DEGRE: Dynamic Gating Ensembles for Trust-Aware Rejection in Medical Image Diagnostics

Abstract

For artificial intelligence to be safely deployed in high-risk domains, it must reliably know its limits. Selective prediction, or learning with a reject option, addresses this by enabling a model to abstain from prediction on inputs it deems unreliable, deferring them to a human expert. While deep ensembles have emerged as a leading approach for uncertainty estimation, their potential is often squandered by rejection methods that rely on static thresholds applied to the mean prediction. In this paper, we propose to learn a dynamic rejection policy directly from the rich behavioral signals of the ensemble itself. Our framework, DEGRE (Dynamic Ensembles Gating for REjection), is a novel meta-learning approach that trains a lightweight gating network on the ensemble’s consensus confidence and its internal disagreement (variance)— to explicitly discriminate between correct and incorrect predictions. Through rigorous evaluation across twelve diverse medical imaging benchmarks (MRI, X-ray, CT), DEGRE significantly advances selective prediction, achieving an average risk-coverage (AURC) reduction of 68.2% compared to the standard ensemble baseline. By providing a more reliable method for a model to recognize its own limitations, this learned, adaptive rejection mechanism paves the way for safer and more responsible integration of AI into critical clinical workflows.

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