TopoCL: Topological Contrastive Learning for Medical Imaging

TL;DR

TopoCL introduces a topological contrastive learning framework that leverages topological structures in medical images, improving representation quality by integrating topological and visual features through novel augmentations and encoding mechanisms.

Contribution

The paper presents a novel topological contrastive learning framework, TopoCL, that explicitly incorporates topological features into medical image representations, enhancing existing CL methods.

Findings

Achieves an average of +3.26% in classification accuracy across datasets.

Effectively preserves topological properties during augmentation.

Enhances existing contrastive learning methods with topological information.

Abstract

Contrastive learning (CL) has become a powerful approach for learning representations from unlabeled images. However, existing CL methods focus predominantly on visual appearance features while neglecting topological characteristics (e.g., connectivity patterns, boundary configurations, cavity formations) that provide valuable cues for medical image analysis. To address this limitation, we propose a new topological CL framework (TopoCL) that explicitly exploits topological structures during contrastive learning for medical imaging. Specifically, we first introduce topology-aware augmentations that control topological perturbations using a relative bottleneck distance between persistence diagrams, preserving medically relevant topological properties while enabling controlled structural variations. We then design a Hierarchical Topology Encoder that captures topological features through self-attention and cross-attention mechanisms. Finally, we develop an adaptive mixture-of-experts (MoE) module to dynamically integrate visual and topological representations. TopoCL can be seamlessly integrated with existing CL methods. We evaluate TopoCL on five representative CL methods (SimCLR, MoCo-v3, BYOL, DINO, and Barlow Twins) and five diverse medical image classification datasets. The experimental results show that TopoCL achieves consistent improvements: an average gain of +3.26% in linear probe classification accuracy with strong statistical significance, verifying its effectiveness.