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arXiv 2209.09641cs.CV
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基于边际标签平滑的分割网络校准

Calibrating Segmentation Networks with Margin-based Label Smoothing

ÉTS Montréal(蒙特利尔高等工程技术学院);International Laboratory on Learning Systems (ILLS)(国际学习系统实验室);MILA(米拉研究所);CNRS(法国国家科学研究中心);Université Paris-Saclay(巴黎萨克雷大学);CentraleSupélec(中央理工-高等电力学院);Universitat Pompeu Fabra(庞培法布拉大学);Centre de Recherche du Centre Hospitalier de l’Université de Montréal (CRCHUM)(蒙特利尔大学医院研究中心)

Balamurali Murugesan, Bingyuan Liu, Adrian Galdran, Ismail Ben Ayed, Jose Dolz

AI总结:

针对深度分割网络校准不佳、预测过度自信的问题,提出基于不等式约束的可调控边际标签平滑方法,在医学图像分割任务上实现了校准性能与判别性能的双重提升。

摘要:

尽管深度神经网络推动视觉识别任务取得了不可否认的进展,但近期有证据表明这些模型的校准效果不佳,会导致预测结果过度自信。训练过程中最小化交叉熵损失的标准做法会促使预测的softmax概率与独热标签分配相匹配。然而,这会使得正确类别的softmax前激活值远大于其余类别的激活值,从而加剧校准偏差问题。分类领域的近期研究表明,隐式或显式最大化预测熵的损失函数可实现当前最优的校准性能。尽管已有这些发现,但这类损失函数在医学图像分割网络校准这一相关任务中的影响仍未被探究。在本研究中,我们从约束优化的统一视角对当前最优的校准损失进行了分析。具体而言,这些损失可被视为对logit距离施加等式约束的线性惩罚项(或拉格朗日项)的近似。这揭示了这类底层等式约束的一个重要局限:其产生的梯度会持续向无信息解的方向推动,可能导致在基于梯度的优化过程中无法在模型的判别性能与校准效果之间达成最佳平衡。根据我们的观察,我们提出了一种基于不等式约束的简单且灵活的泛化方法,该方法对logit距离施加可调控的边际。我们在多个公开医学图像分割基准数据集上开展了综合实验,结果表明,我们的方法在网络校准方面取得了全新的最优结果,同时判别性能也得到了提升。

英文摘要:

Despite the undeniable progress in visual recognition tasks fueled by deep neural networks, there exists recent evidence showing that these models are poorly calibrated, resulting in over-confident predictions. The standard practices of minimizing the cross entropy loss during training promote the predicted softmax probabilities to match the one-hot label assignments. Nevertheless, this yields a pre-softmax activation of the correct class that is significantly larger than the remaining activations, which exacerbates the miscalibration problem. Recent observations from the classification literature suggest that loss functions that embed implicit or explicit maximization of the entropy of predictions yield state-of-the-art calibration performances. Despite these findings, the impact of these losses in the relevant task of calibrating medical image segmentation networks remains unexplored. In this work, we provide a unifying constrained-optimization perspective of current state-of-the-art calibration losses. Specifically, these losses could be viewed as approximations of a linear penalty (or a Lagrangian term) imposing equality constraints on logit distances. This points to an important limitation of such underlying equality constraints, whose ensuing gradients constantly push towards a non-informative solution, which might prevent from reaching the best compromise between the discriminative performance and calibration of the model during gradient-based optimization. Following our observations, we propose a simple and flexible generalization based on inequality constraints, which imposes a controllable margin on logit distances. Comprehensive experiments on a variety of public medical image segmentation benchmarks demonstrate that our method sets novel state-of-the-art results on these tasks in terms of network calibration, whereas the discriminative performance is also improved.

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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