-derived parameters is essential to quantify the sensitivity and specificity of these quantities as potential surrogate biomarkers for pathophysiological processes with diffusion tensor imaging (DTI). Computational methods such as the Monte Carlo simulation have provided insights into characterization of the measurement uncertainty in DTI. However, due to the complexity of real brain data as well as different sources of variations during the image acquisition, a robust estimator for DTI measurement uncertainty in human brain is required. Recent studies have shown that wild bootstrap, a novel nonparametric statistical method, can potentially provide effective estimations of DTI measurement uncertainties in human brain DTI data. In this study, we further optimized the DTI application of the wild bootstrap method for typical clinical applications. We evaluated the validity of wild bootstrap utilizing numerical simulations with different combinations of DTI protocol parameters and wild bootstrap experimental designs, and quantitatively compared estimates of uncertainties from wild bootstrapping with those from Monte Carlo simulations. Our results demonstrate that a wild bootstrap implementation using at least 1000 wild bootstrap iterations with a type II or type III heteroskedasticity consistent covariance matrix estimator provides robust evaluations of most DTI protocols.
评估扩散张量衍生参数中的测量不确定度（或误差）对于量化这些量作为扩散张量成像（DTI）病理生理过程潜在替代生物标志物的敏感性和特异性至关重要。诸如蒙特卡罗模拟等计算方法为表征DTI中的测量不确定度提供了见解。然而，由于真实脑数据的复杂性以及图像采集过程中不同的变异来源，需要一种用于估计人脑DTI测量不确定度的稳健方法。最近的研究表明，野生自助法（一种新颖的非参数统计方法）有可能为人脑DTI数据中的DTI测量不确定度提供有效估计。在本研究中，我们进一步优化了野生自助法在典型临床应用中的DTI应用。我们利用具有不同DTI协议参数组合和野生自助实验设计的数值模拟评估了野生自助法的有效性，并定量比较了野生自助法与蒙特卡罗模拟法的不确定度估计。我们的结果表明，使用至少1000次野生自助迭代以及II型或III型异方差一致协方差矩阵估计器的野生自助法实现，可为大多数DTI协议提供稳健评估。
