FEU-Diff: A Diffusion Model With Fuzzy Evidence-Driven Dynamic Uncertainty Fusion for Medical Image Segmentation

Diffusion models, as a class of generative frameworks based on step-wise denoising, have recently attracted significant attention in the field of medical image segmentation. However, existing diffusion-based methods typically rely on static fusion strategies to integrate conditional priors with denoised features, making them difficult to adaptively balance their respective contributions at different denoising stages. Moreover, these methods often lack explicit modeling of pixel-level uncertainty in ambiguous regions, which may lead to the loss of structural details during the iterative denoising process, ultimately compromising the accuracy (Acc) and completeness of the final segmentation results. To this end, we propose FEU-Diff, a diffusion-based segmentation framework that integrates fuzzy evidence modeling and uncertainty fusion (UF) mechanisms. Specifically, a fuzzy semantic enhancement (FSE) module is designed to model pixel-level uncertainty through Gaussian membership functions and fuzzy logic rules, enhancing the model's ability to identify and represent ambiguous boundaries. An evidence dynamic fusion (EDF) module estimates feature confidence via a Dirichlet-based distribution and adaptively guides the fusion of conditional information and denoised features across different denoising stages. Furthermore, the UF module quantifies discrepancies among multisource predictions to compensate for structural detail loss during the iterative denoising process. Extensive experiments on four public datasets show that FEU-Diff consistently outperforms state-of-the-art (SOTA) methods, achieving an average gain of 1.42% in the Dice similarity coefficient (DSC), 1.47% in intersection over union (IoU), and a 2.26 mm reduction in the 95th percentile Hausdorff distance (HD95). In addition, our method generates uncertainty maps that enhance clinical interpretability.