Local contrastive loss with pseudo-label based self-training for semi-supervised medical image segmentation.

Supervised deep learning-based methods yield accurate results for medical image segmentation. However, they require large labeled datasets for this, and obtaining them is a laborious task that requires clinical expertise. Semi/self-supervised learning-based approaches address this limitation by exploiting unlabeled data along with limited annotated data. Recent self-supervised learning methods use contrastive loss to learn good global level representations from unlabeled images and achieve high performance in classification tasks on popular natural image datasets like ImageNet. In pixel-level prediction tasks such as segmentation, it is crucial to also learn good local level representations along with global representations to achieve better accuracy. However, the impact of the existing local contrastive loss-based methods remains limited for learning good local representations because similar and dissimilar local regions are defined based on random augmentations and spatial proximity; not based on the semantic label of local regions due to lack of large-scale expert annotations in the semi/self-supervised setting. In this paper, we propose a local contrastive loss to learn good pixel level features useful for segmentation by exploiting semantic label information obtained from pseudo-labels of unlabeled images alongside limited annotated images with ground truth (GT) labels. In particular, we define the proposed contrastive loss to encourage similar representations for the pixels that have the same pseudo-label/GT label while being dissimilar to the representation of pixels with different pseudo-label/GT label in the dataset. We perform pseudo-label based self-training and train the network by jointly optimizing the proposed contrastive loss on both labeled and unlabeled sets and segmentation loss on only the limited labeled set. We evaluated the proposed approach on three public medical datasets of cardiac and prostate anatomies, and obtain high segmentation performance with a limited labeled set of one or two 3D volumes. Extensive comparisons with the state-of-the-art semi-supervised and data augmentation methods and concurrent contrastive learning methods demonstrate the substantial improvement achieved by the proposed method. The code is made publicly available at https://github.com/krishnabits001/pseudo_label_contrastive_training.

Chaitanya K ，Erdil E ，Karani N ，Konukoglu E ... -  《-》

HPFG: semi-supervised medical image segmentation framework based on hybrid pseudo-label and feature-guiding.

Semi-supervised learning methods have been attracting much attention in medical image segmentation due to the lack of high-quality annotation. To cope with the noise problem of pseudo-label in semi-supervised medical image segmentation and the limitations of contrastive learning applications, we propose a semi-supervised medical image segmentation framework, HPFG, based on hybrid pseudo-label and feature-guiding, which consists of a hybrid pseudo-label strategy and two different feature-guiding modules. The hybrid pseudo-label strategy uses the CutMix operation and an auxiliary network to enable the labeled images to guide the unlabeled images to generate high-quality pseudo-label and reduce the impact of pseudo-label noise. In addition, a feature-guiding encoder module based on feature-level contrastive learning is designed to guide the encoder to mine useful local and global image features, thus effectively enhancing the feature extraction capability of the model. At the same time, a feature-guiding decoder module based on adaptive class-level contrastive learning is designed to guide the decoder in better extracting class information, achieving intra-class affinity and inter-class separation, and effectively alleviating the class imbalance problem in medical datasets. Extensive experimental results show that the segmentation performance of the HPFG framework proposed in this paper outperforms existing semi-supervised medical image segmentation methods on three public datasets: ACDC, LIDC, and ISIC. Code is available at https://github.com/fakerlove1/HPFG .

Li F ，Jiang A ，Li M ，Xiao C ，Ji W ... -  《-》

Semi-Supervised Representation Learning for Segmentation on Medical Volumes and Sequences.

Chen Z ，Zhuo W ，Wang T ，Cheng J ，Xue W ，Ni D ... -  《-》

RCPS: Rectified Contrastive Pseudo Supervision for Semi-Supervised Medical Image Segmentation.

Zhao X ，Qi Z ，Wang S ，Wang Q ，Wu X ，Mao Y ，Zhang L ... -  《-》

Semi-supervised liver segmentation based on local regions self-supervision.

Lou Q ，Lin T ，Qian Y ，Lu F ... -  《-》