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Unsupervised learning can discover various unseen abnormalities, relying on large-scale unannotated medical images of healthy subjects. Towards this, unsupervised methods reconstruct a 2D/3D single medical image to detect outliers either in…

Computer Vision and Pattern Recognition · Computer Science 2020-10-13 Changhee Han , Leonardo Rundo , Kohei Murao , Tomoyuki Noguchi , Yuki Shimahara , Zoltan Adam Milacski , Saori Koshino , Evis Sala , Hideki Nakayama , Shinichi Satoh

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

Unsupervised anomaly detection (UAD) plays an important role in modern data analytics and it is crucial to provide simple yet effective and guaranteed UAD algorithms for real applications. In this paper, we present a novel UAD method for…

Machine Learning · Computer Science 2024-12-17 Wei Dai , Kai Hwang , Jicong Fan

Anomaly detection in complex, high-dimensional data, such as UAV sensor readings, is essential for operational safety but challenging for existing methods due to their limited sensitivity, scalability, and inability to capture intricate…

Machine Learning · Computer Science 2025-10-28 Mingze Gong , Juan Du , Jianbang You

Responding to the challenge of detecting unusual radar targets in a well identified environment, innovative anomaly and novelty detection methods keep emerging in the literature. This work aims at presenting a benchmark gathering common and…

Signal Processing · Electrical Eng. & Systems 2021-06-22 Martin Bauw , Santiago Velasco-Forero , Jesus Angulo , Claude Adnet , Olivier Airiau

In medical imaging, obtaining large amounts of labeled data is often a hurdle, because annotations and pathologies are scarce. Anomaly detection is a method that is capable of detecting unseen abnormal data while only being trained on…

Computer Vision and Pattern Recognition · Computer Science 2022-06-09 Djennifer K. Madzia-Madzou , Hugo J. Kuijf

Heterogeneous dynamics commonly emerges in anomalous diffusion with intermittent transitions of diffusion states but proves challenging to identify using conventional statistical methods. To effectively capture these transient changes of…

Biological Physics · Physics 2024-01-24 Xiang Qu , Yi Hu , Wenjie Cai , Yang Xu , Hu Ke , Guolong Zhu , Zihan Huang

Anomaly detection is an emerging approach in digital pathology for its ability to efficiently and effectively utilize data for disease diagnosis. While supervised learning approaches deliver high accuracy, they rely on extensively annotated…

Image and Video Processing · Electrical Eng. & Systems 2025-08-22 Jiamu Wang , Keunho Byeon , Jinsol Song , Anh Nguyen , Sangjeong Ahn , Sung Hak Lee , Jin Tae Kwak

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 (AD) plays a vital role across a wide range of real-world domains by identifying data instances that deviate from expected patterns, potentially signaling critical events such as system failures, fraudulent activities, or…

Machine Learning · Computer Science 2025-07-11 Amirhossein Sadough , Mahyar Shahsavari , Mark Wijtvliet , Marcel van Gerven

We tackle unsupervised anomaly detection (UAD), a problem of detecting data that significantly differ from normal data. UAD is typically solved by using density estimation. Recently, deep neural network (DNN)-based density estimators, such…

Machine Learning · Statistics 2019-03-14 Masataka Yamaguchi , Yuma Koizumi , Noboru Harada

Automatic segmentation of brain abnormalities is challenging, as they vary considerably from one pathology to another. Current methods are supervised and require numerous annotated images for each pathology, a strenuous task. To tackle…

Image and Video Processing · Electrical Eng. & Systems 2021-01-27 Benjamin Lambert , Maxime Louis , Senan Doyle , Florence Forbes , Michel Dojat , Alan Tucholka

Detection of various lesions in brain MRI is clinically critical, but challenging due to the diversity of lesions and variability in imaging conditions. Current unsupervised learning methods detect anomalies mainly through reconstructing…

Computer Vision and Pattern Recognition · Computer Science 2025-12-29 Tao Yang , Xiuying Wang , Hao Liu , Guanzhong Gong , Lian-Ming Wu , Yu-Ping Wang , Lisheng Wang

Supervised machine learning has enabled accurate pathology detection in brain MRI, but requires training data from diseased subjects that may not be readily available in some scenarios, for example, in the case of rare diseases.…

Image and Video Processing · Electrical Eng. & Systems 2025-06-13 Ana Lawry Aguila , Peirong Liu , Oula Puonti , Juan Eugenio Iglesias

Anomaly detection (AD) is a crucial machine learning task that aims to learn patterns from a set of normal training samples to identify abnormal samples in test data. Most existing AD studies assume that the training and test data are drawn…

Computer Vision and Pattern Recognition · Computer Science 2023-09-06 Tri Cao , Jiawen Zhu , Guansong Pang

Anomaly detection (AD) is a critical task across domains such as cybersecurity and healthcare. In the unsupervised setting, an effective and theoretically-grounded principle is to train classifiers to distinguish normal data from…

Machine Learning · Statistics 2025-06-18 Matthew Lau , Tian-Yi Zhou , Xiangchi Yuan , Jizhou Chen , Wenke Lee , Xiaoming Huo

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

Universal anomaly detection still remains a challenging problem in machine learning and medical image analysis. It is possible to learn an expected distribution from a single class of normative samples, e.g., through epistemic uncertainty…

Computer Vision and Pattern Recognition · Computer Science 2023-10-03 Johanna P. Müller , Matthew Baugh , Jeremy Tan , Mischa Dombrowski , Bernhard Kainz

Medical anomaly detection is a crucial yet challenging task aimed at recognizing abnormal images to assist in diagnosis. Due to the high-cost annotations of abnormal images, most methods utilize only known normal images during training and…

Computer Vision and Pattern Recognition · Computer Science 2023-03-21 Yu Cai , Hao Chen , Xin Yang , Yu Zhou , Kwang-Ting Cheng

Congenital malformations of the brain are among the most common fetal abnormalities that impact fetal development. Previous anomaly detection methods on ultrasound images are based on supervised learning, rely on manual annotations, and…