In-plane displacement and strain image analysis

Measurements in civil engineering load tests usually require considerable time and complex procedures. Therefore, measurements are usually constrained by the number of sensors resulting in a restricted monitored area. Image processing analysis is an alternative way that enables the measurement of the complete area of interest with a simple and effective setup. In this article photo sequences taken during load displacement tests were captured by a digital camera and processed with image correlation algorithms. Three different image processing algorithms were used with real images taken from tests using specimens of PVC and Plexiglas. The data obtained from the image processing algorithms were also compared with the data from physical sensors. A complete displacement and strain map were obtained. Results show that the accuracy of the measurements obtained by photogrammetry is equivalent to that from the physical sensors but with much less equipment and fewer setup requirements. © 2015Computer-Aided Civil and Infrastructure Engineering.

A toolbox for hyperspectral image analysis

This paper introduces a new toolbox for hyperspectral imagery, developed under the MATLAB environment. This toolbox provides easy access to different supervised and unsupervised classification methods. This new application is also versatile and fully dynamic since the user can embody their own methods, that can be reused and shared. This toolbox, while extends the potentiality of MATLAB environment, it also provides a user-friendly platform to assess the results of different methodologies. In this paper it is also presented, under the new application, a study of several different supervised and unsupervised classification methods on real hyperspectral data.

Shear-induced lamellar ionic liquid-crystal foam

n a recent paper we reported an experimental study of two N-alkylimidazolium salts. These ionic compounds exhibit liquid crystalline behaviour with melting points above 50 degrees C in bulk. However, if they are sheared, a (possibly non-equilibrium) lamellar phase forms at room temperature. Upon shearing a thin film of the material between microscope slides, textures were observed that are strikingly similar to liquid (wet) foams. The images obtained from polarising optical microscopy (POM) were found to share many of the known quantitative properties of a two-dimensional foam coarsening process. Here we report an experimental study of this foam using a shearing system coupled with POM. The structure and evolution of the foam are investigated through the image analysis of time sequences of micrographs obtained for well-controlled sets of physical parameters (sample thickness, shear rate and temperature). In particular, we find that there is a threshold shear rate below which no foam can form. Above this threshold, a steady-state foam pattern is obtained where the mean cell area generally decreases with increasing shear rate. Furthermore, the steady-state internal cell angles and distribution of the cell number of sides deviate from their equilibrium (i.e. zero-shear) values.

Methods for automatic and assisted image annotation

Personal memories composed of digital pictures are very popular at the moment. To retrieve these media items annotation is required. During the last years, several approaches have been proposed in order to overcome the image annotation problem. This paper presents our proposals to address this problem. Automatic and semi-automatic learning methods for semantic concepts are presented. The automatic method is based on semantic concepts estimated using visual content, context metadata and audio information. The semi-automatic method is based on results provided by a computer game. The paper describes our proposals and presents their evaluations.

Avaliação do desempenho de um sistema híbrido de tomografia por emissão de positrões e tomografia computorizada

Mestrado em Medicina Nuclear.

Dependent component analysis: a hyperspectral unmixing algorithm

Linear unmixing decomposes a hyperspectral image into a collection of reflectance spectra of the materials present in the scene, called endmember signatures, and the corresponding abundance fractions at each pixel in a spatial area of interest. This paper introduces a new unmixing method, called Dependent Component Analysis (DECA), which overcomes the limitations of unmixing methods based on Independent Component Analysis (ICA) and on geometrical properties of hyperspectral data. DECA models the abundance fractions as mixtures of Dirichlet densities, thus enforcing the constraints on abundance fractions imposed by the acquisition process, namely non-negativity and constant sum. The mixing matrix is inferred by a generalized expectation-maximization (GEM) type algorithm. The performance of the method is illustrated using simulated and real data.

Does Independent Component Analysis Play a Role in Unmixing Hyperspectral Data?

Chapter in Book Proceedings with Peer Review First Iberian Conference, IbPRIA 2003, Puerto de Andratx, Mallorca, Spain, JUne 4-6, 2003. Proceedings

Vertex component analysis: a fast algorithm to extract endmembers spectra from hyperspectral data

Chapter in Book Proceedings with Peer Review First Iberian Conference, IbPRIA 2003, Puerto de Andratx, Mallorca, Spain, JUne 4-6, 2003. Proceedings

Variabilidade introduzida pelo operador no processamento dos estudos Gated-SPECT do miocárdio

Introdução – Os estudos Gated – Single Photon Emission Computed Tomography (SPECT) são uma das técnicas de imagiologia cardíaca que mais evoluiu nas últimas décadas. Para a análise das imagens obtidas, a utilização de softwares de quantificação leva a um aumento da reprodutibilidade e exatidão das interpretações. O objetivo deste estudo consiste em avaliar, em estudos Gated-SPECT, a variabilidade intra e interoperador de parâmetros quantitativos de função e perfusão do miocárdio, obtidos com os softwares Quantitative Gated SPECT (QGS) e Quantitative Perfusion SPECT (QPS). Material e métodos – Recorreu-se a uma amostra não probabilística por conveniência de 52 pacientes, que realizaram estudos Gated-SPECT do miocárdio por razões clínicas e que integravam a base de dados da estação de processamento da Xeleris da ESTeSL. Os cinquenta e dois estudos foram divididos em dois grupos distintos: Grupo I (GI) de 17 pacientes com imagens com perfusão do miocárdio normal; Grupo II (GII) de 35 pacientes que apresentavam defeito de perfusão nas imagens Gated-SPECT. Todos os estudos foram processados 5 vezes por 4 operadores independentes (com experiência de 3 anos em Serviços de Medicina Nuclear com casuística média de 15 exames/semana de estudos Gated-SPECT). Para a avaliação da variabilidade intra e interoperador foi utilizado o teste estatístico de Friedman, considerando α=0,01. Resultados e discussão – Para todos os parâmetros avaliados, os respectivos valores de p não traduziram diferenças estatisticamente significativas (p>α). Assim, não foi verificada variabilidade intra ou interoperador significativa no processamento dos estudos Gated-SPECT do miocárdio. Conclusão – Os softwares QGS e QPS são reprodutíveis na quantificação dos parâmetros de função e perfusão avaliados, não existindo variabilidade introduzida pelo operador.

Efeito fisiológico da cafeína em estudos neurológicos com base na ponderação em susceptibilidade ferromagnética (SWI)

Introdução – O presente estudo avaliou o efeito da cafeína no valor da razão contraste ruído (CNR) em imagens SWI. Objetivos – Avaliar o efeito da cafeína qualitativamente e quantificado pelo cálculo do valor CNR em imagens de magnitude e MIP para as estruturas: veia cerebral interna, seio sagital superior, tórcula e artéria cerebral média. Metodologia – A população do estudo incluiu 24 voluntários saudáveis que estiveram pelo menos 24h privados da ingestão de cafeína. Adquiriram-se imagens SWI antes e após a ingestão de 100ml de café. Os voluntários foram subdivididos em quatro grupos de seis indivíduos/grupo e avaliados separadamente após decorrido um intervalo de tempo diferente para cada grupo (15, 25, 30 ou 45min pós-cafeína). Utilizou-se um scanner Siemens Avanto 1,5 T com bobine standard de crânio e os parâmetros: T2* GRE 3D de alta resolução no plano axial, TR=49; TE=40; FA=15; FOV=187x230; matriz=221x320. O processamento de imagem foi efetuado no software OsiriX® e a análise estatística no GraphPadPrism®. Resultados e Discussão – As alterações de sinal e diferenças de contraste predominaram nas estruturas venosas e não foram significantes na substância branca, LCR e artéria cerebral média. Os valores CNR pré-cafeína diferiram significativamente do pós-cafeína nas imagens de magnitude e MIP na veia cerebral interna e nas imagens de magnitude do seio sagital superior e da tórcula (p<0,0001). Não se verificaram diferenças significativas entre os grupos avaliados nos diferentes tempos pós-cafeína. Conclusões – Especulamos que a cafeína possa vir a ser usada como agente de contraste nas imagens SWI barato, eficaz e de fácil administração.

O clima organizacional em unidades hospitalares públicas e privadas: a perspectiva dos técnicos de radiologia

Mestrado em Intervenção Sócio-Organizacional na Saúde. Área de especialização: Políticas de Administração e Gestão de Serviços de Saúde

Cyclic deformation of bidisperse two-dimensional foams

In-plane deformation of foams was studied experimentally by subjecting bidisperse foams to cycles of traction and compression at a prescribed rate. Each foam contained bubbles of two sizes with given area ratio and one of three initial arrangements: sorted perpendicular to the axis of deformation (iso-strain), sorted parallel to the axis of deformation (iso-stress), or randomly mixed. Image analysis was used to measure the characteristics of the foams, including the number of edges separating small from large bubbles N-sl, the perimeter (surface energy), the distribution of the number of sides of the bubbles, and the topological disorder mu(2)(N). Foams that were initially mixed were found to remain mixed after the deformation. The response of sorted foams, however, depended on the initial geometry, including the area fraction of small bubbles and the total number of bubbles. For a given experiment we found that (i) the perimeter of a sorted foam varied little; (ii) each foam tended towards a mixed state, measured through the saturation of N-sl; and (iii) the topological disorder mu(2)(N) increased up to an "equilibrium" value. The results of different experiments showed that (i) the change in disorder, Delta mu(2)(N), decreased with the area fraction of small bubbles under iso-strain, but was independent of it under iso-stress; and (ii) Delta mu(2)(N) increased with Delta N-sl under iso-strain, but was again independent of it under iso-stress. We offer explanations for these effects in terms of elementary topological processes induced by the deformations that occur at the bubble scale.

Study and comparison of physiological response with Harmony® suspension system and suspension with pin

The purpose of this study is a cross-qualitative and quantitative gait analysis in 3 traumatic unilateral amputees using prosthesis with pin suspension compared to the use of prosthesis with a high vacuum suspension, the Harmony® system. In Portugal, there aren’t many studies made in the field of orthotic and prosthetic and knowledge about the number of amputees in the country. The only know is that the major cause of lower limb amputation is diabetes mellitus, being the most affected population the older age groups. The combination of technological developments with daily needs of the amputees is becoming more and more important for they better quality of life. This work was done during the curricular unit “Investigation in Prosthetics and Orthotics” class, in the 4th year of Health Technology School of Lisbon, in Portugal. This study analyzes if the change of suspension in transtibial prosthesis will influence some physiological response in amputees.

Integrated vehicle classification system

This paper presents an integrated system for vehicle classification. This system aims to classify vehicles using different approaches: 1) based on the height of the first axle and_the number of axles; 2) based on volumetric measurements and; 3) based on features extracted from the captured image of the vehicle. The system uses a laser sensor for measurements and a set of image analysis algorithms to compute some visual features. By combining different classification methods, it is shown that the system improves its accuracy and robustness, enabling its usage in more difficult environments satisfying the proposed requirements established by the Portuguese motorway contractor BRISA.

Avaliação ecocardiográfica da função sistólica ventricular direita em doentes com disfunção ventricular esquerda: parâmetros convencionais versus strain bidimensional

Mestrado em Tecnologia de Diagnóstico e Intervenção Cardiovascular.