Cost function masking during normalization of brains with focal lesions: still a necessity?
Cost function masking during normalization of brains with focal lesions: still a necessity?
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DOI：
10.1016/j.neuroimage.2010.06.003
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发表时间：
2010-10-15
期刊：
影响因子：
5.7
通讯作者：
Beeson, Pelagie M.
中科院分区：
文献类型：
--
作者：
Andersen, Sarah M.;Rapcsak, Steven Z.;Beeson, Pelagie M.
尽管大脑图像的标准化对于分析个体的结构损伤至关重要，但局灶性病变导致的组织损失对可用的标准化算法提出了挑战。直到最近，成本函数掩蔽（cost function masking），正如所倡导的那样，仍然是克服在正常化受损大脑时遇到的困难的公认方法。然而，SPM5 中标准化统一分割方法的开发提供了另一种选择。证明这种方法产生的标准化结果没有成本函数掩蔽，当使用所研究的相同模拟病变进行测试时，该结果似乎对病变效应具有鲁棒性。本研究试图证实这种方法在因血管事件而造成局灶性损伤的大脑中的有效性。为此，我们在 49 幅慢性中风的大脑图像中检查了使用统一分割（有或没有成本函数掩蔽）的归一化结果。使用两种方法（精确和粗略绘制病变边界）创建病变掩模，并使用平滑和非平滑版本的掩模实现归一化。我们发现，与掩蔽归一化相比，在变形场位移和体素强度差异方面，未能采用成本函数掩蔽在真实和模拟病变中产生的结果不太准确。此外，相对于所有四种掩蔽条件，未掩蔽标准化导致显着低估病变体积，特别是对于病变较大的患者。总而言之，这些发现表明，在标准化慢性梗塞的大脑图像时，成本函数掩蔽仍然是必要的。
Although normalization of brain images is critical to the analysis of structural damage across individuals, loss of tissue due to focal lesions presents challenges to the available normalization algorithms. Until recently, cost function masking, as advocated by, was the accepted method to overcome difficulties encountered when normalizing damaged brains; however, development of the unified segmentation approach for normalization in SPM5 offered an alternative. demonstrated this approach produced normalization results without cost function masking that appeared to be robust to lesion effects when tested using the same simulated lesions studied by. The present study sought to confirm the validity of this approach in brains with focal damage due to vascular events. To do so, we examined outcomes of normalization using unified segmentation with and without cost function masking in 49 brain images with chronic stroke. Lesion masks were created using two approaches (precise and rough drawings of lesion boundaries), and normalization was implemented with both smoothed and unsmoothed versions of the masks. We found that failure to employ cost function masking produced less accurate results in real and simulated lesions, compared to masked normalization, both in terms of deformation field displacement and voxelwise intensity differences. Additionally, unmasked normalization led to significant underestimation of lesion volume relative to all four masking conditions, especially in patients with large lesions. Taken together, these findings suggest cost function masking is still necessary when normalizing brain images with chronic infarcts.
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