Model-based analysis of multishell diffusion MR data for tractography: how to get over fitting problems.
Model-based analysis of multishell diffusion MR data for tractography: how to get over fitting problems.
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DOI：
10.1002/mrm.24204
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发表时间：
2012-12
影响因子：
3.3
通讯作者：
Behrens, Timothy E. J.
中科院分区：
文献类型：
--
作者：
Jbabdi, Saad;Sotiropoulos, Stamatios N.;Savio, Alexander M.;Grana, Manuel;Behrens, Timothy E. J.
在这篇文章中，我们强调了一个问题，当使用多个b值在基于模型的分析扩散磁共振数据用于声带成像。在实验数据中经常观察到的非单指数衰减，如果不在模型中考虑，则会导致纤维取向分布的过度拟合。垂直于主取向的额外纤维取向出现，以补偿在较高b值时较慢的表观信号衰减。基于扩散系数的连续Gamma分布，我们对球棒模型提出了一种简单的扩展，它显著地改善了拟合，减少了过拟合。使用活体实验数据，我们表明该模型优于更简单的噪声底板模型，特别是在脑组织之间的界面上，这表明部分体积效应是观察到的非单指数衰减的主要原因。这个模型可能对未来的数据采集策略有帮助，这些策略可能试图将多个贝壳结合起来，以改进对白质和皮质附近纤维方向的估计。
In this article, we highlight an issue that arises when using multiple b-values in a model-based analysis of diffusion MR data for tractography. The non-mono-exponential decay, commonly observed in experimental data, is shown to induce over-fitting in the distribution of fibre orientations when not considered in the model. Extra fibre orientations perpendicular to the main orientation arise to compensate for the slower apparent signal decay at higher b-values. We propose a simple extension to the ball and stick model based on a continuous Gamma distribution of diffusivities, which significantly improves the fitting and reduces the over-fitting. Using in-vivo experimental data, we show that this model outperforms a simpler, noise floor model, especially at the interfaces between brain tissues, suggesting that partial volume effects are a major cause of the observed non-mono-exponential decay. This model may be helpful for future data acquisition strategies that may attempt to combine multiple shells to improve estimates of fibre orientations in white matter and near the cortex.
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