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Advancing Generalizable Tumor Segmentation with Anomaly-Aware Open-Vocabulary Attention Maps and Frozen Foundation Diffusion Models
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Proposes DiffuGTS, which uses internal features of a frozen medical foundation diffusion model (MAISI) with anomaly-aware open-vocabulary attention maps and training-free latent inpainting plus pixel- and feature-level residual learning to segment unseen tumors zero-shot.
Problem
Zero-shot tumor segmentation across diverse anatomical regions and imaging modalities, where vision-language and SAM-based methods give limited segmentation quality and generalization.
Approach
Repurpose frozen MAISI VAE encoder features with text-prompt cross-attention to form anomaly-aware open-vocabulary attention maps, then refine masks by inpainting pseudo-healthy images with the frozen diffusion model and computing pixel-level and feature-level residuals.
Key results
- Leave-one-out zero-shot tumor segmentation: DiffuGTS reaches 59.80% DSC on kidney tumor (KiTS23) and 63.23% DSC on MSD liver tumor, outperforming ZePT and Malenia by at least 4.74% DSC.
- Unseen MRI modality setting: DiffuGTS achieves 50.31% DSC on in-house MRI liver tumor, surpassing the next best method by at least 21.28% DSC.
- Replacing AOVA maps with a Mask2Former backbone drops DSC on unseen MSD brain tumor from 47.51% to 36.57%.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| use DiffuGTS instead of the strongest listed baseline, Malenia | zero-shot tumor segmentation · MSD and KiTS23 tumor categories | DSC | Helped |
| use DiffuGTS instead of the strongest listed baseline, Malenia | zero-shot segmentation across unseen modalities · In-house MRI liver tumor, MSD-Brain, and BraTS23 | DSC | Helped |
| add frozen MAISI VAE features and adapters rather than train an nnUNet encoder from scratch (ablation) | DiffuGTS · MSD liver tumor | DSC: 60.40 -> 63.23 | Helped |
| add frozen MAISI VAE features and adapters rather than train an nnUNet encoder from scratch (ablation) | DiffuGTS · MSD brain tumor | DSC: 32.18 -> 47.51 | Helped |
| add feature adapters to frozen MAISI VAE features (ablation) | DiffuGTS · MSD liver tumor | DSC: 60.89 -> 63.23 | Helped |
| add feature adapters to frozen MAISI VAE features (ablation) | DiffuGTS · MSD brain tumor | DSC: 33.92 -> 47.51 | Helped |
| use adapters instead of fine-tuning the MAISI VAE (ablation) | DiffuGTS · MSD liver tumor | DSC: 61.18 -> 63.23 | Helped |
| use adapters instead of fine-tuning the MAISI VAE (ablation) | DiffuGTS · MSD brain tumor | DSC: 34.76 -> 47.51 | Helped |
| use AOVA maps instead of Mask2Former (ablation) | DiffuGTS with mask refinement · MSD liver tumor | DSC: 61.21 -> 63.23 | Helped |
| use AOVA maps instead of Mask2Former (ablation) | DiffuGTS with mask refinement · MSD brain tumor | DSC: 36.57 -> 47.51 | Helped |
| add diffusion-model mask refinement to AOVA maps (ablation) | DiffuGTS · MSD liver tumor | DSC: 59.94 -> 63.23 | Helped |
| add diffusion-model mask refinement to AOVA maps (ablation) | DiffuGTS · MSD brain tumor | DSC: 20.14 -> 47.51 | Helped |
Surprising findings
- The frozen-diffusion pipeline has about 12,876 GFLOPs versus roughly 3,887 GFLOPs for ZePT, which the authors flag as a substantial computational limitation.
- Fine-tuning the MAISI VAE encoder performs only slightly better than using it without an adapter, and both are far below the adapter variant.
Limitations
- High FLOPs from running the diffusion model for feature extraction and inpainting.
- Relies on MAISI as the frozen foundation model; generalization beyond its 127-structure conditioning is not tested.
- Evaluation covers only 7 tumor categories across four datasets with some private data.
Experimental setup
Datasets: MSD KiTS23 BraTS23 TotalSegmentator in-house MRI liver tumor dataset
Benchmarks: MSD KiTS23 BraTS23 MSD-Brain in-house MRI liver tumor dataset
Metrics: DSC NSD
Baselines: SAM 2 SaLIP H-SAM ZePT Malenia DDPM-MAD MVFA THOR
Builds on: MAISI CLIP RePaint Mask2Former
Closest papers by meaning
- ZePT: Zero-Shot Pan-Tumor Segmentation via Query-Disentangling and Self-Prompting (CVPR 2024 · similarity 0.89)
- DiffCut: Catalyzing Zero-Shot Semantic Segmentation with Diffusion Features and Recursive Normalized Cut (NeurIPS 2024 · similarity 0.85)
- Why Invariance is Not Enough for Biomedical Domain Generalization and How to Fix It (NeurIPS 2026 · similarity 0.85)
- Beyond ViT Tokens: Masked-Diffusion Pretrained Convolutional Pathology Foundation Model for Cell-Level Dense Prediction (NeurIPS 2026 · similarity 0.85)
- Adapting Visual-Language Models for Generalizable Anomaly Detection in Medical Images (CVPR 2024 · similarity 0.85)
- LangDAug: Langevin Data Augmentation for Multi-Source Domain Generalization in Medical Image Segmentation (ICML 2025 · similarity 0.84)
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