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arXiv 2406.02422eess.IVcs.CVcs.LG

IterMask2:基于空间和频域掩码的MRI脑部病灶迭代无监督异常分割

IterMask2: Iterative Unsupervised Anomaly Segmentation via Spatial and Frequency Masking for Brain Lesions in MRI

Imperial College London(帝国理工学院);University of Birmingham(伯明翰大学);University of Oxford(牛津大学)

Ziyun Liang, Xiaoqing Guo, J. Alison Noble, Konstantinos Kamnitsas

AI总结:

针对无监督异常分割中“破坏与重建”范式导致正常区域重建不佳而产生假阳性的问题,提出迭代空间掩码优化策略IterMask2,结合高频图像内容辅助输入,有效改善正常组织重建并提升MRI脑部病灶分割性能。

摘要:

针对病灶分割的无监督异常分割方法在健康受试者图像上训练模型,将其定义为“正常”数据分布。在推理阶段,它们旨在将新图像中的任何病灶分割为“异常”,因为其表现出的模式偏离了“正常”训练数据。现有方法遵循“破坏与重建”范式,故意破坏输入图像,重建使其符合所学“正常”分布,随后基于重建误差分割异常。然而,破坏输入图像不可避免地导致即使正常区域的重建也不理想,从而产生假阳性。为缓解此问题,我们提出了一种新颖的迭代空间掩码优化策略IterMask2。我们迭代地掩码图像区域,进行重建,并基于重建误差更新掩码。此迭代过程逐步添加模型判定为确信正常的区域信息。不断增加的内容指导附近掩码区域的重建,改善这些区域下正常组织的重建效果,减少假阳性。我们还使用高频图像内容作为辅助输入,为掩码区域提供额外结构信息。这进一步增大了正常区域相对于异常区域的重建误差差异,促进后者的分割。我们在多个脑部病灶数据集上进行了实验,证明了该方法的有效性。代码可在https://github.com/ZiyunLiang/IterMask2获取。

英文摘要:

Unsupervised anomaly segmentation approaches to pathology segmentation train a model on images of healthy subjects, that they define as the 'normal' data distribution. At inference, they aim to segment any pathologies in new images as 'anomalies', as they exhibit patterns that deviate from those in 'normal' training data. Prevailing methods follow the 'corrupt-and-reconstruct' paradigm. They intentionally corrupt an input image, reconstruct it to follow the learned 'normal' distribution, and subsequently segment anomalies based on reconstruction error. Corrupting an input image, however, inevitably leads to suboptimal reconstruction even of normal regions, causing false positives. To alleviate this, we propose a novel iterative spatial mask-refining strategy IterMask2. We iteratively mask areas of the image, reconstruct them, and update the mask based on reconstruction error. This iterative process progressively adds information about areas that are confidently normal as per the model. The increasing content guides reconstruction of nearby masked areas, improving reconstruction of normal tissue under these areas, reducing false positives. We also use high-frequency image content as an auxiliary input to provide additional structural information for masked areas. This further improves reconstruction error of normal in comparison to anomalous areas, facilitating segmentation of the latter. We conduct experiments on several brain lesion datasets and demonstrate effectiveness of our method. Code is available at: https://github.com/ZiyunLiang/IterMask2

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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