Semi-supervised segmentation of lung CT images based on contrastive learning

Accurate segmentation of lesions in lung CT images remains challenging due to blurred boundaries, small lesion sizes, and the scarcity of annotated data. To address these issues, this paper proposes a semi-supervised contrastive learning framework with a novel multiple attention UNet (MA-UNet) for lung CT image segmentation. The MA-UNet integrates a dual-attention module (DAM) and attention gates (AGs) to enhance spatial-channel feature refinement and boundary sensitivity. The DAM captures global context and channel-wise dependencies, while the AG emphasizes lesion-related features. Furthermore, residual blocks are used to improve gradient propagation and computational efficiency. To overcome limited annotations, we propose a contrastive learning framework that can fully utilize both labeled and unlabeled data to improve segmentation accuracy. To verify the validity of the methods and parameters design in this paper, we systematically carry out multiple ablation experiments. The experimental results show that the Dice, MIoU and Recall scores of MA-UNet based on comparative learning with only 1/2 ratio of labeled data are 78.41%, 88.78% and 91.79%, respectively, which are close to its supervised segmentation model, which effectively overcomes the problem of lack of labeled data.