RadJEPA: Radiology Encoder for Chest X-Rays via Joint Embedding Predictive Architecture

Anas Anwarul Haq Khan, Mariam Husain, Pratik Jalan, Kshitij Sharad Jadhav


Abstract
Vision-language pretraining has driven progress in medical image representation learning, but it depends on paired image-text data and can inherit reporting bias from clinical narratives. We study whether language-free predictive pretraining can produce an image encoder that transfers effectively to radiology report generation. RadJEPA is a chest-X-ray adaptation of I-JEPA, pretrained on approximately 840K unlabeled radiographs using latent context-to-target prediction. Our primary contribution is an extensive empirical evaluation of this language-free encoder for report generation: the frozen image encoder is coupled to a trainable two-layer projector and language decoder, and is also substituted into four established vision-language backbones. Across MIMIC-CXR and IU-Xray, RadJEPA matches or exceeds the evaluated image-only and image-text baselines on lexical, entity-relation, and clinical-label metrics. Controlled MIMIC-only comparisons provide evidence that the predictive objective contributes beyond domain-specific pretraining, while broader comparisons also reflect differences in pretraining data, model capacity, and input resolution. Complementary classification and segmentation experiments assess transfer beyond report generation.
Anthology ID:
2026.findings-emnlp.1419
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
30238–30259
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.1419/
DOI:
10.18653/2026.findings-emnlp.1419
Bibkey:
Cite (ACL):
Anas Anwarul Haq Khan, Mariam Husain, Pratik Jalan, and Kshitij Sharad Jadhav. 2026. RadJEPA: Radiology Encoder for Chest X-Rays via Joint Embedding Predictive Architecture. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 30238–30259, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
RadJEPA: Radiology Encoder for Chest X-Rays via Joint Embedding Predictive Architecture (Khan et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.1419.pdf