arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2302.01735cs.CVcs.AIcs.LGeess.IV
收藏

重新思考半监督医学图像分割:一个方差缩减的视角

Rethinking Semi-Supervised Medical Image Segmentation: A Variance-Reduction Perspective

Yale University(耶鲁大学);University of Oxford(牛津大学);University of Science and Technology of China(中国科学技术大学)

Chenyu You, Weicheng Dai, Yifei Min, Fenglin Liu, David A. Clifton, S Kevin Zhou, Lawrence Hamilton Staib, James S Duncan

AI总结:

针对医学图像半监督分割中对比学习易致模型崩溃的问题,提出基于方差缩减估计与分层群理论的ARCO框架,在八个基准上显著优于现有方法。

摘要:

对于医学图像分割,对比学习是当前的主流实践,它通过对比语义上相似和不相似的样本对来提升视觉表征的质量。这一方法基于以下观察:在无法获取真实标签的情况下,若能采样到具有真正不同解剖特征的负样本,可以显著提升性能。然而在现实中,这些样本可能来自相似的解剖区域,且模型可能难以区分少数尾部类别的样本,使得尾部类别更容易被误分类,这两者通常会导致模型崩溃。在本文中,我们提出了ARCO,一个结合分层群论的半监督对比学习(CL)框架,用于医学图像分割。具体而言,我们首先提出基于方差缩减估计的概念来构建ARCO,并证明某些方差缩减技术在标签极度有限的像素/体素级分割任务中尤为有益。此外,我们从理论上证明了这些采样技术在方差缩减方面具有通用性。最后,我们在八个基准(即五个2D/3D医学和三个语义分割数据集)及不同标签设置下实验验证了我们的方法,且我们的方法始终优于最先进的半监督方法。此外,我们用这些采样技术增强了CL框架,并展示出相比以往方法的显著提升。我们相信,通过量化当前自监督目标在完成此类具有挑战性的安全关键任务时的局限性,我们的工作是迈向半监督医学图像分割的重要一步。

英文摘要:

For medical image segmentation, contrastive learning is the dominant practice to improve the quality of visual representations by contrasting semantically similar and dissimilar pairs of samples. This is enabled by the observation that without accessing ground truth labels, negative examples with truly dissimilar anatomical features, if sampled, can significantly improve the performance. In reality, however, these samples may come from similar anatomical regions and the models may struggle to distinguish the minority tail-class samples, making the tail classes more prone to misclassification, both of which typically lead to model collapse. In this paper, we propose ARCO, a semi-supervised contrastive learning (CL) framework with stratified group theory for medical image segmentation. In particular, we first propose building ARCO through the concept of variance-reduced estimation and show that certain variance-reduction techniques are particularly beneficial in pixel/voxel-level segmentation tasks with extremely limited labels. Furthermore, we theoretically prove these sampling techniques are universal in variance reduction. Finally, we experimentally validate our approaches on eight benchmarks, i.e., five 2D/3D medical and three semantic segmentation datasets, with different label settings, and our methods consistently outperform state-of-the-art semi-supervised methods. Additionally, we augment the CL frameworks with these sampling techniques and demonstrate significant gains over previous methods. We believe our work is an important step towards semi-supervised medical image segmentation by quantifying the limitation of current self-supervision objectives for accomplishing such challenging safety-critical tasks.

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。

↑