Existing whole heart segmentation algorithms usually combine 3D Convolutional Neural Networks (3D CNNs) with Transformers, for the purpose of capturing local and global features. However, traditional CNNs with a fixed size of receptive field cannot capture long-range contextual information. Transformers have been widely used to establish dependencies on global information, despite this, they greatly increase the computational complexity. To mitigate these challenges, we propose a hybrid paradigm, called Transfer Attention-Guided MultiReceptive Field Network (TAMRNet), to boost the representation quality for multi-modality cardiac image segmentation. In TAMRNet, the novel adaptive-scale depthwise convolution module adeptly preserves the inherent inductive biases of convolution while concurrently amplifying the network's ability to establish dependencies on long-range contextual information. Besides, a novel attention mechanism called Transfer Attention is developed to establish dependencies on global information. Transfer Attention avoids the direct similarity calculation of$Q$and$K$by introducing the Transfer tokens, and thus dramatically decreases the computational cost. The proposed TAMRNet is tested on the MM-WHS 2017 challenge dataset, achieving the average Dice scores of 93.7 % and 82.2 % on the CT and MRI datasets respectively. Extensive experimental results prove that our proposed method achieves superior performances in comparison with state-of-the-art methods.

Given the significant advancements in thoracic disease diagnosis due to deep learning, there is a reliance on the availability of numerous annotated samples, which, however, can hardly be guaranteed due to the resource-intensive nature of medical image annotation. Active learning has been introduced to mitigate annotation costs by selecting a subset of uncertain samples for annotation and training. Existing active learning methods encounter two primary challenges: 1) overlooking the impact of samples on the dynamics of model training during data selection, and 2) suffering from high costs of data evaluation and selection. To tackle both issues, we propose a novel metric called Temporal Difference of Gradient Flow (TDGF) for data selection in active learning. Each round of active learning involves three steps: model training, data selection, and data annotation. First, we train a target model, a proxy model, and a historical proxy model on the labeled set. Second, the TDGF scores of unlabeled samples are evaluated based on the surrogate gradient flow, i.e., the TDGF w.r.t the final fully-connected layer between the proxy and historical proxy models, and top-K samples with the highest TDGF scores are selected. Third, the selected samples are annotated, and the labeled pool and unlabeled pool are updated. Comparative experiments have been conducted on two public chest radiograph datasets, i.e., ChestX-ray14 and CheXpert. Our results suggest that the proposed TDGF metric is prone to selecting hard and uncertain samples, and the use of proxy models and surrogate gradient flow substantially reduces the complexity of TDGF calculation. More importantly, the results also indicate that our TDGF-based method outperforms classical and state-of-the-art active learning methods in thoracic disease diagnosis.

Cardiovascular disease is a leading global cause of death, requiring accurate heart segmentation for diagnosis and surgical planning. Deep learning methods have been demonstrated to achieve superior performances in cardiac structures segmentation. However, there are still limitations in 3D whole heart segmentation, such as inadequate spatial context modeling, difficulty in capturing long-distance dependencies, high computational complexity, and limited representation of local high-level semantic information. To tackle the above problems, we propose a lightweight Pyramid Pooling Transformer-CNN (P2TC) network for accurate 3D whole heart segmentation. The proposed architecture comprises a dual encoder-decoder structure with a 3D pyramid pooling Transformer for multi-scale information fusion and a lightweight large-kernel Convolutional Neural Network (CNN) for local feature extraction. The decoder has two branches for precise segmentation and contextual residual handling. The first branch is used to generate segmentation masks for pixel-level classification based on the features extracted by the encoder to achieve accurate segmentation of cardiac structures. The second branch highlights contextual residuals across slices, enabling the network to better handle variations and boundaries. Extensive experimental results on the Multi-Modality Whole Heart Segmentation (MM-WHS) 2017 challenge dataset demonstrate that P2TC outperforms the most advanced methods, achieving the Dice scores of 92.6% and 88.1% in Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) modalities respectively, which surpasses the baseline model by 1.5% and 1.7%, and achieves state-of-the-art segmentation results.

Federated learning facilitates the collaborative learning of a global model across multiple distributed medical in-stitutions without centralizing data. Nevertheless, the ex-pensive cost of annotation on local clients remains an ob-stacle to effectively utilizing local data. To mitigate this issue, federated active learning methods suggest leveraging local and global model predictions to select a relatively small amount of informative local data for annotation. However, existing methods mainly focus on all local data sampled from the same domain, making them un-reliable in realistic medical scenarios with domain shifts among different clients. In this paper, we make the first at-tempt to assess the informativeness of local data derived from diverse domains and propose a novel methodology termed Federated Evidential Active Learning (FEAL) to calibrate the data evaluation under domain shift. Specif-ically, we introduce a Dirichlet prior distribution in both local and global models to treat the prediction as a distribution over the probability simplex and capture both aleatoric and epistemic uncertainties by using the Dirichlet-based evidential model. Then we employ the epistemic uncer-tainty to calibrate the aleatoric uncertainty. Afterward, we design a diversity relaxation strategy to reduce data re-dundancy and maintain data diversity. Extensive experi-ments and analysis on five real multi-center medical image datasets demonstrate the superiority of FEAL over the state-of-the-art active learning methods in federated sce-narios with domain shifts. The code will be available at https://github.com/JiayiChen815/FEAL.

Accurate myocardial segmentation is crucial in the diagnosis and treatment of myocardial infarction (MI), especially in Late Gadolinium Enhancement (LGE) cardiac magnetic resonance (CMR) images, where the infarcted myocardium exhibits a greater brightness. However, segmentation annotations for LGE images are usually not available. Although knowledge gained from CMR images of other modalities with ample annotations, such as balanced-Steady State Free Precession (bSSFP), can be transferred to the LGE images, the difference in image distribution between the two modalities (i.e., domain shift) usually results in a significant degradation in model performance. To alleviate this, an end-to-end Variational autoencoder based feature Alignment Module Combining Explicit and Implicit features (VAMCEI) is proposed. We first re-derive the Kullback-Leibler (KL) divergence between the posterior distributions of the two domains as a measure of the global distribution distance. Second, we calculate the prototype contrastive loss between the two domains, bringing closer the prototypes of the same category across domains and pushing away the prototypes of different categories within or across domains. Finally, a domain discriminator is added to the output space, which indirectly aligns the feature distribution and forces the extracted features to be more favorable for segmentation. In addition, by combining CycleGAN and VAMCEI, we propose a more refined multi-stage unsupervised domain adaptation (UDA) framework for myocardial structure segmentation. We conduct extensive experiments on the MSCMRSeg 2019, MyoPS 2020 and MM-WHS 2017 datasets. The experimental results demonstrate that our framework achieves superior performances than state-of-the-art methods.

Chest radiography is the most common radiology examination for thoracic disease diagnosis, such as pneumonia. A tremendous number of chest X-rays prompt data-driven deep learning models in constructing computer-aided diagnosis systems for thoracic diseases. However, in realistic radiology practice, a deep learning-based model often suffers from performance degradation when trained on data with noisy labels possibly caused by different types of annotation biases. To this end, we present a novel stochastic neural ensemble learning (SNEL) framework for robust thoracic disease diagnosis using chest X-rays. The core idea of our method is to learn from noisy labels by constructing model ensembles and designing noise-robust loss functions. Specifically, we propose a fast neural ensemble method that collects parameters simultaneously across model instances and along optimization trajectories. Moreover, we propose a loss function that both optimizes a robust measure and characterizes a diversity measure of ensembles. We evaluated our proposed SNEL method on three publicly available hospital-scale chest X-ray datasets. The experimental results indicate that our method outperforms competing methods and demonstrate the effectiveness and robustness of our method in learning from noisy labels. Our code is available at https://github.com/hywang01/SNEL.

Detailed information of substructures of the whole heart is usually vital in the diagnosis of cardiovascular diseases and in 3D modeling of the heart. Deep convolutional neural networks have been demonstrated to achieve state-of-the-art performance in 3D cardiac structures segmentation. However, when dealing with high-resolution 3D data, current methods employing tiling strategies usually degrade segmentation performances due to GPU memory constraints. This work develops a two-stage multi-modality whole heart segmentation strategy, which adopts an improved Combination of Faster R-CNN and 3D U-Net (CFUN+). More specifically, the bounding box of the heart is first detected by Faster R-CNN, and then the original Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) images of the heart aligned with the bounding box are input into 3D U-Net for segmentation. The proposed CFUN+ method redefines the bounding box loss function by replacing the previous Intersection over Union (IoU) loss with Complete Intersection over Union (CIoU) loss. Meanwhile, the integration of the edge loss makes the segmentation results more accurate, and also improves the convergence speed. The proposed method achieves an average Dice score of 91.1% on the Multi-Modality Whole Heart Segmentation (MM-WHS) 2017 challenge CT dataset, which is 5.2% higher than the baseline CFUN model, and achieves state-of-the-art segmentation results. In addition, the segmentation speed of a single heart has been dramatically improved from a few minutes to less than 6 seconds.