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Publications

Publications by Ana Maria Mendonça

2001

A neural network approach for the automatic detection of microaneurysms in retinal angiograms

Authors
Kamel, M; Belkassim, S; Mendonca, AM; Campilho, A;

Publication
IJCNN'01: INTERNATIONAL JOINT CONFERENCE ON NEURAL NETWORKS, VOLS 1-4, PROCEEDINGS

Abstract
In this paper a neural network structure is used to develop a system capable of detecting microaneurysms locations in retinal angiograms. The LVQ (learning vector quantization) neural network is used to classify the input patterns into their desired classes using competitive layers. The neurons in the competitive layers compete among each other to produce subclasses. These subclasses are then combined to produce the desired output classes. The input vector of the neural network is derived from a grid of smaller image windows. The presence of microaneurysms in these windows is detected according to a novel multi-stage training procedure that has proved to be very effective.

2007

Evaluation of contrast enhancement filters for lung nodule detection

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

Publication
IMAGE ANALYSIS AND RECOGNITION, PROCEEDINGS

Abstract
The aim of this paper is to evaluate and compare the performance of three convergence index (CI) filters when applied to the enhancement of chest radiographs, aiming at the detection of lung nodules. One of these filters, the sliding band filter (SBF), is the proposal of an innovative operator, while the other two CI class members, the iris filter (IF) and the adaptive ring filter (ARF), are already known in this application. To demonstrate the adequacy of the new filter for the enhancement of chest x-ray images, we calculated several figures of merit with the goal of comparing (i) the contrast enhancement capability of the filters, and (ii) the behavior of the filters for the detection of lung nodules. The results obtained for 154 images with nodules of the JSRT database show that the SBF outperforms both the IF and ARF. The proposed filter demonstrated to be a promising enhancement method, thus justifying its use in the first stage of a computer-aided diagnosis system for the detection of lung nodules.

2007

Detection of lung nodule candidates in chest radiographs

Authors
Pereira, CS; Fernandes, H; Mendonca, AM; Campilho, A;

Publication
Pattern Recognition and Image Analysis, Pt 2, Proceedings

Abstract
This paper presents an automated method for the selection of a set of lung nodule candidates, which is the first stage of a computer-aided diagnosis system for the detection of pulmonary nodules. An innovative operator, called sliding band filter (SBF), is used for enhancing the lung field areas. In order to reduce the influence of the blood vessels near the mediastinum, this filtered image is multiplied by a mask that assigns to each lung field point an a priori probability of belonging to a nodule. The result is further processed with a watershed segmentation method that divides each lung field into a set of non-overlapping areas. Suspicious nodule locations are associated with the regions containing the highest regional maximum values. The proposed method, whose result is an ordered set of lung nodule candidate regions, was evaluated on the 247 images of the JSRT database with very promising results.

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.

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.

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