We investigate ensemble methods for prediction in an online setting. Unlike all the literature in ensembling, for the first time, we introduce a new approach using a meta learner that effectively combines the base model predictions via using a superset of the features that is the union of the base models' feature vectors instead of the predictions themselves. Here, our model does not use the predictions of the base models as inputs to a machine learning algorithm, but choose the best possible combination at each time step based on the state of the problem. We explore three different constraint spaces for the ensembling of the base learners that linearly combines the base predictions, which are convex combinations where the components of the ensembling vector are all nonnegative and sum up to 1; affine combinations where the weight vector components are required to sum up to 1; and the unconstrained combinations where the components are free to take any real value. The constraints are both theoretically analyzed under known statistics and integrated into the learning procedure of the meta learner as a part of the optimization in an automated manner. To show the practical efficiency of the proposed method, we employ a gradient-boosted decision tree and a multi-layer perceptron separately as the meta learners. Our framework is generic so that one can use other machine learning architectures as the ensembler as long as they allow for a custom differentiable loss for minimization. We demonstrate the learning behavior of our algorithm on synthetic data and the significant performance improvements over the conventional methods over various real life datasets, extensively used in the well-known data competitions. Furthermore, we openly share the source code of the proposed method to facilitate further research and comparison.

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.

延迟的诊断联合性不稳定会导致踝关节的显着发病和关节炎的加速变化。使用3D体积测量值，重量计算机断层扫描（WBCT）已显示出有希望的早期和可靠检测分离出的集团不稳定性的潜力。尽管据报道这些测量值高度准确，但它们也依赖于经验，耗时，并且需要一种特定的3D测量软件工具，该工具导致临床医生仍然对传统的诊断方法表现出更大的兴趣。这项研究的目的是通过使用WBCT扫描来自动化3D体积解剖结构的3D体积评估来提高准确性，加速分析时间并减少观察者间偏置。我们使用了先前收集的单侧联合不稳定性患者的WBCT扫描进行了回顾性研究。评估了144个双侧踝WBCT扫描（48个不稳定，96个对照）。我们开发了三个深度学习（DL）模型，用于分析WBCT扫描以识别集团不稳定性。这三个模型包括两个最先进的模型（模型1-3D卷积神经网络[CNN]和具有长短期内存[LSTM]的模型2-CNN）和一个新的模型（模型3-差分差异我们在这项研究中介绍的CNN LSTM）。模型1未能分析WBCT扫描（F1得分= 0）。模型2仅错误分类两种情况（F1得分= 0.80）。模型3的表现优于模型2，并实现了几乎完美的性能，在对照组中仅误导了一个情况（F1得分= 0.91），因为不稳定，而比模型2更快。

在过去的几年里，几年枪支学习（FSL）引起了极大的关注，以最大限度地减少标有标记的训练示例的依赖。FSL中固有的困难是处理每个课程的培训样本太少的含糊不清的歧义。为了在FSL中解决这一基本挑战，我们的目标是培训可以利用关于新颖类别的先前语义知识来引导分类器合成过程的元学习模型。特别是，我们提出了语义调节的特征注意力和样本注意机制，估计表示尺寸和培训实例的重要性。我们还研究了FSL的样本噪声问题，以便在更现实和不完美的环境中利用Meta-Meverys。我们的实验结果展示了所提出的语义FSL模型的有效性，而没有样品噪声。

就像其他少量学习问题一样，很少拍摄的细分旨在最大限度地减少手动注释的需求，这在分割任务中特别昂贵。即使少量拍摄设置降低了新型测试类的这种成本，仍然需要注释培训数据。为了减轻这种需求，我们提出了一种自我监督的培训方法，用于学习几次射门分割模型。我们首先使用无监督的显着性估计来获得图像上的伪掩码。然后，我们将在不同的伪掩模的不同分割和增强图像的不同分裂上培训一个简单的原型模型。我们广泛的实验表明，该方法达到了有希望的结果，突出了自我监督培训的潜力。据我们所知，这是第一个解决自然图像上无监督的少量分割问题的第一项工作。

普通射线照相被广泛用于检测总髋关节置换（THR）植入物的机械松动。目前，X光片是由医疗专业人员手动评估的，这可能是差的，并且观察者内部可靠性和准确性较低。此外，手动检测THR植入物的机械松动需要经验丰富的临床医生，这些临床医生可能总是很容易获得，可能导致诊断延迟。在这项研究中，我们提出了一种新型的，全自动和可解释的方法，用于使用深卷积神经网络（CNN）从纯X线照片中检测THR植入物的机械松动。我们使用五倍交叉验证对40名患者进行了40名患者的CNN培训，并将其性能与大量板认证的骨科医生（AFC）进行了比较。为了提高对机器结局的信心，我们还实施了显着图，以可视化CNN在哪里进行诊断。 CNN在诊断植入物的机械松动方面优于骨科医生，其敏感性明显高于敏感性（0.94），其特异性相同（0.96）（0.96）。显着图显示，CNN着眼于临床相关的特征以进行诊断。此类CNN可用于自动放射植入物的机械松动，以补充从业者的决策过程，提高其诊断准确性，并释放它们以进行以患者为中心的护理。