DuetFair: Coupling Inter- and Intra-Subgroup Robustness for Fair Medical Image Segmentation

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Main Authors: Tian, Yiqi, Park, Sangjoon, Zeng, Bo, Jin, Pengfei, Oh, Yujin, Li, Quanzheng
Format: Preprint
Published: 2026
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author Tian, Yiqi
Park, Sangjoon
Zeng, Bo
Jin, Pengfei
Oh, Yujin
Li, Quanzheng
author_facet Tian, Yiqi
Park, Sangjoon
Zeng, Bo
Jin, Pengfei
Oh, Yujin
Li, Quanzheng
contents Medical image segmentation models can perform unevenly across subgroups. Most existing fairness methods focus on improving average subgroup performance, implicitly treating each subgroup as internally homogeneous. However, this can hide difficult cases within a subgroup, where high-loss samples are obscured by the subgroup mean. We call this problem \textbf{intra-group hidden failure}. To solve this, we propose \textbf{DuetFair} mechanism, a dual-axis fairness framework that jointly considers inter-subgroup adaptation and intra-subgroup robustness. Based on DuetFair, we introduce \textbf{FairDRO}, which combines distribution-aware mixture-of-experts (dMoE) with subgroup-conditioned distributionally robust optimization (DRO) loss aggregation. This design allows the model to adapt across subgroups while also reducing hidden failures within each subgroup. We evaluate FairDRO on three medical image segmentation benchmarks with varying degrees of within-group heterogeneity. FairDRO achieves the best equity-scaled performance on Harvard-FairSeg and improves worst-case subgroup performance on HAM10000 under both age- and race-based grouping schemes. On the 3D radiotherapy target cohort, FairDRO further improves worst-group Dice by 3.5 points ($\uparrow 6.0\%$) under the tumor-stage grouping and by 4.1 points ($\uparrow 7.4\%$) under the institution grouping over the strongest baseline.
format Preprint
id arxiv_https___arxiv_org_abs_2605_10521
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle DuetFair: Coupling Inter- and Intra-Subgroup Robustness for Fair Medical Image Segmentation
Tian, Yiqi
Park, Sangjoon
Zeng, Bo
Jin, Pengfei
Oh, Yujin
Li, Quanzheng
Computer Vision and Pattern Recognition
Artificial Intelligence
Medical image segmentation models can perform unevenly across subgroups. Most existing fairness methods focus on improving average subgroup performance, implicitly treating each subgroup as internally homogeneous. However, this can hide difficult cases within a subgroup, where high-loss samples are obscured by the subgroup mean. We call this problem \textbf{intra-group hidden failure}. To solve this, we propose \textbf{DuetFair} mechanism, a dual-axis fairness framework that jointly considers inter-subgroup adaptation and intra-subgroup robustness. Based on DuetFair, we introduce \textbf{FairDRO}, which combines distribution-aware mixture-of-experts (dMoE) with subgroup-conditioned distributionally robust optimization (DRO) loss aggregation. This design allows the model to adapt across subgroups while also reducing hidden failures within each subgroup. We evaluate FairDRO on three medical image segmentation benchmarks with varying degrees of within-group heterogeneity. FairDRO achieves the best equity-scaled performance on Harvard-FairSeg and improves worst-case subgroup performance on HAM10000 under both age- and race-based grouping schemes. On the 3D radiotherapy target cohort, FairDRO further improves worst-group Dice by 3.5 points ($\uparrow 6.0\%$) under the tumor-stage grouping and by 4.1 points ($\uparrow 7.4\%$) under the institution grouping over the strongest baseline.
title DuetFair: Coupling Inter- and Intra-Subgroup Robustness for Fair Medical Image Segmentation
topic Computer Vision and Pattern Recognition
Artificial Intelligence
url https://arxiv.org/abs/2605.10521