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In recent years, anomaly detection has become an essential field in medical image analysis. Most current anomaly detection methods for medical images are based on image reconstruction. In this work, we propose a novel anomaly detection…

Computer Vision and Pattern Recognition · Computer Science 2023-01-20 Florentin Bieder , Julia Wolleb , Robin Sandkühler , Philippe C. Cattin

Anomaly detection is concerned with identifying data patterns that deviate remarkably from the expected behaviour. This is an important research problem, due to its broad set of application domains, from data analysis to e-health,…

Machine Learning · Computer Science 2021-08-23 L. Erhan , M. Ndubuaku , M. Di Mauro , W. Song , M. Chen , G. Fortino , O. Bagdasar , A. Liotta

System states that are anomalous from the perspective of a domain expert occur frequently in some anomaly detection problems. The performance of commonly used unsupervised anomaly detection methods may suffer in that setting, because they…

Machine Learning · Statistics 2016-05-17 Richard Neuberg , Yixin Shi

The key to out-of-distribution detection is density estimation of the in-distribution data or of its feature representations. This is particularly challenging for dense anomaly detection in domains where the in-distribution data has a…

Computer Vision and Pattern Recognition · Computer Science 2023-09-15 Silvio Galesso , Max Argus , Thomas Brox

Video anomaly detection is a challenging task not only because it involves solving many sub-tasks such as motion representation, object localization and action recognition, but also because it is commonly considered as an unsupervised…

Computer Vision and Pattern Recognition · Computer Science 2020-12-04 Yuqi Ouyang , Victor Sanchez

When using the K-nearest neighbors method, one often ignores uncertainty in the choice of K. To account for such uncertainty, Holmes and Adams (2002) proposed a Bayesian framework for K-nearest neighbors (KNN). Their Bayesian KNN (BKNN)…

Machine Learning · Statistics 2008-04-09 Wanhua Su , Hugh Chipman , Mu Zhu

How can we detect anomalies: that is, samples that significantly differ from a given set of high-dimensional data, such as images or sensor data? This is a practical problem with numerous applications and is also relevant to the goal of…

Machine Learning · Computer Science 2022-06-16 Adam Goodge , Bryan Hooi , See Kiong Ng , Wee Siong Ng

The main difficulty in high-dimensional anomaly detection tasks is the lack of anomalous data for training. And simply collecting anomalous data from the real world, common distributions, or the boundary of normal data manifold may face the…

Computer Vision and Pattern Recognition · Computer Science 2021-04-27 Songmin Dai , Jide Li , Lu Wang , Congcong Zhu , Yifan Wu , Xiaoqiang Li

This paper considers an anomaly detection problem in which a detection algorithm assigns anomaly scores to multi-dimensional data points, such as cellular networks' Key Performance Indicators (KPIs). We propose an optimization framework to…

Information Theory · Computer Science 2023-09-01 Ali Maatouk , Fadhel Ayed , Wenjie Li , Yu Wang , Hong Zhu , Jiantao Ye

The wide variety of in-distribution and out-of-distribution data in medical imaging makes universal anomaly detection a challenging task. Recently a number of self-supervised methods have been developed that train end-to-end models on…

Computer Vision and Pattern Recognition · Computer Science 2022-09-05 Matthew Baugh , Jeremy Tan , Athanasios Vlontzos , Johanna P. Müller , Bernhard Kainz

Existing methods for retrieving k-nearest neighbours suffer from the curse of dimensionality. We argue this is caused in part by inherent deficiencies of space partitioning, which is the underlying strategy used by most existing methods. We…

Data Structures and Algorithms · Computer Science 2017-04-07 Ke Li , Jitendra Malik

Unsupervised anomaly localization aims to identify anomalous regions that deviate from normal sample patterns. Most recent methods perform feature matching or reconstruction for the target sample with pre-trained deep neural networks.…

Computer Vision and Pattern Recognition · Computer Science 2026-04-15 Katsuya Hotta , Chao Zhang , Yoshihiro Hagihara , Takuya Akashi

K-nearest neighbors (KNN) is one of the earliest and most established algorithms in machine learning. For regression tasks, KNN averages the targets within a neighborhood which poses a number of challenges: the neighborhood definition is…

Machine Learning · Computer Science 2022-05-18 Youssef Nader , Leon Sixt , Tim Landgraf

Anomaly detection is a significant and hence well-studied problem. However, developing effective anomaly detection methods for complex and high-dimensional data remains a challenge. As Generative Adversarial Networks (GANs) are able to…

Machine Learning · Computer Science 2018-12-07 Houssam Zenati , Manon Romain , Chuan Sheng Foo , Bruno Lecouat , Vijay Ramaseshan Chandrasekhar

Anomaly detection is an important problem that has been well-studied within diverse research areas and application domains. The aim of this survey is two-fold, firstly we present a structured and comprehensive overview of research methods…

Machine Learning · Computer Science 2019-01-24 Raghavendra Chalapathy , Sanjay Chawla

This paper presents a new approach, based on polynomial optimization and the method of moments, to the problem of anomaly detection. The proposed technique only requires information about the statistical moments of the normal-state…

Optimization and Control · Mathematics 2015-06-02 Jose A. Lopez , Octavia Camps , Mario Sznaier

In point-based sensing systems such as coordinate measuring machines (CMM) and laser ultrasonics where complete sensing is impractical due to the high sensing time and cost, adaptive sensing through a systematic exploration is vital for…

Machine Learning · Statistics 2019-10-08 Hao Yan , Kamran Paynabar , Jianjun Shi

Existing representation-based methods usually conduct industrial anomaly detection in two stages: obtain feature representations with a pre-trained model and perform distance measures for anomaly detection. Among them, K-nearest neighbor…

Computer Vision and Pattern Recognition · Computer Science 2024-05-20 Shuai Lyu , Dongmei Mo , Waikeung Wong

K-Nearest Neighbours (k-NN) is a popular classification and regression algorithm, yet one of its main limitations is the difficulty in choosing the number of neighbours. We present a Bayesian algorithm to compute the posterior probability…

Machine Learning · Computer Science 2017-06-05 Giuseppe Nuti

Detecting anomalies in traffic scenes is crucial for ensuring safety in autonomous driving, yet collecting representative anomalous data remains challenging. Existing anomaly detection methods are highly specialized and rely on normality as…

Computer Vision and Pattern Recognition · Computer Science 2026-05-20 Albert Schotschneider , Daniel Bogdoll , Svetlana Pavlitska , Ahmed Abouelazm , Johann Marius Zoellner