REALM: Reinforcement Learning-Based Cross-Modal Alignment for Fine-Grained Medical Report Generation
摘要
Automated medical report generation lacks precise correspondences between anatomical regions and their descriptive sentences, limiting clinical accuracy and interpretability. We propose REALM, a data-efficient framework that achieves fine-grained alignment between image regions and report sentences. Our approach uses large language models to automatically annotate sentences with anatomical regions, while a reinforcement learning-based module localizes corresponding visual regions with minimal supervision. Through contrastive learning, we establish explicit alignments between visual regions and textual descriptions. Experiments on IU X-ray and MIMIC-CXR datasets demonstrate superior performance in both language generation metrics (BLEU-4: 0.201 vs 0.181) and clinical accuracy (F1: 0.384 vs 0.373), while reducing dependency on large-scale manual annotations.