Multi-Granularity Cross-modal Alignment for Generalized Medical Visual Representation Learning

TL;DR

This paper introduces a multi-granularity cross-modal alignment framework that leverages semantic correspondences at multiple levels to improve generalized medical visual representation learning from radiology reports.

Contribution

It proposes a novel MGCA framework that aligns medical images and reports at pathological, instance, and disease levels, enhancing representation learning beyond local supervision.

Findings

Outperforms existing methods on seven medical image datasets.

Improves performance in classification, detection, and segmentation tasks.

Demonstrates stable and superior results across various tasks.

Abstract

Learning medical visual representations directly from paired radiology reports has become an emerging topic in representation learning. However, existing medical image-text joint learning methods are limited by instance or local supervision analysis, ignoring disease-level semantic correspondences. In this paper, we present a novel Multi-Granularity Cross-modal Alignment (MGCA) framework for generalized medical visual representation learning by harnessing the naturally exhibited semantic correspondences between medical image and radiology reports at three different levels, i.e., pathological region-level, instance-level, and disease-level. Specifically, we first incorporate the instance-wise alignment module by maximizing the agreement between image-report pairs. Further, for token-wise alignment, we introduce a bidirectional cross-attention strategy to explicitly learn the matching between fine-grained visual tokens and text tokens, followed by contrastive learning to align them. More important, to leverage the high-level inter-subject relationship semantic (e.g., disease) correspondences, we design a novel cross-modal disease-level alignment paradigm to enforce the cross-modal cluster assignment consistency. Extensive experimental results on seven downstream medical image datasets covering image classification, object detection, and semantic segmentation tasks demonstrate the stable and superior performance of our framework.