LoFi: Location-Aware Fine-Grained Representation Learning for Chest X-ray

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Hauptverfasser: Kang, Myeongkyun, Yang, Yanting, Li, Xiaoxiao
Format: Preprint
Veröffentlicht: 2026
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author Kang, Myeongkyun
Yang, Yanting
Li, Xiaoxiao
author_facet Kang, Myeongkyun
Yang, Yanting
Li, Xiaoxiao
contents Fine-grained representation learning is crucial for retrieval and phrase grounding in chest X-rays, where clinically relevant findings are often spatially confined. However, the lack of region-level supervision in contrastive models and the limited ability of large vision language models to capture fine-grained representations in external validation lead to suboptimal performance on these tasks. To address these limitations, we propose Location-aware Fine-grained representation learning (LoFi), which jointly optimizes sigmoid, captioning, and location-aware captioning losses using a lightweight large language model. The location-aware captioning loss enables region-level supervision through grounding and dense captioning objectives, thereby facilitating fine-grained representation learning. Building upon these representations, we integrate a fine-grained encoder into retrieval-based in-context learning to enhance chest X-ray grounding across diverse settings. Extensive experiments demonstrate that our method achieves superior retrieval and phrase grounding performance on MIMIC-CXR and PadChest-GR.
format Preprint
id arxiv_https___arxiv_org_abs_2603_19451
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle LoFi: Location-Aware Fine-Grained Representation Learning for Chest X-ray
Kang, Myeongkyun
Yang, Yanting
Li, Xiaoxiao
Computer Vision and Pattern Recognition
Artificial Intelligence
Fine-grained representation learning is crucial for retrieval and phrase grounding in chest X-rays, where clinically relevant findings are often spatially confined. However, the lack of region-level supervision in contrastive models and the limited ability of large vision language models to capture fine-grained representations in external validation lead to suboptimal performance on these tasks. To address these limitations, we propose Location-aware Fine-grained representation learning (LoFi), which jointly optimizes sigmoid, captioning, and location-aware captioning losses using a lightweight large language model. The location-aware captioning loss enables region-level supervision through grounding and dense captioning objectives, thereby facilitating fine-grained representation learning. Building upon these representations, we integrate a fine-grained encoder into retrieval-based in-context learning to enhance chest X-ray grounding across diverse settings. Extensive experiments demonstrate that our method achieves superior retrieval and phrase grounding performance on MIMIC-CXR and PadChest-GR.
title LoFi: Location-Aware Fine-Grained Representation Learning for Chest X-ray
topic Computer Vision and Pattern Recognition
Artificial Intelligence
url https://arxiv.org/abs/2603.19451