• Propose MorphoNet framework to capture morphological patterns and long-range tissue structures in WSIs. • Develop a Morphological Sub-Region Grouping mechanism to model WSIs as spatially coherent sub-regions. • Introduce a spatial-aware clustering approach and a sub-region aggregation strategy to derive sub-region embeddings. • Achieve superior performance across 10 public benchmarks, outperforming state-of-the-art methods in tumor subtyping and survival prediction. Representation learning of Whole slide image (WSI) is fundamental to computational pathology, enabling tasks such as tumor subtyping, survival prediction, and cancer grading. Existing methods typically tile WSIs into thousands of small patches and aggregate patch features into slide-level embeddings, but this patch-centric paradigm suffers from redundancy and suboptimal spatial modeling. Built upon these patch-level embeddings, Multiple Instance Learning (MIL) methods overfit to scattered discriminative patches, graph-based models mainly capture local neighborhoods, and prototype-based approaches often ignore spatial coherence and under-represent rare tissue patterns. To address these challenges, we propose MorphoNet, a Morph ological structure learning Net work that captures long-range spatial tissue relationships while extracting informative morphological patterns. The key idea of MorphoNet is Morphological Sub-Region Grouping (MSRG), which clusters spatially adjacent patches with similar appearance into compact sub-region embeddings, reducing redundancy and forming semantically coherent morphological units. Sub-region graph is then constructed and processed by a lightweight Graph Neural Network (GNN) to model contextual dependencies and derive slide-level representations. Importantly, MSRG is a plug-and-play module that can be integrated into MIL, graph-based, and prototype-based pipelines, consistently improving their performance. Experiments on ten public benchmarks demonstrate that MorphoNet achieves superior performance on tumor subtyping and survival prediction. Our code is available at https://github.com/fuying-wang/MorphoNet .

Electrocardiograms (ECGs) play a vital role in monitoring cardiac health and diagnosing heart diseases. However, traditional deep learning approaches for ECG analysis rely heavily on large-scale manual annotations, which are both time-consuming and resource-intensive to obtain. To overcome this limitation, self-supervised learning (SSL) has emerged as a promising alternative, enabling the extraction of robust ECG representations that can be efficiently transferred to various downstream tasks. While previous studies have explored SSL for ECG pretraining and multi-modal ECG-language alignment, they often fail to capture the multi-scale nature of ECG signals. As a result, these methods struggle to learn generalized representations due to their inability to model the hierarchical structure of ECG data. To address this gap, we introduce MELP, a novel Multi-scale ECG-Language Pretraining (MELP) model that fully leverages hierarchical supervision from ECG-text pairs. MELP first pretrains a cardiology-specific language model to enhance its understanding of clinical text. It then applies three levels of cross-modal supervision—at the token, beat, and rhythm levels—to align ECG signals with textual reports, capturing structured information across different time scales. We evaluate MELP on three public ECG datasets across multiple tasks, including zero-shot ECG classification, linear probing, and transfer learning. Experimental results demonstrate that MELP outperforms existing SSL methods, underscoring its effectiveness and adaptability across diverse clinical applications. Our code is available at https://github.com/HKU-MedAI/MELP.

Various data modalities are common in real-world applications. (e.g., EHR, medical images and clinical notes in healthcare). Thus, it is essential to develop multimodal learning methods to aggregate information from multiple modalities. The main challenge is appropriately aligning and fusing the representations of different modalities into a joint distribution. Existing methods mainly rely on concatenation or the Kronecker product, oversimplifying interactions structure between modalities and indicating a need to model more complex interactions. Additionally, the joint distribution of latent representations with higher-order interactions is underexplored. Copula is a powerful statistical structure in modelling the interactions between variables, as it bridges the joint distribution and marginal distributions of multiple variables. In this paper, we propose a novel copula modelling-driven multimodal learning framework, which focuses on learning the joint distribution of various modalities to capture the complex interaction among them. The key idea is interpreting the copula model as a tool to align the marginal distributions of the modalities efficiently. By assuming a Gaussian mixture distribution for each modality and a copula model on the joint distribution, our model can also generate accurate representations for missing modalities. Extensive experiments on public MIMIC datasets demonstrate the superior performance of our model over other competitors. The code is anonymously available at https://github.com/HKU-MedAI/CMCM.

Learning contextual features such as interactions among various biological entities is vital for whole slide images (WSI)-based cancer diagnosis and prognosis. Graph-based methods have surpassed traditional multi-instance learning in WSI analysis by robustly integrating local pathological and contextual interaction features. However, the high resolution of WSIs often leads to large, noisy graphs. This can result in shortcut learning and overfitting due to the disproportionate graph size relative to WSI datasets. To overcome these issues, we propose a novel Task-Aware Disentanglement Graph approach (TAD-Graph) for more efficient WSI analysis. TAD-Graph operates on WSI graph representations, effectively identifying and disentangling informative subgraphs to enhance contextual feature extraction. Specifically, we inject stochasticity into the edge connections of the WSI graph and separate the WSI graph into task-relevant and task-irrelevant subgraphs. The disentanglement procedure is optimized using a graph information bottleneck-based objective, with added constraints on the task-irrelevant subgraph to reduce spurious correlations from task-relevant subgraphs to labels. TAD-Graph outperforms existing methods in three WSI analysis tasks across six benchmark datasets. Furthermore, our analysis using pathological concept-based metrics demonstrates TAD-Graph's ability to not only improve predictive accuracy but also provide interpretive insights and aid in potential biomarker identification. Our code is publicly available at https://github.com/fuying-wang/TAD-Graph.

Foundation models have significantly revolutionized the field of chest X-ray diagnosis with their ability to transfer across various diseases and tasks. However, previous works have predominantly utilized self-supervised learning from medical image-text pairs, which falls short in dense medical prediction tasks due to their sole reliance on such coarse pair supervision, thereby limiting their applicability to detailed diagnostics. In this paper, we introduce a Dense Chest X-ray Foundation Model (DCXFM), which utilizes mixed supervision types (i.e., text, label, and segmentation masks) to significantly enhance the scalability of foundation models across various medical tasks. Our model involves two training stages: we first employ a novel self-distilled multimodal pretraining paradigm to exploit text and label supervision, along with local-to-global self-distillation and soft cross-modal contrastive alignment strategies to enhance localization capabilities. Subsequently, we introduce an efficient cost aggregation module, comprising spatial and class aggregation mechanisms, to further advance dense prediction tasks with densely annotated datasets. Comprehensive evaluations on three tasks (phrase grounding, zero-shot semantic segmentation, and zero-shot classification) demonstrate DCXFM's superior performance over other state-of-the-art medical image-text pretraining models. Remarkably, DCXFM exhibits powerful zero-shot capabilities across various datasets in phrase grounding and zero-shot semantic segmentation, underscoring its superior generalization in dense prediction tasks.

Learning medical visual representations directly from paired radiology reports has become an emerging topic in representation learning. However, existing medical image-text joint learning methods are limited by instance or local supervision analysis, ignoring disease-level semantic correspondences. In this paper, we present a novel Multi-Granularity Cross-modal Alignment (MGCA) framework for generalized medical visual representation learning by harnessing the naturally exhibited semantic correspondences between medical image and radiology reports at three different levels, i.e., pathological region-level, instance-level, and disease-level. Specifically, we first incorporate the instance-wise alignment module by maximizing the agreement between image-report pairs. Further, for token-wise alignment, we introduce a bidirectional cross-attention strategy to explicitly learn the matching between fine-grained visual tokens and text tokens, followed by contrastive learning to align them. More important, to leverage the high-level inter-subject relationship semantic (e.g., disease) correspondences, we design a novel cross-modal disease-level alignment paradigm to enforce the cross-modal cluster assignment consistency. Extensive experimental results on seven downstream medical image datasets covering image classification, object detection, and semantic segmentation tasks demonstrate the stable and superior performance of our framework.

Human beings and animals are capable of recognizing places from a previous journey when viewing them under different environmental conditions (e.g., illuminations and weathers). This paper seeks to provide robots with a human-like place recognition ability using a new point cloud feature learning method. This is a challenging problem due to the difficulty of extracting invariant local descriptors from the same place under various orientation differences and dynamic obstacles. In this paper, we propose a novel lightweight 3D place recognition method, SeqSphereVLAD, which is capable of recognizing places from a previous trajectory regardless of the viewpoint and the temporary observation differences. The major contributions of our method lie in two modules: (1) the spherical convolution feature extraction module, which produces orientation-invariant local place descriptors, and (2) the coarse-to-fine sequence matching module, which ensures both accurate loop-closure detection and real-time performance. Despite the apparent simplicity, our proposed approach outperform the state-of-the-arts for place recognition under datasets that combine orientation and context differences. Compared with the arts, our method can achieve above 95% average recall for the best match with only 18% inference time of PointNet-based place recognition methods.