Task transfer learning is a popular technique in image processing applications that uses pre-trained models to reduce the supervision cost of related tasks. An important question is to determine task transferability, i.e. given a common input domain, estimating to what extent representations learned from a source task can help in learning a target task. Typically, transferability is either measured experimentally or inferred through task relatedness, which is often defined without a clear operational meaning. In this paper, we present a novel metric, H-score, an easily-computable evaluation function that estimates the performance of transferred representations from one task to another in classification problems using statistical and information theoretic principles. Experiments on real image data show that our metric is not only consistent with the empirical transferability measurement, but also useful to practitioners in applications such as source model selection and task transfer curriculum learning.

The number of international benchmarking competitions is steadily increasing in various fields of machine learning (ML) research and practice. So far, however, little is known about the common practice as well as bottlenecks faced by the community in tackling the research questions posed. To shed light on the status quo of algorithm development in the specific field of biomedical imaging analysis, we designed an international survey that was issued to all participants of challenges conducted in conjunction with the IEEE ISBI 2021 and MICCAI 2021 conferences (80 competitions in total). The survey covered participants' expertise and working environments, their chosen strategies, as well as algorithm characteristics. A median of 72% challenge participants took part in the survey. According to our results, knowledge exchange was the primary incentive (70%) for participation, while the reception of prize money played only a minor role (16%). While a median of 80 working hours was spent on method development, a large portion of participants stated that they did not have enough time for method development (32%). 25% perceived the infrastructure to be a bottleneck. Overall, 94% of all solutions were deep learning-based. Of these, 84% were based on standard architectures. 43% of the respondents reported that the data samples (e.g., images) were too large to be processed at once. This was most commonly addressed by patch-based training (69%), downsampling (37%), and solving 3D analysis tasks as a series of 2D tasks. K-fold cross-validation on the training set was performed by only 37% of the participants and only 50% of the participants performed ensembling based on multiple identical models (61%) or heterogeneous models (39%). 48% of the respondents applied postprocessing steps.

Deep neural networks have strong capabilities of memorizing the underlying training data, which can be a serious privacy concern. An effective solution to this problem is to train models with differential privacy, which provides rigorous privacy guarantees by injecting random noise to the gradients. This paper focuses on the scenario where sensitive data are distributed among multiple participants, who jointly train a model through federated learning (FL), using both secure multiparty computation (MPC) to ensure the confidentiality of each gradient update, and differential privacy to avoid data leakage in the resulting model. A major challenge in this setting is that common mechanisms for enforcing DP in deep learning, which inject real-valued noise, are fundamentally incompatible with MPC, which exchanges finite-field integers among the participants. Consequently, most existing DP mechanisms require rather high noise levels, leading to poor model utility. Motivated by this, we propose Skellam mixture mechanism (SMM), an approach to enforce DP on models built via FL. Compared to existing methods, SMM eliminates the assumption that the input gradients must be integer-valued, and, thus, reduces the amount of noise injected to preserve DP. Further, SMM allows tight privacy accounting due to the nice composition and sub-sampling properties of the Skellam distribution, which are key to accurate deep learning with DP. The theoretical analysis of SMM is highly non-trivial, especially considering (i) the complicated math of differentially private deep learning in general and (ii) the fact that the mixture of two Skellam distributions is rather complex, and to our knowledge, has not been studied in the DP literature. Extensive experiments on various practical settings demonstrate that SMM consistently and significantly outperforms existing solutions in terms of the utility of the resulting model.

Objective: Thigh muscle group segmentation is important for assessment of muscle anatomy, metabolic disease and aging. Many efforts have been put into quantifying muscle tissues with magnetic resonance (MR) imaging including manual annotation of individual muscles. However, leveraging publicly available annotations in MR images to achieve muscle group segmentation on single slice computed tomography (CT) thigh images is challenging. Method: We propose an unsupervised domain adaptation pipeline with self-training to transfer labels from 3D MR to single CT slice. First, we transform the image appearance from MR to CT with CycleGAN and feed the synthesized CT images to a segmenter simultaneously. Single CT slices are divided into hard and easy cohorts based on the entropy of pseudo labels inferenced by the segmenter. After refining easy cohort pseudo labels based on anatomical assumption, self-training with easy and hard splits is applied to fine tune the segmenter. Results: On 152 withheld single CT thigh images, the proposed pipeline achieved a mean Dice of 0.888(0.041) across all muscle groups including sartorius, hamstrings, quadriceps femoris and gracilis. muscles Conclusion: To our best knowledge, this is the first pipeline to achieve thigh imaging domain adaptation from MR to CT. The proposed pipeline is effective and robust in extracting muscle groups on 2D single slice CT thigh images.The container is available for public use at https://github.com/MASILab/DA_CT_muscle_seg

2D低剂量单板腹部计算机断层扫描（CT）切片可直接测量身体成分，这对于对衰老的健康关系进行定量表征至关重要。然而，由于不同年内获得的纵向切片之间的位置方差，使用2D腹部切片对人体成分变化的纵向分析具有挑战性。为了减少位置差异，我们将条件生成模型扩展到我们的C-斜肌，该模型在腹部区域进行任意轴向切片作为条件，并通过估计潜在空间的结构变化来生成定义的椎骨水平切片。对来自内部数据集的1170名受试者的实验和BTCV Miccai挑战赛的50名受试者的实验表明，我们的模型可以从现实主义和相似性方面产生高质量的图像。来自巴尔的摩纵向研究（BLSA）数据集的20名受试者的外部实验，其中包含纵向单腹部切片验证了我们的方法可以在肌肉和内脏脂肪面积方面与切片的位置方差进行协调。我们的方法提供了一个有希望的方向，将切片从不同的椎骨水平映射到目标切片，以减少单个切片纵向分析的位置差异。源代码可在以下网址获得：https：//github.com/masilab/c-slicegen。

Transformer-based models, capable of learning better global dependencies, have recently demonstrated exceptional representation learning capabilities in computer vision and medical image analysis. Transformer reformats the image into separate patches and realize global communication via the self-attention mechanism. However, positional information between patches is hard to preserve in such 1D sequences, and loss of it can lead to sub-optimal performance when dealing with large amounts of heterogeneous tissues of various sizes in 3D medical image segmentation. Additionally, current methods are not robust and efficient for heavy-duty medical segmentation tasks such as predicting a large number of tissue classes or modeling globally inter-connected tissues structures. Inspired by the nested hierarchical structures in vision transformer, we proposed a novel 3D medical image segmentation method (UNesT), employing a simplified and faster-converging transformer encoder design that achieves local communication among spatially adjacent patch sequences by aggregating them hierarchically. We extensively validate our method on multiple challenging datasets, consisting anatomies of 133 structures in brain, 14 organs in abdomen, 4 hierarchical components in kidney, and inter-connected kidney tumors). We show that UNesT consistently achieves state-of-the-art performance and evaluate its generalizability and data efficiency. Particularly, the model achieves whole brain segmentation task complete ROI with 133 tissue classes in single network, outperforms prior state-of-the-art method SLANT27 ensembled with 27 network tiles, our model performance increases the mean DSC score of the publicly available Colin and CANDI dataset from 0.7264 to 0.7444 and from 0.6968 to 0.7025, respectively.

从心脏病学到神经病学的疾病中，代谢健康越来越多地成为危险因素，身体成分的效率评估对于定量表征这些关系至关重要。 2D低剂量单切层扫描术（CT）提供了高分辨率，定量组织图，尽管视野有限。尽管在量化图像上下文时已经提出了许多潜在的分析，但尚无对低剂量单切片CT纵向变异性进行自动分割的全面研究。我们使用受监督的基于深度学习的细分和无监督的聚类方法研究了1469个巴尔的摩纵向研究（BLSA）腹部数据集的1469名纵向研究（BLSA）腹部数据集的1816片。在前两次扫描中有两年差距的1469名受试者中有300名被选出，以评估纵向变异性，其中包括类内相关系数（ICC）和变异系数（CV），以组织/器官的大小和平均强度为单位。我们表明，我们的分割方法在纵向环境中是稳定的，骰子范围为13个目标腹部组织结构的0.821至0.962。我们观察到ICC <0.5的大多数器官的较高变异性，肌肉，腹壁，脂肪和体膜的变化较低，平均ICC> 0.8。我们发现器官的变异性与2D切片的横截面位置高度相关。我们的努力铺平了定量探索和质量控制，以减少纵向分析中的不确定性。

在深度感知的固有歧义的范围内，现代相机的3D对象检测方法属于性能瓶颈。从直觉上讲，利用时间多视角立体声（MVS）技术是解决这种歧义的自然知识。但是，在适用于3D对象检测场景时，MV的传统尝试在两个方面存在缺陷：1）所有观点之间的亲和力测量遭受昂贵的计算成本； 2）很难处理经常移动物体的室外场景。为此，我们引入了一种有效的时间立体声方法，以动态选择匹配候选者的尺度，从而显着减少计算开销。更进一步，我们设计了一种迭代算法，以更新更有价值的候选人，使其适应移动候选人。我们将我们提出的方法实例化，以进行多视图3D检测器，即Bevstereo。 Bevstereo在Nuscenes数据集的仅相机轨道上实现了新的最先进的性能（即52.5％地图和61.0％NDS）。同时，广泛的实验反映了我们的方法比当代MVS方法更好地处理复杂的室外场景。代码已在https://github.com/megvii astection/bevstereo上发布。

实时音乐伴奏的生成在音乐行业（例如音乐教育和现场表演）中具有广泛的应用。但是，自动实时音乐伴奏的产生仍在研究中，并且经常在逻辑延迟和暴露偏见之间取决于权衡。在本文中，我们提出了Song Driver，这是一种无逻辑延迟或暴露偏见的实时音乐伴奏系统。具体而言，Songdriver将一个伴奏的生成任务分为两个阶段：1）安排阶段，其中变压器模型首先安排了和弦，以实时进行输入旋律，并在下一阶段加速了和弦，而不是播放它们。 2）预测阶段，其中CRF模型基于先前缓存的和弦生成了即将到来的旋律的可播放的多轨伴奏。通过这种两相策略，歌手直接生成即将到来的旋律的伴奏，从而达到了零逻辑延迟。此外，在预测时间步的和弦时，歌手是指第一阶段的缓存和弦，而不是其先前的预测，这避免了暴露偏见问题。由于输入长度通常在实时条件下受到限制，因此另一个潜在的问题是长期顺序信息的丢失。为了弥补这一缺点，我们在当前时间步骤作为全球信息之前从长期音乐作品中提取了四个音乐功能。在实验中，我们在一些开源数据集上训练歌手，以及由中国风格的现代流行音乐得分构建的原始\```````'''aisong数据集。结果表明，歌手在客观和主观指标上均优于现有的SOTA（最先进）模型，同时大大降低了物理潜伏期。

随着自我监督学习的快速发展（例如，对比度学习），在医学图像分析中广泛认识到具有大规模图像（即使没有注释）来训练更具概括的AI模型的重要性。但是，大规模收集大规模任务的未注释数据对于单个实验室来说可能具有挑战性。现有的在线资源（例如数字书籍，出版物和搜索引擎）为获取大型图像提供了新的资源。然而，在医疗保健中发布的图像（例如放射学和病理学）由大量的带有子图的复合图组成。为了提取和分离化合物形象为下游学习的可用单个图像，我们提出了一个简单的复合图分离（SIMCFS）框架，而无需使用传统所需的检测边界框注释，并具有新的损失函数和硬案例模拟。我们的技术贡献是四倍：（1）我们引入了一个基于模拟的培训框架，该框架最小化了对资源广泛的边界框注释的需求； （2）我们提出了一种新的侧损失，可针对复合人物分离进行优化； （3）我们提出了一种阶层内图像增强方法来模拟硬病例； （4）据我们所知，这是第一项评估利用复合图像分离的自我监督学习功效的研究。从结果来看，提出的SIMCF在ImageClef 2016复合人物分离数据库上实现了最先进的性能。使用大规模开采数字的预审预革的学习模型通过对比度学习算法提高了下游图像分类任务的准确性。 SIMCF的源代码可在https://github.com/hrlblab/imageseperation上公开获得。