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Bercea, C.-I. ; Rueckert, D.* ; Schnabel, J.A.

What Do AEs Learn? Challenging Common Assumptions in Unsupervised Anomaly Detection.

In: (Medical Image Computing and Computer Assisted Intervention – MICCAI 2023). Berlin [u.a.]: Springer, 2023. 304-314 (Lect. Notes Comput. Sc. ; 14224 LNCS)
DOI
Detecting abnormal findings in medical images is a critical task that enables timely diagnoses, effective screening, and urgent case prioritization. Autoencoders (AEs) have emerged as a popular choice for anomaly detection and have achieved state-of-the-art (SOTA) performance in detecting pathology. However, their effectiveness is often hindered by the assumption that the learned manifold only contains information that is important for describing samples within the training distribution. In this work, we challenge this assumption and investigate what AEs actually learn when they are posed to solve anomaly detection tasks. We have found that standard, variational, and recent adversarial AEs are generally not well-suited for pathology detection tasks where the distributions of normal and abnormal strongly overlap. In this work, we propose MorphAEus, novel deformable AEs to produce pseudo-healthy reconstructions refined by estimated dense deformation fields. Our approach improves the learned representations, leading to more accurate reconstructions, reduced false positives and precise localization of pathology. We extensively validate our method on two public datasets and demonstrate SOTA performance in detecting pneumonia and COVID-19. Code: https://github.com/ci-ber/MorphAEus.
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Publication type Article: Conference contribution
Corresponding Author
Keywords Anomaly Detection ; Representation Learning
ISSN (print) / ISBN 0302-9743
e-ISSN 1611-3349
Conference Title Medical Image Computing and Computer Assisted Intervention – MICCAI 2023
Journal Lecture Notes in Computer Science
Quellenangaben Volume: 14224 LNCS, Issue: , Pages: 304-314 Article Number: , Supplement: ,
Publisher Springer
Publishing Place Berlin [u.a.]
Non-patent literature Publications
Institute(s) Institute for Machine Learning in Biomed Imaging (IML)
Helmholtz Artifical Intelligence Cooperation Unit (HAICU)
Grants Helmholtz Association under the joint research school "Munich School for Data Science -MUDS"