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Unsupervised anomaly detection in brain images is crucial for identifying injuries and pathologies without access to labels. However, the accurate localization of anomalies in medical images remains challenging due to the inherent…

Computer Vision and Pattern Recognition · Computer Science 2025-07-25 Farzad Beizaee , Gregory Lodygensky , Christian Desrosiers , Jose Dolz

We consider the paradigm of unsupervised anomaly detection, which involves the identification of anomalies within a dataset in the absence of labeled examples. Though distance-based methods are top-performing for unsupervised anomaly…

Machine Learning · Statistics 2025-08-04 Yuchao Cai , Hanfang Yang , Yuheng Ma , Hanyuan Hang

The core challenge in unsupervised anomaly detection is identifying abnormal patterns without prior knowledge of their characteristics. While existing methods have addressed aspects of this problem, they often struggle to learn a robust…

Machine Learning · Computer Science 2026-05-12 Prithul Sarker , Sushmita Sarker , Nicholas G. Murray , Alireza Tavakkoli

Unsupervised anomaly detection aims to build models to effectively detect unseen anomalies by only training on the normal data. Although previous reconstruction-based methods have made fruitful progress, their generalization ability is…

Machine Learning · Computer Science 2022-01-04 Yuxin Zhang , Jindong Wang , Yiqiang Chen , Han Yu , Tao Qin

Unsupervised Anomaly Detection (UAD) plays a crucial role in identifying abnormal patterns within data without labeled examples, holding significant practical implications across various domains. Although the individual contributions of…

Machine Learning · Computer Science 2024-06-04 Zeyu Fang , Ming Gu , Sheng Zhou , Jiawei Chen , Qiaoyu Tan , Haishuai Wang , Jiajun Bu

The ongoing challenges in time series anomaly detection (TSAD), notably the scarcity of anomaly labels and the variability in anomaly lengths and shapes, have led to the need for a more efficient solution. As limited anomaly labels hinder…

Machine Learning · Computer Science 2023-11-28 Yuting Sun , Guansong Pang , Guanhua Ye , Tong Chen , Xia Hu , Hongzhi Yin

Anomaly detection (AD) is a crucial task in machine learning with various applications, such as detecting emerging diseases, identifying financial frauds, and detecting fake news. However, obtaining complete, accurate, and precise labels…

Machine Learning · Computer Science 2023-02-10 Minqi Jiang , Chaochuan Hou , Ao Zheng , Xiyang Hu , Songqiao Han , Hailiang Huang , Xiangnan He , Philip S. Yu , Yue Zhao

Dynamic graph anomaly detection (DGAD) is critical for many real-world applications but remains challenging due to the scarcity of labeled anomalies. Existing methods are either unsupervised or semi-supervised: unsupervised methods avoid…

Machine Learning · Computer Science 2026-02-24 Yuxing Tian , Yiyan Qi , Fengran Mo , Weixu Zhang , Jian Guo , Jian-Yun Nie

Unsupervised anomaly detection (UAD) aims to find anomalous images by optimising a detector using a training set that contains only normal images. UAD approaches can be based on reconstruction methods, self-supervised approaches, and…

Image and Video Processing · Electrical Eng. & Systems 2023-08-23 Yu Tian , Guansong Pang , Yuyuan Liu , Chong Wang , Yuanhong Chen , Fengbei Liu , Rajvinder Singh , Johan W Verjans , Mengyu Wang , Gustavo Carneiro

Deep anomaly detection models using a supervised mode of learning usually work under a closed set assumption and suffer from overfitting to previously seen rare anomalies at training, which hinders their applicability in a real scenario. In…

Image and Video Processing · Electrical Eng. & Systems 2020-10-26 Behzad Bozorgtabar , Dwarikanath Mahapatra , Guillaume Vray , Jean-Philippe Thiran

Anomaly Detection (AD) is a critical task that involves identifying observations that do not conform to a learned model of normality. Prior work in deep AD is predominantly based on a familiarity hypothesis, where familiar features serve as…

Machine Learning · Computer Science 2024-02-27 Sarath Sivaprasad , Mario Fritz

Anomaly detection is an important task for complex systems (e.g., industrial facilities, manufacturing, large-scale science experiments), where failures in a sub-system can lead to low yield, faulty products, or even damage to components.…

Machine Learning · Computer Science 2023-09-06 Ryan Humble , Zhe Zhang , Finn O'Shea , Eric Darve , Daniel Ratner

Unsupervised anomaly detection and localization, as of one the most practical and challenging problems in computer vision, has received great attention in recent years. From the time the MVTec AD dataset was proposed to the present, new…

Computer Vision and Pattern Recognition · Computer Science 2022-05-31 Ye Zheng , Xiang Wang , Yu Qi , Wei Li , Liwei Wu

One pivot challenge for image anomaly (AD) detection is to learn discriminative information only from normal class training images. Most image reconstruction based AD methods rely on the discriminative capability of reconstruction error.…

Computer Vision and Pattern Recognition · Computer Science 2020-07-21 Dongyun Lin , Yiqun Li , Shudong Xie , Tin Lay Nwe , Sheng Dong

Unsupervised learning of feature representations is a challenging yet important problem for analyzing a large collection of multimedia data that do not have semantic labels. Recently proposed neural network-based unsupervised learning…

Computer Vision and Pattern Recognition · Computer Science 2022-11-15 Takahiko Furuya , Ryutarou Ohbuchi

Unsupervised anomaly detection (UAD) aims to detect anomalies without labeled data, a necessity in many machine learning applications where anomalous samples are rare or not available. Most state-of-the-art methods fall into two categories:…

Machine Learning · Computer Science 2025-07-30 Nicolas Pinon , Carole Lartizien

Unsupervised anomaly detection (UAD) is a widely adopted approach in industry due to rare anomaly occurrences and data imbalance. A desirable characteristic of an UAD model is contained generalization ability which excels in the…

Computer Vision and Pattern Recognition · Computer Science 2023-08-29 YeongHyeon Park , Sungho Kang , Myung Jin Kim , Hyeonho Jeong , Hyunkyu Park , Hyeong Seok Kim , Juneho Yi

Medical image anomaly detection faces unique challenges due to subtle, heterogeneous anomalies embedded in complex anatomical structures. Through systematic Grad-CAM analysis, we reveal that discriminative activation maps fail on medical…

Computer Vision and Pattern Recognition · Computer Science 2026-03-10 Xijun Lu , Hongying Liu , Fanhua Shang , Yanming Hui , Liang Wan

Unsupervised Continuous Anomaly Detection (UCAD) is gaining attention for effectively addressing the catastrophic forgetting and heavy computational burden issues in traditional Unsupervised Anomaly Detection (UAD). However, existing UCAD…

Computer Vision and Pattern Recognition · Computer Science 2026-03-24 Mingle Zhou , Jiahui Liu , Jin Wan , Gang Li , Min Li

The widespread adoption of digital services, along with the scale and complexity at which they operate, has made incidents in IT operations increasingly more likely, diverse, and impactful. This has led to the rapid development of a central…

Machine Learning · Computer Science 2025-04-01 Vincent Jacob , Yanlei Diao