MAD-AD: Masked Diffusion for Unsupervised Brain Anomaly Detection

Fuente: arXiv
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Auteurs principaux: Beizaee, Farzad, Lodygensky, Gregory, Desrosiers, Christian, Dolz, Jose
Format: Preprint
Publié: 2025
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author Beizaee, Farzad
Lodygensky, Gregory
Desrosiers, Christian
Dolz, Jose
author_facet Beizaee, Farzad
Lodygensky, Gregory
Desrosiers, Christian
Dolz, Jose
contents 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 complexity and variability of brain structures and the scarcity of annotated abnormal data. To address this challenge, we propose a novel approach that incorporates masking within diffusion models, leveraging their generative capabilities to learn robust representations of normal brain anatomy. During training, our model processes only normal brain MRI scans and performs a forward diffusion process in the latent space that adds noise to the features of randomly-selected patches. Following a dual objective, the model learns to identify which patches are noisy and recover their original features. This strategy ensures that the model captures intricate patterns of normal brain structures while isolating potential anomalies as noise in the latent space. At inference, the model identifies noisy patches corresponding to anomalies and generates a normal counterpart for these patches by applying a reverse diffusion process. Our method surpasses existing unsupervised anomaly detection techniques, demonstrating superior performance in generating accurate normal counterparts and localizing anomalies. The code is available at hhttps://github.com/farzad-bz/MAD-AD.
format Preprint
id arxiv_https___arxiv_org_abs_2502_16943
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle MAD-AD: Masked Diffusion for Unsupervised Brain Anomaly Detection
Beizaee, Farzad
Lodygensky, Gregory
Desrosiers, Christian
Dolz, Jose
Computer Vision and Pattern Recognition
Image and Video Processing
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 complexity and variability of brain structures and the scarcity of annotated abnormal data. To address this challenge, we propose a novel approach that incorporates masking within diffusion models, leveraging their generative capabilities to learn robust representations of normal brain anatomy. During training, our model processes only normal brain MRI scans and performs a forward diffusion process in the latent space that adds noise to the features of randomly-selected patches. Following a dual objective, the model learns to identify which patches are noisy and recover their original features. This strategy ensures that the model captures intricate patterns of normal brain structures while isolating potential anomalies as noise in the latent space. At inference, the model identifies noisy patches corresponding to anomalies and generates a normal counterpart for these patches by applying a reverse diffusion process. Our method surpasses existing unsupervised anomaly detection techniques, demonstrating superior performance in generating accurate normal counterparts and localizing anomalies. The code is available at hhttps://github.com/farzad-bz/MAD-AD.
title MAD-AD: Masked Diffusion for Unsupervised Brain Anomaly Detection
topic Computer Vision and Pattern Recognition
Image and Video Processing
url https://arxiv.org/abs/2502.16943