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Publications

Publications by Aurélio Campilho

2004

Automatic lane and band detection in images of thin layer chromatography

Authors
Sousa, AV; Aguiar, R; Mendonca, AM; Campilho, A;

Publication
IMAGE ANALYSIS AND RECOGNITION, PT 2, PROCEEDINGS

Abstract
This work aims at developing an automatic method for the analysis of TLC images for measuring a set of features that can be used for the characterization of the distinctive patterns that result from the separation of oligosaccharides contained in human urine. This paper describes the methods developed for the automatic detection of the lanes contained in TLC images, and for the automatic separation of bands for each detected lane. The extraction of quantitative information related with each band was accomplished with two methods: the EM expectation-maximization and nonlinear least squares trust-region algorithms. The results of these methods, as well as additional quantitative information related with each band, are also presented.

2004

Detection of rib borders on X-ray chest radiographs

Authors
Moreira, R; Mendonca, AM; Campilho, A;

Publication
IMAGE ANALYSIS AND RECOGNITION, PT 2, PROCEEDINGS

Abstract
The purpose of the research herein presented is the automatic detection of the rib borders in posterior-anterior (PA) digital chest radiographs. In a computer-aided diagnosis system, the precise location of the ribs is important as it allows reducing the false positive in the detection of abnormalities such as nodules, rib lesions and lung lesions. We adopted an edge based approach aiming at detecting the lower border of each rib. For this purpose, the rib geometric model is described as a parabola. For each rib, the upper limit is obtained using the position of the corresponding lower border.

2004

Bounds for the average generalization error of the mixture of experts neural network

Authors
Alexandre, LA; Campilho, A; Kamel, M;

Publication
STRUCTURAL, SYNTACTIC, AND STATISTICAL PATTERN RECOGNITION, PROCEEDINGS

Abstract
In this paper we derive an upper bound for the average-case generalization error of the mixture of experts modular neural network, based on an average-case generalization error bound for an isolated neural network. By doing this we also generalize a previous bound for this architecture that was restricted to special problems. We also present a correction factor for the original average generalization error, that was empirically obtained, that yields more accurate error bounds for the 6 data sets used in the experiments. These experiments illustrate the validity of the derived error bound for the mixture of experts modular neural network and show how it can be used in practice.

2006

Lung parenchyma segmentation from CT images based on material decomposition

Authors
Vinhais, C; Campilho, A;

Publication
IMAGE ANALYSIS AND RECOGNITION, PT 2

Abstract
We present a fully automated method for extracting the lung region from volumetric X-ray CT images based on material decomposition. By modeling the human thorax as a composition of different materials, the proposed method follows a threshold-based, hierarchical voxel classification strategy. The segmentation procedure involves the automatic computation of threshold values and consists on three main steps: patient segmentation and decomposition, large airways extraction and lung parenchyma decomposition, and lung region of interest segmentation. Experimental results were performed on thoracic. CT images acquired from 30 patients. The method provides a reproducible set of thresholds for accurate extraction of the lung parenchyma, needed for computer aided diagnosis systems.

2006

A multiclassifier approach for lung nodule classification

Authors
Pereira, CS; Alexandre, LA; Mendonca, AM; Campilho, A;

Publication
IMAGE ANALYSIS AND RECOGNITION, PT 2

Abstract
The aim of this paper is to examine a multiclassifier approach to the classification of the lung nodules in X-ray chest radiographs. The approach investigated here is based on an image region-based classification whose output is the information of the presence or absence of a nodule in an image region. The classification was made, essentially, in two steps: firstly, a set of rotation invariant features was extracted from the responses of a multi-scale and multi-orientation filter bank; secondly, different classifiers (multi-layer perceptrons) are designed using different features sets and trained in different data. These classifiers are further combined in order to improve the classification performance. The obtained results are promising and can be used for reducing the false-positives nodules detected in a computer-aided diagnosis system.

2006

The class imbalance problem in TLC image classification

Authors
Sousa, AV; Mendonca, AM; Campilho, A;

Publication
IMAGE ANALYSIS AND RECOGNITION, PT 2

Abstract
The paper presents the methodology developed to solve the class imbalanced problem that occurs in the classification of Thin-Layer Chromatography (TLC) images. The proposed methodology is based on resampling, and consists in the undersampling of the majority class (normal class), while the minority classes, which contain Lysosomal Storage Disorders (LSD) samples, are oversampled with the generation of synthetic samples. For image classification two approaches are presented, one based on a hierarchical classifier and another uses a multiclassifier system, where both classifiers are trained and tested using balanced data sets. The results demonstrate a better performance of the multiclassifier system using the balanced sets.

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