Detecting and Evaluating Medical Hallucinations in Large Vision Language Models
Pith reviewed 2026-05-23 23:54 UTC · model grok-4.3
The pith
Med-HallMark benchmark and MediHall Score enable detection and granular evaluation of hallucinations in medical vision-language models.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Med-HallMark supplies the first medical multimodal benchmark with multi-task hallucination support, multifaceted data, and hierarchical categorization; MediHall Score applies a hierarchical scoring system that weighs severity and type to assess clinical impacts; and MediHallDetector, trained via multitask learning on the benchmark, achieves improved detection performance over prior approaches.
What carries the argument
Med-HallMark benchmark together with the MediHall Score hierarchical severity-and-type metric that produces a single numeric assessment of hallucination risk.
If this is right
- Existing large vision-language models receive explicit baseline hallucination rates on medical tasks.
- MediHallDetector demonstrates higher detection accuracy than general-purpose methods when tested on the new benchmark.
- The scoring system distinguishes hallucination impacts at a finer level than aggregate accuracy or F1 metrics alone.
- Resources released allow other groups to train and compare models on the same medical hallucination tasks.
Where Pith is reading between the lines
- Adoption could shift medical AI evaluation from binary correctness checks toward graded risk profiles before clinical use.
- The multitask training pattern in MediHallDetector may transfer to hallucination detection in non-medical high-stakes vision-language settings.
- If the hierarchy proves stable, future work could extend the same structure to generate training signals that penalize high-severity errors more heavily.
Load-bearing premise
The hierarchical categories and severity levels used in MediHall Score match the actual clinical consequences that would arise from those errors in real medical settings.
What would settle it
A controlled deployment study in which model outputs scored by MediHall Score show no correlation with independent expert ratings of clinical harm on the same cases.
Figures
read the original abstract
Large Vision Language Models (LVLMs) are increasingly integral to healthcare applications, including medical visual question answering and imaging report generation. While these models inherit the robust capabilities of foundational Large Language Models (LLMs), they also inherit susceptibility to hallucinations-a significant concern in high-stakes medical contexts where the margin for error is minimal. However, currently, there are no dedicated methods or benchmarks for hallucination detection and evaluation in the medical field. To bridge this gap, we introduce Med-HallMark, the first benchmark specifically designed for hallucination detection and evaluation within the medical multimodal domain. This benchmark provides multi-tasking hallucination support, multifaceted hallucination data, and hierarchical hallucination categorization. Furthermore, we propose the MediHall Score, a new medical evaluative metric designed to assess LVLMs' hallucinations through a hierarchical scoring system that considers the severity and type of hallucination, thereby enabling a granular assessment of potential clinical impacts. We also present MediHallDetector, a novel Medical LVLM engineered for precise hallucination detection, which employs multitask training for hallucination detection. Through extensive experimental evaluations, we establish baselines for popular LVLMs using our benchmark. The findings indicate that MediHall Score provides a more nuanced understanding of hallucination impacts compared to traditional metrics and demonstrate the enhanced performance of MediHallDetector. We hope this work can significantly improve the reliability of LVLMs in medical applications. All resources of this work have been released at https://github.com/ydk122024/Med-HallMark.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper claims to introduce Med-HallMark as the first benchmark for hallucination detection and evaluation in medical LVLMs, supporting multi-tasking, multifaceted data, and hierarchical categorization. It proposes the MediHall Score as a hierarchical metric that accounts for hallucination type and severity to enable granular assessment of clinical impacts, along with MediHallDetector, a multitask-trained LVLM for detection. Experiments establish baselines for existing LVLMs and report that the new score is more nuanced than traditional metrics while the detector shows enhanced performance; all resources are released publicly.
Significance. If the benchmark construction and MediHall Score hierarchy can be externally validated, the work would fill a clear gap by providing domain-specific tools for assessing LVLMs in high-stakes medical imaging and VQA tasks. The public release of the benchmark, code, and data at the cited GitHub repository is a concrete strength that supports reproducibility.
major comments (3)
- [MediHall Score subsection] The definition and scoring rules for the MediHall Score (hierarchical severity levels and type categorization) are presented without any reported anchoring to clinical reality, such as inter-rater agreement statistics with practicing clinicians, correlation against downstream clinical error rates, or mapping to existing medical error taxonomies. This directly affects the central claim that the score enables a more nuanced understanding of clinical impacts than traditional metrics.
- [Benchmark construction section] The description of Med-HallMark benchmark construction provides no details on data sourcing, generation of the multifaceted hallucination examples, or any validation procedure (e.g., expert review or coverage analysis) for the hierarchical categories. Without this, it is impossible to evaluate whether the benchmark actually covers the error types that occur in medical practice, which is load-bearing for the claim that it is the first dedicated medical multimodal hallucination benchmark.
- [Experimental evaluations] The experimental section reports performance gains for MediHallDetector and advantages of the MediHall Score but does not include statistical significance tests, confidence intervals, or ablation controls on the multitask training. This weakens the ability to substantiate the baseline comparisons and the detector's claimed superiority.
minor comments (1)
- [MediHall Score subsection] Notation for the MediHall Score components could be introduced more formally with an equation or pseudocode to improve clarity when describing the hierarchical computation.
Simulated Author's Rebuttal
We thank the referee for the constructive feedback. We address each major comment below and indicate planned revisions to the manuscript.
read point-by-point responses
-
Referee: [MediHall Score subsection] The definition and scoring rules for the MediHall Score (hierarchical severity levels and type categorization) are presented without any reported anchoring to clinical reality, such as inter-rater agreement statistics with practicing clinicians, correlation against downstream clinical error rates, or mapping to existing medical error taxonomies. This directly affects the central claim that the score enables a more nuanced understanding of clinical impacts than traditional metrics.
Authors: We agree that empirical anchoring to clinical practice would strengthen the MediHall Score. The initial manuscript does not report inter-rater agreement or direct clinical correlations. In revision we will add a validation subsection with clinician ratings and inter-rater statistics to support the claim of nuanced clinical assessment. revision: yes
-
Referee: [Benchmark construction section] The description of Med-HallMark benchmark construction provides no details on data sourcing, generation of the multifaceted hallucination examples, or any validation procedure (e.g., expert review or coverage analysis) for the hierarchical categories. Without this, it is impossible to evaluate whether the benchmark actually covers the error types that occur in medical practice, which is load-bearing for the claim that it is the first dedicated medical multimodal hallucination benchmark.
Authors: We agree that the construction details are insufficient. We will expand the Benchmark construction section with explicit information on data sources, hallucination example generation, and any validation steps performed. revision: yes
-
Referee: [Experimental evaluations] The experimental section reports performance gains for MediHallDetector and advantages of the MediHall Score but does not include statistical significance tests, confidence intervals, or ablation controls on the multitask training. This weakens the ability to substantiate the baseline comparisons and the detector's claimed superiority.
Authors: We agree that statistical rigor is needed. We will add significance tests, confidence intervals, and multitask ablation controls to the experimental section in revision. revision: yes
Circularity Check
No circularity: benchmark and metric introduced by explicit construction
full rationale
The paper introduces Med-HallMark benchmark and MediHall Score via new hierarchical categorization and scoring rules defined within the work itself. No equations, fitted parameters called predictions, or load-bearing self-citations appear in the provided text. Claims rest on the artifacts' construction and experimental baselines rather than any reduction to prior inputs or self-referential definitions. This is a standard case of artifact introduction with independent content.
Axiom & Free-Parameter Ledger
Forward citations
Cited by 8 Pith papers
-
HalluCXR: Benchmarking and Mitigating Hallucinations in Medical Vision-Language Models for Chest Radiograph Interpretation
HalluCXR benchmark shows 61.9-82.3% hallucination rates across VLMs on MIMIC-CXR images, identifies patterns such as length-based risk and over-fabrication of common findings, and demonstrates ensemble mitigation that...
-
Evaluating the Search Agent in a Parallel World
Mind-ParaWorld creates parallel worlds with atomic facts to evaluate search agents on future scenarios, showing they synthesize evidence well but struggle with collection, coverage, sufficiency judgment, and stopping ...
-
Reducing Object Hallucination in LVLMs via Emphasizing Image-negative Tokens
Reweighting training emphasis toward image-negative tokens and filtering hallucinated data reduces object hallucination in LVLMs across three model variants.
-
VIHD: Visual Intervention-based Hallucination Detection for Medical Visual Question Answering
VIHD detects hallucinations in medical MLLMs by identifying visually dominant decoder layers via probing and applying visual token masking to calibrate semantic entropy as a detection signal.
-
MedVIGIL: Evaluating Trustworthy Medical VLMs Under Broken Visual Evidence
MedVIGIL introduces a clinician-supervised benchmark showing medical VLMs frequently give fluent answers on broken visual evidence, with top models 14 points below human radiologists on the composite score.
-
MedVIGIL: Evaluating Trustworthy Medical VLMs Under Broken Visual Evidence
MedVIGIL provides a 300-case evaluation suite with 2556 probes that measures silent failures in medical VLMs under broken evidence, showing the best model at 69.2 on the composite score versus a human radiologist at 83.3.
-
Mitigating Hallucinations in Large Vision-Language Models without Performance Degradation
MPD reduces hallucinations in LVLMs by 23.4% while retaining 97.4% of general capability through semantic disentanglement and selective parameter updates.
-
Mitigating Entangled Steering in Large Vision-Language Models for Hallucination Reduction
MESA reduces hallucinations in LVLMs via controlled selective latent intervention that preserves the original token distribution.
Reference graph
Works this paper leans on
- [1]
-
[2]
Hallucination of Multimodal Large Language Models: A Survey
Zechen Bai, Pichao Wang, Tianjun Xiao, Tong He, Zongbo Han, Zheng Zhang, and Mike Zheng Shou. Hallucination of multimodal large language models: A survey. arXiv preprint arXiv:2404.18930, 2024. 2, 4
work page internal anchor Pith review Pith/arXiv arXiv 2024
-
[3]
Miss: A generative pretraining and finetuning approach for med-vqa
Jiawei Chen, Dingkang Yang, Yue Jiang, et al. Miss: A generative pretraining and finetuning approach for med-vqa. arXiv preprint arXiv:2401.05163, 2024. 3, 4
-
[4]
Jiawei Chen, Dingkang Yang, Yue Jiang, Mingcheng Li, Jinjie Wei, Xiaolu Hou, and Lihua Zhang. Efficiency in focus: Layernorm as a catalyst for fine-tuning medical visual language pre-trained models. arXiv preprint arXiv:2404.16385, 2024. 3
-
[5]
Unified hallucination detection for multimodal large language models
Xiang Chen, Chenxi Wang, Yida Xue, Ningyu Zhang, Xiaoyan Yang, Qiang Li, Yue Shen, Jinjie Gu, and Huajun Chen. Unified hallucination detection for multimodal large language models. arXiv preprint arXiv:2402.03190, 2024. 2
-
[6]
InstructBLIP: Towards General-purpose Vision-Language Models with Instruction Tuning
W Dai, J Li, D Li, AMH Tiong, J Zhao, W Wang, B Li, P Fung, and S Hoi. Instructblip: Towards general-purpose vision-language models with instruction tuning. arxiv 2023. arXiv preprint arXiv:2305.06500. 1, 7
work page internal anchor Pith review Pith/arXiv arXiv 2023
-
[7]
Detecting and preventing hallucinations in large vision language models
Anisha Gunjal, Jihan Yin, and Erhan Bas. Detecting and preventing hallucinations in large vision language models. In Proceedings of the AAAI Conference on Artificial Intelligence , volume 38, pages 18135–18143, 2024. 2
work page 2024
-
[8]
Survey of hallucination in natural language generation
Ziwei Ji, Nayeon Lee, Rita Frieske, Tiezheng Yu, Dan Su, Yan Xu, Etsuko Ishii, Ye Jin Bang, Andrea Madotto, and Pascale Fung. Survey of hallucination in natural language generation. ACM Computing Surveys, 55(12):1–38, 2023. 2
work page 2023
-
[9]
Mimic-cxr, a de-identified publicly available database of chest radiographs with free-text reports
Alistair EW Johnson, Tom J Pollard, Seth J Berkowitz, Nathaniel R Greenbaum, Matthew P Lungren, Chih-ying Deng, Roger G Mark, and Steven Horng. Mimic-cxr, a de-identified publicly available database of chest radiographs with free-text reports. Scientific data, 6(1):317,
-
[10]
A dataset of clinically generated visual questions and answers about radiology images
Jason J Lau, Soumya Gayen, Asma Ben Abacha, and Dina Demner-Fushman. A dataset of clinically generated visual questions and answers about radiology images. Scientific data, 5(1):1–10, 2018. 2, 4
work page 2018
-
[11]
LLaVA-Med: Training a Large Language-and-Vision Assistant for Biomedicine in One Day
Chunyuan Li, Cliff Wong, Zhang, et al. Llava-med: Training a large language-and-vision assistant for biomedicine in one day. arXiv preprint arXiv:2306.00890, 2023. 2, 4, 7
work page internal anchor Pith review Pith/arXiv arXiv 2023
-
[12]
Junnan Li, Dongxu Li, Silvio Savarese, and Steven Hoi. Blip-2: Bootstrapping language- image pre-training with frozen image encoders and large language models. arXiv preprint arXiv:2301.12597, 2023. 1, 7
work page internal anchor Pith review Pith/arXiv arXiv 2023
-
[13]
Evaluating Object Hallucination in Large Vision-Language Models
Yifan Li, Yifan Du, Kun Zhou, Jinpeng Wang, Wayne Xin Zhao, and Ji-Rong Wen. Evaluating object hallucination in large vision-language models. arXiv preprint arXiv:2305.10355, 2023. 2, 3
work page internal anchor Pith review Pith/arXiv arXiv 2023
-
[14]
Slake: A semantically- labeled knowledge-enhanced dataset for medical visual question answering
Bo Liu, Li-Ming Zhan, Li Xu, Lin Ma, Yan Yang, and Xiao-Ming Wu. Slake: A semantically- labeled knowledge-enhanced dataset for medical visual question answering. In 2021 IEEE 18th International Symposium on Biomedical Imaging (ISBI), pages 1650–1654. IEEE, 2021. 2, 4
work page 2021
-
[15]
Mitigat- ing hallucination in large multi-modal models via robust instruction tuning
Fuxiao Liu, Kevin Lin, Linjie Li, Jianfeng Wang, Yaser Yacoob, and Lijuan Wang. Mitigat- ing hallucination in large multi-modal models via robust instruction tuning. In The Twelfth International Conference on Learning Representations, 2023. 2, 3
work page 2023
-
[16]
Llava-next: Improved reasoning, ocr, and world knowledge, 2024
Haotian Liu, Chunyuan Li, Yuheng Li, Bo Li, Yuanhan Zhang, Sheng Shen, and Yong Jae Lee. Llava-next: Improved reasoning, ocr, and world knowledge, 2024. 6
work page 2024
-
[17]
Haotian Liu, Chunyuan Li, Wu, et al. Visual instruction tuning.arXiv preprint arXiv:2304.08485,
work page internal anchor Pith review Pith/arXiv arXiv
-
[18]
Radiology objects in context (roco): a multimodal image dataset
Obioma Pelka, Sven Koitka, Rückert, et al. Radiology objects in context (roco): a multimodal image dataset. In LABELS 2018, MICCAI 2018, pages 180–189, 2018. 2
work page 2018
-
[19]
Object Hallucination in Image Captioning
Anna Rohrbach, Lisa Anne Hendricks, Kaylee Burns, Trevor Darrell, and Kate Saenko. Object hallucination in image captioning. arXiv preprint arXiv:1809.02156, 2018. 2, 3
work page internal anchor Pith review Pith/arXiv arXiv 2018
-
[20]
Xraygpt: Chest radiographs summarization using medical vision-language models
Omkar Thawkar, Abdelrahman Shaker, Sahal Shaji Mullappilly, Hisham Cholakkal, Rao Muhammad Anwer, Salman Khan, Jorma Laaksonen, and Fahad Shahbaz Khan. Xraygpt: Chest radiographs summarization using medical vision-language models. arXiv preprint arXiv:2306.07971, 2023. 2, 7
-
[21]
Evaluation and analysis of hallucination in large vision-language models
Junyang Wang, Yiyang Zhou, Guohai Xu, Pengcheng Shi, Chenlin Zhao, Haiyang Xu, Qinghao Ye, Ming Yan, Ji Zhang, Jihua Zhu, et al. Evaluation and analysis of hallucination in large vision-language models. arXiv preprint arXiv:2308.15126, 2023. 3
-
[22]
Xiaosong Wang, Yifan Peng, Le Lu, Zhiyong Lu, Mohammadhadi Bagheri, and Ronald M Summers. Chestx-ray8: Hospital-scale chest x-ray database and benchmarks on weakly- supervised classification and localization of common thorax diseases. In Proceedings of the IEEE conference on computer vision and pattern recognition, pages 2097–2106, 2017. 2, 4
work page 2097
-
[23]
Mitigating hallucinations in large vision-language models with instruction contrastive decoding
Xintong Wang, Jingheng Pan, Liang Ding, and Chris Biemann. Mitigating hallucinations in large vision-language models with instruction contrastive decoding. arXiv preprint arXiv:2403.18715,
-
[24]
Towards generalist foundation model for radiology, 2023
Chaoyi Wu, Xiaoman Zhang, Ya Zhang, Yanfeng Wang, and Weidi Xie. Towards generalist foundation model for radiology, 2023. 7
work page 2023
-
[25]
Detecting and mitigating hallucination in large vision language models via fine-grained ai feedback
Wenyi Xiao, Ziwei Huang, Leilei Gan, Wanggui He, Haoyuan Li, Zhelun Yu, Hao Jiang, Fei Wu, and Linchao Zhu. Detecting and mitigating hallucination in large vision language models via fine-grained ai feedback. arXiv preprint arXiv:2404.14233, 2024. 2
-
[26]
mPLUG-Owl2: Revolutionizing Multi-modal Large Language Model with Modality Collaboration
Qinghao Ye, Haiyang Xu, Jiabo Ye, Ming Yan, Haowei Liu, Qi Qian, Ji Zhang, Fei Huang, and Jingren Zhou. mplug-owl2: Revolutionizing multi-modal large language model with modality collaboration. arXiv preprint arXiv:2311.04257, 2023. 7
work page internal anchor Pith review Pith/arXiv arXiv 2023
-
[27]
Beyond Hallucinations: Enhancing LVLMs through Hallucination-Aware Direct Preference Optimization
Zhiyuan Zhao, Bin Wang, Linke Ouyang, Xiaoyi Dong, Jiaqi Wang, and Conghui He. Beyond hallucinations: Enhancing lvlms through hallucination-aware direct preference optimization. arXiv preprint arXiv:2311.16839, 2023. 2
work page internal anchor Pith review Pith/arXiv arXiv 2023
-
[28]
Analyzing and Mitigating Object Hallucination in Large Vision-Language Models
Yiyang Zhou, Chenhang Cui, Jaehong Yoon, Linjun Zhang, Zhun Deng, Chelsea Finn, Mohit Bansal, and Huaxiu Yao. Analyzing and mitigating object hallucination in large vision-language models. arXiv preprint arXiv:2310.00754, 2023. 2
work page internal anchor Pith review Pith/arXiv arXiv 2023
-
[29]
MiniGPT-4: Enhancing Vision-Language Understanding with Advanced Large Language Models
Deyao Zhu, Jun Chen, Xiaoqian Shen, Xiang Li, and Mohamed Elhoseiny. Minigpt-4: En- hancing vision-language understanding with advanced large language models. arXiv preprint arXiv:2304.10592, 2023. 7 12 Confidence-weakening Prefix1. As a developing AI with limited understanding of complex medical contexts, please provide your best interpretation to the qu...
work page internal anchor Pith review Pith/arXiv arXiv 2023
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.