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Publicações

Publicações por CTM

2025

A survey on cell nuclei instance segmentation and classification: Leveraging context and attention

Autores
Nunes, JD; Montezuma, D; Oliveira, D; Pereira, T; Cardoso, JS;

Publicação
MEDICAL IMAGE ANALYSIS

Abstract
Nuclear-derived morphological features and biomarkers provide relevant insights regarding the tumour microenvironment, while also allowing diagnosis and prognosis in specific cancer types. However, manually annotating nuclei from the gigapixel Haematoxylin and Eosin (H&E)-stained Whole Slide Images (WSIs) is a laborious and costly task, meaning automated algorithms for cell nuclei instance segmentation and classification could alleviate the workload of pathologists and clinical researchers and at the same time facilitate the automatic extraction of clinically interpretable features for artificial intelligence (AI) tools. But due to high intra- and inter-class variability of nuclei morphological and chromatic features, as well as H&Estains susceptibility to artefacts, state-of-the-art algorithms cannot correctly detect and classify instances with the necessary performance. In this work, we hypothesize context and attention inductive biases in artificial neural networks (ANNs) could increase the performance and generalization of algorithms for cell nuclei instance segmentation and classification. To understand the advantages, use-cases, and limitations of context and attention-based mechanisms in instance segmentation and classification, we start by reviewing works in computer vision and medical imaging. We then conduct a thorough survey on context and attention methods for cell nuclei instance segmentation and classification from H&E-stained microscopy imaging, while providing a comprehensive discussion of the challenges being tackled with context and attention. Besides, we illustrate some limitations of current approaches and present ideas for future research. As a case study, we extend both a general (Mask-RCNN) and a customized (HoVer-Net) instance segmentation and classification methods with context- and attention-based mechanisms and perform a comparative analysis on a multicentre dataset for colon nuclei identification and counting. Although pathologists rely on context at multiple levels while paying attention to specific Regions of Interest (RoIs) when analysing and annotating WSIs, our findings suggest translating that domain knowledge into algorithm design is no trivial task, but to fully exploit these mechanisms in ANNs, the scientific understanding of these methods should first be addressed.

2025

Unimodal Distributions for Ordinal Regression

Autores
Cardoso, JS; Cruz, RPM; Albuquerque, T;

Publicação
IEEE Trans. Artif. Intell.

Abstract
In many real-world prediction tasks, the class labels contain information about the relative order between the labels that are not captured by commonly used loss functions such as multicategory cross-entropy. In ordinal regression, many works have incorporated ordinality into models and loss functions by promoting unimodality of the probability output. However, current approaches are based on heuristics, particularly nonparametric ones, which are still insufficiently explored in the literature. We analyze the set of unimodal distributions in the probability simplex, establishing fundamental properties and giving new perspectives to understand the ordinal regression problem. Two contributions are then proposed to incorporate the preference for unimodal distributions into the predictive model: 1) UnimodalNet, a new architecture that by construction ensures the output is a unimodal distribution, and 2) Wasserstein regularization, a new loss term that relies on the notion of projection in a set to promote unimodality. Experiments show that the new architecture achieves top performance, while the proposed new loss term is very competitive while maintaining high unimodality.

2025

Beyond Accuracy: The Role of Calibration in Computational Pathology

Autores
Nunes, JD; Montezuma, D; Oliveira, D; Pereira, T; Zlobec, I; Cardoso, JS;

Publicação
2025 INTERNATIONAL JOINT CONFERENCE ON NEURAL NETWORKS, IJCNN

Abstract
Deep learning in computational pathology (CPath) has rapidly advanced in recent years. Research has primarily focused on enhancing accuracy and interpretability across various histology image analysis tasks, from tile-level to slide-level foundation models and novel multiple instance learning (MIL) strategies. However, it is equally important for models to provide well-calibrated confidence estimates. Due to factors such as dataset bias, overfitting, and limited training data, existing models tend to be overly confident on test sets. Promising solutions to address this issue include temperature scaling, a post-hoc method that adjusts logits using a single scalar value. However, the role of calibration in CPath is yet to be clarified. In this study, we evaluate temperature scaling and linear temperature scaling for CPath tasks, analyzing their impact on recalibration in both in-domain and out-of-domain distributions. The results show the limitations of current probability calibration techniques and motivate future work.

2025

H&E to IHC virtual staining methods in breast cancer: an overview and benchmarking

Autores
Klöckner, P; Teixeira, J; Montezuma, D; Fraga, J; Horlings, HM; Cardoso, JS; Oliveira, SP;

Publicação
NPJ DIGITAL MEDICINE

Abstract
Immunohistochemistry (IHC) is crucial for the clinical categorisation of breast cancer cases. Deep generative models may offer a cost-effective alternative by virtually generating IHC images from hematoxylin and eosin samples. This review explores the state-of-the-art in virtual staining for breast cancer biomarkers (HER2, PgR, ER and Ki-67) and benchmarks several models on public datasets. It serves as a resource for researchers and clinicians interested in applying or developing virtual staining techniques.

2025

Intrinsically-Interpretable Siamese Networks for Identity Recognition

Autores
Rocha, MA; Cardoso, JS; Montenegro, H;

Publicação
2025 IEEE/CVF INTERNATIONAL CONFERENCE ON COMPUTER VISION WORKSHOPS, ICCVW

Abstract
Deep learning models have excelled in computer vision tasks in the past decade, but their lack of transparency raises ethical and legal concerns, especially in high-stakes areas such as surveillance and law enforcement. As such, regulations like the European Union's General Data Protection Regulation are now demanding interpretable Artificial Intelligence systems. This paper focuses on automatic face recognition, where existing systems lack interpretability and research into explainable alternatives is limited. To address this gap, we propose two interpretable facial verification models based on Siamese Networks that match and compare semantically-aligned local regions in the images. Experiments show these models rival and even outperform traditional baselines while offering clearer, more accountable explanations, advancing ethical and legally compliant facial recognition.

2025

GANs vs. Diffusion Models for virtual staining with the HER2match dataset

Autores
Klöckner, P; Teixeira, J; Montezuma, D; Cardoso, JS; Horlings, HM; de Oliveira, SP;

Publicação
CoRR

Abstract

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