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.

Timely and effective feedback within surgical training plays a critical role in developing the skills required to perform safe and efficient surgery. Feedback from expert surgeons, while especially valuable in this regard, is challenging to acquire due to their typically busy schedules, and may be subject to biases. Formal assessment procedures like OSATS and GEARS attempt to provide objective measures of skill, but remain time-consuming. With advances in machine learning there is an opportunity for fast and objective automated feedback on technical skills. The SimSurgSkill 2021 challenge (hosted as a sub-challenge of EndoVis at MICCAI 2021) aimed to promote and foster work in this endeavor. Using virtual reality (VR) surgical tasks, competitors were tasked with localizing instruments and predicting surgical skill. Here we summarize the winning approaches and how they performed. Using this publicly available dataset and results as a springboard, future work may enable more efficient training of surgeons with advances in surgical data science. The dataset can be accessed from https://console.cloud.google.com/storage/browser/isi-simsurgskill-2021.

Artificial Intelligence (AI) is having a tremendous impact across most areas of science. Applications of AI in healthcare have the potential to improve our ability to detect, diagnose, prognose, and intervene on human disease. For AI models to be used clinically, they need to be made safe, reproducible and robust, and the underlying software framework must be aware of the particularities (e.g. geometry, physiology, physics) of medical data being processed. This work introduces MONAI, a freely available, community-supported, and consortium-led PyTorch-based framework for deep learning in healthcare. MONAI extends PyTorch to support medical data, with a particular focus on imaging, and provide purpose-specific AI model architectures, transformations and utilities that streamline the development and deployment of medical AI models. MONAI follows best practices for software-development, providing an easy-to-use, robust, well-documented, and well-tested software framework. MONAI preserves the simple, additive, and compositional approach of its underlying PyTorch libraries. MONAI is being used by and receiving contributions from research, clinical and industrial teams from around the world, who are pursuing applications spanning nearly every aspect of healthcare.

生物医学图像分析算法验证取决于参考数据集的高质量注释，标记指令是关键。尽管它们的重要性，但他们的优化仍然没有得到探索。在这里，我们介绍了对标签指令及其对该领域注释质量的影响的首次系统研究。通过对Miccai协会注册的专业实践和国际比赛的全面检查，我们发现了注释者对标签说明的标签需求及其当前质量和可用性之间的差异。基于对156家专业公司的156个注释者和708个亚马逊机械土耳其人（MTURK）人群的注释者的14040张图像的分析，使用具有不同信息密度级别的说明，我们进一步发现，包括示例性图像与文本描述，唯一的描述，示例性图像显着增强了注释性能，虽然仅扩展文本说明并非如此。最后，专业注释者不断优于mturk人群。我们的研究提高了对生物医学图像分析标签指令中质量标准的需求的认识。

自动生物医学图像分析的领域至关重要地取决于算法验证的可靠和有意义的性能指标。但是，当前的度量使用通常是不明智的，并且不能反映基本的域名。在这里，我们提出了一个全面的框架，该框架指导研究人员以问题意识的方式选择绩效指标。具体而言，我们专注于生物医学图像分析问题，这些问题可以解释为图像，对象或像素级别的分类任务。该框架首先编译域兴趣 - 目标结构 - ，数据集和算法与输出问题相关的属性的属性与问题指纹相关，同时还将其映射到适当的问题类别，即图像级分类，语义分段，实例，实例细分或对象检测。然后，它指导用户选择和应用一组适当的验证指标的过程，同时使他们意识到与个人选择相关的潜在陷阱。在本文中，我们描述了指标重新加载推荐框架的当前状态，目的是从图像分析社区获得建设性的反馈。当前版本是在由60多个图像分析专家的国际联盟中开发的，将在社区驱动的优化之后公开作为用户友好的工具包提供。

机器学习方法利用多参数生物标志物，特别是基于神经影像动物，具有改善痴呆早期诊断的巨大潜力，并预测哪些个体存在发展痴呆的风险。对于机器学习领域的基准算法和痴呆症中的神经影像症，并评估他们在临床实践中使用的潜力和临床试验，七年的大挑战已经在过去十年中组织：Miriad，Alzheimer的疾病大数据梦，Caddementia，机器学习挑战，MCI神经影像动物，蝌蚪和预测分析竞争。基于两个挑战评估框架，我们分析了这些大挑战如何互相补充研究问题，数据集，验证方法，结果和影响。七个大挑战解决了与（临床前）痴呆症（临床）痴呆症的筛查，诊断，预测和监测有关的问题。临床问题，任务和性能指标几乎没有重叠。然而，这具有提供对广泛问题的洞察力的优势，它也会限制对挑战的结果的验证。通常，获胜算法执行严格的数据预处理并组合了广泛的输入特征。尽管最先进的表演，但临床上没有挑战评估的大部分方法。为了增加影响，未来的挑战可以更加关注统计分析，对其与高于阿尔茨海默病的临床问题，以及使用超越阿尔茨海默病神经影像疾病的临床问题，以及超越阿尔茨海默病的临床问题。鉴于过去十年中汲取的潜力和经验教训，我们在未来十年及其超越的机器学习和神经影像中的大挑战前景兴奋。

语义图像分割是手术中的背景知识和自治机器人的重要前提。本领域的状态专注于在微创手术期间获得的传统RGB视频数据，但基于光谱成像数据的全景语义分割并在开放手术期间获得几乎没有注意到日期。为了解决文献中的这种差距，我们正在研究基于在开放手术环境中获得的猪的高光谱成像（HSI）数据的以下研究问题：（1）基于神经网络的HSI数据的充分表示是完全自动化的器官分割，尤其是关于数据的空间粒度（像素与Superpixels与Patches与完整图像）的空间粒度？ （2）在执行语义器官分割时，是否有利用HSI数据使用HSI数据，即RGB数据和处理的HSI数据（例如氧合等组织参数）？根据基于20猪的506个HSI图像的全面验证研究，共注释了19个类，基于深度的学习的分割性能 - 贯穿模态 - 与输入数据的空间上下文一致。未处理的HSI数据提供优于RGB数据或来自摄像机提供商的处理数据，其中优势随着输入到神经网络的输入的尺寸而增加。最大性能（应用于整个图像的HSI）产生了0.89（标准偏差（SD）0.04）的平均骰子相似度系数（DSC），其在帧间间变异性（DSC为0.89（SD 0.07）的范围内。我们得出结论，HSI可以成为全自动手术场景理解的强大的图像模型，其具有传统成像的许多优点，包括恢复额外功能组织信息的能力。

尽管自动图像分析的重要性不断增加，但最近的元研究揭示了有关算法验证的主要缺陷。性能指标对于使用的自动算法的有意义，客观和透明的性能评估和验证尤其是关键，但是在使用特定的指标进行给定的图像分析任务时，对实际陷阱的关注相对较少。这些通常与（1）无视固有的度量属性，例如在存在类不平衡或小目标结构的情况下的行为，（2）无视固有的数据集属性，例如测试的非独立性案例和（3）无视指标应反映的实际生物医学领域的兴趣。该动态文档的目的是说明图像分析领域通常应用的性能指标的重要局限性。在这种情况下，它重点介绍了可以用作图像级分类，语义分割，实例分割或对象检测任务的生物医学图像分析问题。当前版本是基于由全球60多家机构的国际图像分析专家进行的关于指标的Delphi流程。

Variance parameter estimation in linear mixed models is a challenge for many classical nonlinear optimization algorithms due to the positive-definiteness constraint of the random effects covariance matrix. We take a completely novel view on parameter estimation in linear mixed models by exploiting the intrinsic geometry of the parameter space. We formulate the problem of residual maximum likelihood estimation as an optimization problem on a Riemannian manifold. Based on the introduced formulation, we give geometric higher-order information on the problem via the Riemannian gradient and the Riemannian Hessian. Based on that, we test our approach with Riemannian optimization algorithms numerically. Our approach yields a higher quality of the variance parameter estimates compared to existing approaches.

Given ample experimental data from a system governed by differential equations, it is possible to use deep learning techniques to construct the underlying differential operators. In this work we perform symbolic discovery of differential operators in a situation where there is sparse experimental data. This small data regime in machine learning can be made tractable by providing our algorithms with prior information about the underlying dynamics. Physics Informed Neural Networks (PINNs) have been very successful in this regime (reconstructing entire ODE solutions using only a single point or entire PDE solutions with very few measurements of the initial condition). We modify the PINN approach by adding a neural network that learns a representation of unknown hidden terms in the differential equation. The algorithm yields both a surrogate solution to the differential equation and a black-box representation of the hidden terms. These hidden term neural networks can then be converted into symbolic equations using symbolic regression techniques like AI Feynman. In order to achieve convergence of these neural networks, we provide our algorithms with (noisy) measurements of both the initial condition as well as (synthetic) experimental data obtained at later times. We demonstrate strong performance of this approach even when provided with very few measurements of noisy data in both the ODE and PDE regime.