Non-equivalent images and pixels: Confidence-aware resampling with meta-learning mixup for polyp segmentation

Automatic segmentation of polyp regions in endoscope images is essential for the early diagnosis and surgical planning of colorectal cancer. Recently, deep learning-based approaches have achieved remarkable progress for polyp segmentation, but they are at the expense of laborious large-scale pixel-wise annotations. In addition, these models treat samples equally, which may cause unstable training due to polyp variability. To address these issues, we propose a novel Meta-Learning Mixup (MLMix) data augmentation method and a Confidence-Aware Resampling (CAR) strategy for polyp segmentation. MLMix adaptively learns the interpolation policy for mixup data in a data-driven way, thereby transferring the original soft mixup label to a reliable hard label and enriching the limited training dataset. Considering the difficulty of polyp image variability in segmentation, the CAR strategy is proposed to progressively select relatively confident images and pixels to facilitate the representation ability of model and ensure the stability of the training procedure. Moreover, the CAR strategy leverages class distribution prior knowledge and assigns different penalty coefficients for polyp and normal classes to rebalance the selected data distribution. The effectiveness of the proposed MLMix data augmentation method and CAR strategy is demonstrated through comprehensive experiments, and our proposed model achieves state-of-the-art performance with 87.450% dice on the EndoScene test set and 86.453% dice on the wireless capsule endoscopy (WCE) polyp dataset.