CCS: Clinical Consensus Selection for Radiology Report Generation

Publications

May 29, 2026·

Xi Zhang

Yingshu Li

Zaiqiao Meng

Jake Lever

Edmond S. L. Ho

· 2 min read

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Abstract

Radiology report generation (RRG) is commonly formulated as a single-path generation task, where a multimodal large language model (MLLM) produces one decoded report as the final output. While recent progress has largely been driven by scaling training data, model capacity, and retrieval mechanisms, improving report quality at inference time remains underexplored. In this work, we observe that fixed radiology MLLMs often generate clinically stronger reports elsewhere in their candidate pool than the one selected by default decoding, suggesting that inference-time decision making remains an overlooked bottleneck. To address this, we propose Clinical Consensus Selection (CCS), a decoder-agnostic inference-time selection framework that samples multiple candidate reports and selects the one with the highest clinical consensus across the rollout pool. CCS unifies text-based utilities with a radiology-adapted utility computed by an image–report-trained multimodal embedder, which measures candidate agreement beyond surface-level textual similarity. Across three datasets and multiple radiology MLLMs, CCS consistently improves inference-time performance over single-path decoding and generic Best-of-N baselines, with particularly clear gains on clinical metrics. Further analysis shows that image-grounded utility forms a selection axis distinct from textual consensus and that substantial headroom remains for improving RRG at inference time.

Type

Preprint

For the latest updates and details, visit the CCS Project Website.

Why CCS? 🔬

Most radiology MLLMs commit to a single decoded report token by token, so one unfavourable step can omit a finding or assert one unsupported by the image, with no way to recover. Yet a fixed model often places clinically stronger reports elsewhere in its candidate pool — the bottleneck is not what the model can generate, but which candidate it commits to.

How CCS Works ⚙️

Clinical Consensus Selection (CCS) is a reference-free, decoder-agnostic inference-time framework that reframes RRG as candidate selection — no retraining or extra parameters.

Rollout sampling: draw N candidate reports from the radiology MLLM via stochastic decoding.
Textual consensus utility: repurpose report-evaluation metrics as reference-free pairwise agreement scores.
Image-grounded utility: measure candidate agreement with Qwen3-VL-Embed, a multimodal embedder adapted on image–report pairs, capturing clinical agreement beyond surface text.
Highest-consensus selection: return the candidate with the highest mean pairwise consensus over the pool.

Key Contributions ✨

Inference-time perspective: We show candidate pools routinely contain reports with higher clinical reliability and consistency than single-path outputs.
CCS framework: A decoder-agnostic Best-of-N method that aggregates pairwise clinical consensus using both textual and image–report-adapted multimodal utilities.
Consistent gains: Across three datasets and multiple radiology MLLMs, CCS improves RRG at inference time and identifies image-grounded utility as a distinct selection axis.

Main Results 📈

On MIMIC-CXR, CCS improves all radiology-specific metrics over Sampling (e.g. RadGraph-F1 0.1989 → 0.2134, CheXbert-F1⁵ 0.5041 → 0.5370), with gains statistically significant (p < 0.05). Unlike generic Best-of-N selectors (Self-Certainty, ModeX) that give inconsistent or negative clinical gains, CCS improves consistently across all backbones and datasets.

Analysis 📊

Per-label F1 shows CCS recovers abnormal findings that text-only consensus suppresses — confirming that image-grounded utility is a selection axis distinct from textual consensus, with substantial headroom still remaining.

Case Study 🔍

On a real MIMIC-CXR case, single-path decoding asserts factual errors (false “clear lungs”, mislocalised catheter), whereas CCS selects a more image-grounded report (CheXbert-F1⁵ 1.0000 vs Sampling 0.5000).

BibTeX 📚

@article{zhang2026ccsclinicalconsensusselection,
      title={CCS: Clinical Consensus Selection for Radiology Report Generation}, 
      author={Xi Zhang and Yingshu Li and Zaiqiao Meng and Jake Lever and Edmond S. L. Ho},
      year={2026},
      eprint={2605.30131},
      archivePrefix={arXiv},
      primaryClass={cs.CL},
      url={https://arxiv.org/abs/2605.30131}, 
}