Xinwen Xu

Weiyi Wu, Xinwen Xu, Chongyang Gao et al.

Whole slide images, with their gigapixel-scale panoramas of tissue samples, are pivotal for precise disease diagnosis. However, their analysis is hindered by immense data size and scarce annotations. Existing MIL methods face challenges due to the fundamental imbalance where a single bag-level label must guide the learning of numerous patch-level features. This sparse supervision makes it difficult to reliably identify discriminative patches during training, leading to unstable optimization and suboptimal solutions. We propose a spatially regularized MIL framework that leverages inherent spatial relationships among patch features as label-independent regularization signals. Our approach learns a shared representation space by jointly optimizing feature-induced spatial reconstruction and label-guided classification objectives, enforcing consistency between intrinsic structural patterns and supervisory signals. Experimental results on multiple public datasets demonstrate significant improvements over state-of-the-art methods, offering a promising direction.

Weiyi Wu, Xinwen Xu, Chongyang Gao et al.

Large Language Models (LLMs) have great potential in the field of health care, yet they face great challenges in adapting to rapidly evolving medical knowledge. This can lead to outdated or contradictory treatment suggestions. This study investigated how LLMs respond to evolving clinical guidelines, focusing on concept drift and internal inconsistencies. We developed the DriftMedQA benchmark to simulate guideline evolution and assessed the temporal reliability of various LLMs. Our evaluation of seven state-of-the-art models across 4,290 scenarios demonstrated difficulties in rejecting outdated recommendations and frequently endorsing conflicting guidance. Additionally, we explored two mitigation strategies: Retrieval-Augmented Generation and preference fine-tuning via Direct Preference Optimization. While each method improved model performance, their combination led to the most consistent and reliable results. These findings underscore the need to improve LLM robustness to temporal shifts to ensure more dependable applications in clinical practice. The dataset is available at https://huggingface.co/datasets/RDBH/DriftMed.

Junxiang Wang, Xinwen Xu, Tiancheng Wu et al.

Developing autonomous physical human-robot interaction (pHRI) systems is limited by the scarcity of large-scale training data to learn robust robot behaviors for real-world applications. In this paper, we introduce a zero-shot "text2sim2real" generative simulation framework that automatically synthesizes diverse pHRI scenarios from high-level natural-language prompts. Leveraging Large Language Models (LLMs) and Vision-Language Models (VLMs), our pipeline procedurally generates soft-body human models, scene layouts, and robot motion trajectories for assistive tasks. We utilize this framework to autonomously collect large-scale synthetic demonstration datasets and then train vision-based imitation learning policies operating on segmented point clouds. We evaluate our approach through a user study on two physically assistive tasks: scratching and bathing. Our learned policies successfully achieve zero-shot sim-to-real transfer, attaining success rates exceeding 80% and demonstrating resilience to unscripted human motion. Overall, we introduce the first generative simulation pipeline for pHRI applications, automating simulation environment synthesis, data collection, and policy learning. Additional information may be found on our project website: https://rchi-lab.github.io/gen_phri/

Xingjian Diao, Weiyi Wu, Keyi Kong et al.

Visual Question Answering (VQA) is increasingly used in diverse applications ranging from general visual reasoning to safety-critical domains such as medical imaging and autonomous systems, where models must provide not only accurate answers but also explanations that humans can easily understand and verify. Prototype-based modeling has shown promise for interpretability by grounding predictions in semantically meaningful regions for purely visual reasoning tasks, yet remains underexplored in the context of VQA. We present ProtoVQA, a unified prototypical framework that (i) learns question-aware prototypes that serve as reasoning anchors, connecting answers to discriminative image regions, (ii) applies spatially constrained matching to ensure that the selected evidence is coherent and semantically relevant, and (iii) supports both answering and grounding tasks through a shared prototype backbone. To assess explanation quality, we propose the Visual-Linguistic Alignment Score (VLAS), which measures how well the model's attended regions align with ground-truth evidence. Experiments on Visual7W show that ProtoVQA yields faithful, fine-grained explanations while maintaining competitive accuracy, advancing the development of transparent and trustworthy VQA systems.

Weiyi Wu, Xingjian Diao, Chongyang Gao et al.

Whole slide images (WSIs) present fundamental computational challenges due to their gigapixel-scale resolutions and sparse, irregularly distributed informative regions. Conventional patch-based methods inevitably distort spatial relationships or treat patches as independent samples, while traditional attention mechanisms, designed for dense, uniformly distributed data, are computationally impractical for WSIs. To address these limitations, we propose a novel sparse-native computational framework that preserves exact spatial relationships, unlocking advanced modeling techniques and bridging a long-standing gap between WSI analysis and general vision. Based on this framework, we develop Sparse Pyramid Attention Networks (SPAN), incorporating a hierarchical sparse pyramid attention architecture with shifted windows that efficiently directs computational resources to informative regions. SPAN comprises two key modules: Spatial-Adaptive Feature Condensation, which progressively builds multi-scale representations from a single-scale input through sparse downsampling, and Context-Aware Feature Refinement, which captures long-range dependencies via shifted windows and global tokens. Evaluations on multiple public datasets demonstrate SPAN's superior performance over state-of-the-art methods, validating both our framework's effectiveness and SPAN's specific advantages in capturing contextual and hierachical representations that existing methods fundamentally cannot model. Our work establishes a new paradigm for WSI analysis that overcomes long-standing computational barriers. The code will be made publicly available upon publication.