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About

About

Helena Montenegro obtained a M.Sc. degree in informatics and computing engineering from the Faculty of Engineering of the University of Porto in 2021. She is a Ph.D. student in informatics engineering and a research assistant at INESC TEC, associated with the Visual Computing and Machine Intelligence Group (VCMI). Her main research interests include Machine Learning and Computer Vision, with a special focus on privacy-preserving methods for visual data and interpretability.

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Details

Details

  • Name

    Helena Montenegro
  • Role

    Research Assistant
  • Since

    05th November 2020
002
Publications

2025

Leveraging Cold Diffusion for the Decomposition of Identically Distributed Superimposed Images

Authors
Montenegro, H; Cardoso, JS;

Publication
IEEE OPEN JOURNAL OF SIGNAL PROCESSING

Abstract
With the growing adoption of Deep Learning for imaging tasks in biometrics and healthcare, it becomes increasingly important to ensure privacy when using and sharing images of people. Several works enable privacy-preserving image sharing by anonymizing the images so that the corresponding individuals are no longer recognizable. Most works average images or their embeddings as an anonymization technique, relying on the assumption that the average operation is irreversible. Recently, cold diffusion models, based on the popular denoising diffusion probabilistic models, have succeeded in reversing deterministic transformations on images. In this work, we leverage cold diffusion to decompose superimposed images, empirically demonstrating that it is possible to obtain two or more identically-distributed images given their average. We propose novel sampling strategies for this task and show their efficacy on three datasets. Our findings highlight the risks of averaging images as an anonymization technique and argue for the use of alternative anonymization strategies.

2024

Anonymizing medical case-based explanations through disentanglement

Authors
Montenegro, H; Cardoso, JS;

Publication
MEDICAL IMAGE ANALYSIS

Abstract
Case-based explanations are an intuitive method to gain insight into the decision-making process of deep learning models in clinical contexts. However, medical images cannot be shared as explanations due to privacy concerns. To address this problem, we propose a novel method for disentangling identity and medical characteristics of images and apply it to anonymize medical images. The disentanglement mechanism replaces some feature vectors in an image while ensuring that the remaining features are preserved, obtaining independent feature vectors that encode the images' identity and medical characteristics. We also propose a model to manufacture synthetic privacy-preserving identities to replace the original image's identity and achieve anonymization. The models are applied to medical and biometric datasets, demonstrating their capacity to generate realistic-looking anonymized images that preserve their original medical content. Additionally, the experiments show the network's inherent capacity to generate counterfactual images through the replacement of medical features.

2024

REPRODUCING ASYMMETRIES CAUSED BY BREAST CANCER TREATMENT IN PRE-OPERATIVE BREAST IMAGES

Authors
Freitas, N; Montenegro, H; Cardoso, MJ; Cardoso, JS;

Publication
IEEE INTERNATIONAL SYMPOSIUM ON BIOMEDICAL IMAGING, ISBI 2024

Abstract
Breast cancer locoregional treatment causes alterations to the physical aspect of the breast, often negatively impacting the self-esteem of patients unaware of the possible aesthetic outcomes of those treatments. To improve patients' self-esteem and enable a more informed choice of treatment when multiple options are available, the possibility to predict how the patient might look like after surgery would be of invaluable help. However, no work has been proposed to predict the aesthetic outcomes of breast cancer treatment. As a first step, we compare traditional computer vision and deep learning approaches to reproduce asymmetries of post-operative patients on pre-operative breast images. The results suggest that the traditional approach is better at altering the contour of the breast. In contrast, the deep learning approach succeeds in realistically altering the position and direction of the nipple.