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Publications

Publications by Ana Maria Mendonça

2008

Chromatographic pattern classification

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

Publication
IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING

Abstract
In this paper, we propose and evaluate methodologies for the classification of images from thin-layer chromatography. Each individual sample is characterized by an intensity profile that is further represented into a feature space. The first steps of this process aim at obtaining a robust estimate of the intensity profile by filtering noise, reducing the influence of background changes, and by fitting a mixture of Gaussians. The resulting profiles are represented by a set of appropriate features trying to characterize the state of nature, here spread out over four classes, one for normal subjects and the other three corresponding to lysosomal diseases, which are disorders responsible for severe nerve degeneration. For classification purposes, a novel solution based on a hierarchical structure is proposed. The main conclusion of this paper is that an automatically generated decision tree presents better results than more conventional solutions, being able to deal with the natural imbalance of the data that, as consequence of the rarity of lysosomal disorders, has very few representative cases in the disease classes when compared with the normal population.

2008

Automatic cell segmentation from confocal microscopy images of the Arabidopsis root

Authors
Marcuzzo, M; Quelhas, P; Campilho, A; Mendonca, AM; Campilho, A;

Publication
2008 IEEE INTERNATIONAL SYMPOSIUM ON BIOMEDICAL IMAGING: FROM NANO TO MACRO, VOLS 1-4

Abstract
In vivo observation and tracking of cell division in the Arabidopsis thaliana root meristem, by time-lapse confocal microscopy, is central to biology research. The research herein described is based on large amount of image data, which must be analyzed to determine the location and state of cells. The possibility of automating the process of cell detection/marking is an important step to provide research tools to the biologists in order to ease the search for a special event as cell division. This paper discusses an automatic cell segmentation method, which selects the best cell candidates from a starting watershed based image segmentation. The selection of individual cells is obtained using a Support Vector Machine (SVM) classifier, based on the shape and edge strength of the cells' contour. The resulting segmentation is largely pruned of badly segmented cells, which can reduce the false positive detection of cell division. This is a good result on its own and a starting point for improvement of cell segmentation methodology.

2010

3D cell nuclei fluorescence quantification using sliding band filter

Authors
Quelhas, P; Mendonca, AM; Campilho, A;

Publication
Proceedings - International Conference on Pattern Recognition

Abstract
Plant development is orchestrated by transcription factors whose expression has become observable in living plants through the use of fluorescence microscopy. However, the exact quantification of expression levels is still not solved and most analysis is only performed through visual inspection. With the objective of automating the quantification of cell nuclei fluorescence we present a new approach to detect cell nuclei in 3D fluorescence confocal microscopy, based on the use of the sliding band convergence filter (SBF). The SBF filter detects cell nuclei and estimate their shape with high accuracy in each 2D image plane. For 3D detection, individual 2D shapes are joined into 3D estimates and then corrected based on the analysis of the fluorescence profile. The final nuclei detection's precision/recall are of 0.779/0.803 respectively, and the average Dice's coefficient of 0.773. © 2010 IEEE.

1999

Automatic segmentation of microaneurysms in retinal angiograms of diabetic patients

Authors
Mendonca, AM; Campilho, AJ; Nunes, JM;

Publication
Proceedings - International Conference on Image Analysis and Processing, ICIAP 1999

Abstract
In this paper a method for automatic detection of microaneurysms in digital angiograms of the eye fundus is described. These lesions of the human retina, a characteristic of the earliest phases of diabetic retinopathy, present themselves in the angiographic images as small, round, hyperfluorescent objects. The proposed method includes initial pre-processing and enhancement steps, followed by object segmentation. In the final phase, microaneurysms are validated using two new criteria based on local intensity, contrast and shape relations. The combination of these local features with global image parameters makes possible a high degree of independence from image intensity characteristics. © 1999 IEEE.

2009

Automated Arabidopsis plant root cell segmentation based on SVM classification and region merging

Authors
Marcuzzo, M; Quelhas, P; Campilho, A; Mendonca, AM; Campilho, A;

Publication
COMPUTERS IN BIOLOGY AND MEDICINE

Abstract
To obtain development information of individual plant cells, it is necessary to perform in vivo imaging of the specimen under study, through time-lapse confocal microscopy. Automation of cell detection/marking process is important to provide research tools in order to ease the search for special events, such as cell division. In this paper we discuss an automatic cell detection approach for Arabidopsis thaliana based on segmentation, which selects the best cell candidates from a starting watershed-based image segmentation and improves the result by merging adjacent regions. The selection of individual cells is obtained using a support vector machine (SVM) classifier, based on a cell descriptor constructed from the shape and edge strength of the cells' contour. In addition we proposed a novel cell merging criterion based on edge strength along the line that connects adjacent cells' centroids, which is a valuable tool in the reduction of cell over-segmentation. The result is largely pruned of badly segmented and over-segmented cells, thus facilitating the study of cells. When comparing the results after merging with the basic watershed segmentation, we obtain 1.5% better coverage (increase in F-measure) and up to 27% better precision in correct cell segmentation.

2008

Dissimilarity-based classification of chromatographic profiles

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

Publication
PATTERN ANALYSIS AND APPLICATIONS

Abstract
This paper proposes a non-parametric method for the classification of thin-layer chromatographic (TLC) images from patterns represented in a dissimilarity space. Each pattern corresponds to a mixture of Gaussian approximation of the intensity profile. The methodology comprises various phases, including image processing and analysis steps to extract the chromatographic profiles and a classification phase to discriminate among two groups, one corresponding to normal cases and the other to three pathological classes. We present an extensive study of several dissimilarity-based approaches analysing the influence of the dissimilarity measure and the prototype selection method on the classification performance. The main conclusions of this paper are that, Match and Profile-difference dissimilarity measures present better results, and a new prototype selection methodology achieves a performance similar or even better than conventional methods. Furthermore, we also concluded that simplest classifiers, such as k-NN and linear discriminant classifiers (LDCs), present good performance being the overall classification error less than 10% for the four-class problem.

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