For the education of X-ray imaging, having a detailed knowledge on the interaction of radiation with matter is very important. Also the generation and detection concepts of the X-ray have to be grasped well. Sometimes it is not easy to visualize the interactions and assess the scheme in quantum physics level for the medical doctors and the engineers who have not studied on the modern physics in an appropriate level. This thesis aims to visualize these interactions, X-ray generation and detection, and computerized tomographic imaging. With these simulations, the user can 1) observe and analyze which type of interaction occurs under which condition, 2) understand the interaction cross sections and interaction results, 3) visualise X-ray generation and detection features, 4) clarify the method of image reconstruction, and the features affecting the image quality in computerized tomography system. This is accomplished by changing the controllable variables of the radiation and the systems with the provided interfaces. In this thesis, JAVA/FLASH based simulation interfaces are designed to easily assess the subject. The benefits of these software are their ability to execute the programs prepared on the World Wide Web media. The interfaces are accessible from anywhere, at any time.

Made available in DSpace on 2016-06-02T19:58:04Z (GMT). No. of bitstreams: 1 3535.pdf: 15531173 bytes, checksum: 0bec1dee483a9cf070857af8977686a0 (MD5) Previous issue date: 2011-03-18 / Financiadora de Estudos e Projetos / Arborization is fundamental in urban spaces, due to the significant benefits it provides. To important issue to guarantee the adequacy of the role it plays is its maintenance. To this purpose, an application of preventive methods of diagnosis is recommended, allowing the evaluation of external and internal conditions of tress. Currently, the analysis of urban trees is subjectivity. For a complete and secure analysis, it is important to associate this visual external analysis to an internal analysis. This could be done by applying non-destructive techniques, wich allows an internal visualization of the tree through a tomographic image, without causing it any damage. Among the non-destructive techniques, that have applicability in the internal evaluation of urban trees, the technique of stress waves can be highlighted. Considering the great benefits that this technique can provide in the evaluation of urban trees, this research seeks to verify its scientific and technique viability, analyzing its reliability and also establishing some parameters of application. Studies with 12 trees of the Caesalpinea peltophoroides species (popularly known as Sibipiruna) have been carried out. The stress waves equipment was applied to sections of 50, 90 and 130 cm from the trees basis, generating tomographic images of these sections. Afterwards, the trees were cut at the level of these sections and, in order to compare these images, some pictures of them were made. The results show that the trees waves technique presents large applicability for internal evaluation of urban trees, achieving significant results. Also some parameters for the application of this technique were established. For instance, it is necessary to determinate the speed reference of waves propagation for the interpretation of tomographic images, as well as it is to determinate the best height of the assays section. The latter consisting on the height of the diameter to the chest height (DAP), where average density of the tree is representative. / A arborização é fundamental nos espaços urbanos, devido aos importantes benefícios que proporciona. Para garantir que esta exerça adequadamente seu papel, é importante a sua manutenção, na qual é necessário o emprego de métodos de diagnóstico preventivos, que permitam avaliar as condições externas e internas das árvores. Atualmente, a análise de árvores urbanas é realizada basicamente pela análise visual externa, a qual apresenta grande subjetividade. Para uma análise completa e segura é importante que a análise visual externa seja acompanhada de uma análise interna. Esta pode ser realizada por meio de técnicas nãodestrutivas, que possibilitam a visualização interna da árvore através da imagem tomográfica, sem causar nenhum dano a esta. Dentre as técnicas não-destrutivas existentes, com aplicabilidade na avaliação interna de árvores urbanas, pode-se destacar a técnica de ondas de tensão. Diante dos grandes benefícios que esta técnica pode proporcionar na avaliação de árvores urbanas, esta pesquisa buscou verificar sua viabilidade técnica e científica, analisando a sua confiabilidade e estabelecendo parâmetros para sua aplicação. Foram realizados estudos com 12 árvores da espécie Caesalpinea peltophoroides (conhecida popularmente como Sibipiruna), nas quais foram realizadas medições em seções a 50, 90 e 130 cm da base, empregando o equipamento de ondas de tensão, o qual gerou as imagens tomográficas das seções. Em seguida, as árvores foram cortadas nas seções de ensaio e fotografadas, para posterior comparação com a imagem tomográfica gerada. Os resultados permitiram verificar que a técnica de ondas de tensão apresenta grande viabilidade de aplicação na avaliação interna de árvores urbanas, com resultados bastante significativos. Foi possível também estabelecer alguns parâmetros de aplicação da técnica, como a necessidade da determinação da velocidade de propagação da onda de referência, para a interpretação da imagem tomográfica e a determinação da melhor altura da seção para realização dos ensaios, a qual consistiu na altura do diâmetro à altura do peito (DAP), na qual se encontra a representatividade da densidade média da árvore.

La reconstruction tomographique à partir de données de projections est un problème inverse largement utilisé en imagerie médicale et de façon plus modeste pour le contrôle nondestructif. Avec un nombre suffisant de projections, les algorithmes analytiques permettentdes reconstructions rapides et précises. Toutefois, dans le cas d’un faible nombre de vues(imagerie faible dose) et/ou d’angle limité (contraintes spécifiques liées à l’installation), lesdonnées disponibles pour l’inversion ne sont pas complètes, le mauvais conditionnementdu problème s’accentue, et les résultats montrent des artefacts importants. Pour aborderces situations, une approche alternative consiste à discrétiser le problème de reconstruction,et à utiliser des algorithmes itératifs ou une formulation statistique du problème afinde calculer une estimation de l’objet inconnu. Ces méthodes sont classiquement basées surune discrétisation du volume en un ensemble de voxels, et fournissent des cartes 3D de ladensité de l’objet étudié. Les temps de calcul et la ressource mémoire de ces méthodesitératives sont leurs principaux points faibles. Par ailleurs, quelle que soit l’application, lesvolumes sont ensuite segmentés pour une analyse quantitative. Devant le large éventaild’outils de segmentation existant, basés sur différentes interprétations des contours et defonctionnelles à minimiser, les choix sont multiples et les résultats en dépendent.Ce travail de thèse présente une nouvelle approche de reconstruction simultanée àla segmentation des différents matériaux qui composent le volume. Le processus dereconstruction n’est plus basé sur une grille régulière de pixels (resp. voxels), mais sur unmaillage composé de triangles (resp. tétraèdres) non réguliers qui s’adaptent à la formede l’objet. Après une phase d’initialisation, la méthode se décompose en trois étapesprincipales que sont la reconstruction, la segmentation et l’adaptation du maillage, quialternent de façon itérative jusqu’à convergence. Des algorithmes itératifs de reconstructioncommunément utilisés avec une représentation conventionnelle de l’image ont étéadaptés et optimisés pour être exécutés sur des grilles irrégulières composées d’élémentstriangulaires ou tétraédriques. Pour l’étape de segmentation, deux méthodes basées surune approche paramétrique (snake) et l’autre sur une approche géométrique (level set)ont été mises en oeuvre afin de considérer des objets de différentes natures (mono- etmulti- matériaux). L’adaptation du maillage au contenu de l’image estimée est basée surles contours segmentés précédemment, pour affiner la maille au niveau des détails del’objet et la rendre plus grossière dans les zones contenant peu d’information. En finde processus, le résultat est une image classique de reconstruction tomographique enniveaux de gris, mais dont la représentation par un maillage adapté au contenu proposeidirectement une segmentation associée. Les résultats montrent que la partie adaptative dela méthode permet de représenter efficacement les objets et conduit à diminuer drastiquementla mémoire nécessaire au stockage. Dans ce contexte, une version 2D du calcul desopérateurs de reconstruction sur une architecture parallèle type GPU montre la faisabilitédu processus dans son ensemble. Une version optimisée des opérateurs 3D permet descalculs encore plus efficaces. / Tomography reconstruction from projections data is an inverse problem widely used inthe medical imaging field. With sufficiently large number of projections over the requiredangle, the FBP (filtered backprojection) algorithms allow fast and accurate reconstructions.However in the cases of limited views (lose dose imaging) and/or limited angle (specificconstrains of the setup), the data available for inversion are not complete, the problembecomes more ill-conditioned, and the results show significant artifacts. In these situations,an alternative approach of reconstruction, based on a discrete model of the problem,consists in using an iterative algorithm or a statistical modelisation of the problem to computean estimate of the unknown object. These methods are classicaly based on a volumediscretization into a set of voxels and provide 3D maps of densities. Computation time andmemory storage are their main disadvantages. Moreover, whatever the application, thevolumes are segmented for a quantitative analysis. Numerous methods of segmentationwith different interpretations of the contours and various minimized energy functionalare offered, and the results can depend on their use.This thesis presents a novel approach of tomographic reconstruction simultaneouslyto segmentation of the different materials of the object. The process of reconstruction isno more based on a regular grid of pixels (resp. voxel) but on a mesh composed of nonregular triangles (resp. tetraedra) adapted to the shape of the studied object. After aninitialization step, the method runs into three main steps: reconstruction, segmentationand adaptation of the mesh, that iteratively alternate until convergence. Iterative algorithmsof reconstruction used in a conventionnal way have been adapted and optimizedto be performed on irregular grids of triangular or tetraedric elements. For segmentation,two methods, one based on a parametric approach (snake) and the other on a geometricapproach (level set) have been implemented to consider mono and multi materials objects.The adaptation of the mesh to the content of the estimated image is based on the previoussegmented contours that makes the mesh progressively coarse from the edges to thelimits of the domain of reconstruction. At the end of the process, the result is a classicaltomographic image in gray levels, but whose representation by an adaptive mesh toits content provide a correspoonding segmentation. The results show that the methodprovides reliable reconstruction and leads to drastically decrease the memory storage. Inthis context, the operators of projection have been implemented on parallel archituecturecalled GPU. A first 2D version shows the feasability of the full process, and an optimizedversion of the 3D operators provides more efficent compoutations.

Os métodos incrementais pertencem a uma classe de métodos iterativos que divide o conjunto de dados em subconjuntos ordenados, e que atualiza a imagem ao processar cada subconjunto (sub-iterações). Isso acelera a convergência das reconstruções, e imagens de qualidade são obtidas em menos iterações. No entanto, a cada sub-iteração é necessário calcular os operadores de projeção e retroprojeção, resultando no custo computacional de ordem O(n3) para a reconstrução de imagens de dimensão × . Por outro lado, algumas alternativas baseadas na interpolação em uma grade regular no espaço de Fourier ou em transformadas rápidas não-uniformes, dentre outras ideias, foram desenvolvidas a fim de aliviar esse custo computacional. Além disso, diversas abordagens foram bem sucedidas em acelerar o cálculo das iterações de algoritmos clássicos, mas nenhuma havia sido utilizada em conjunto com os métodos incrementais. Neste trabalho é proposta uma nova abordagem em que a técnica de transformada rápida de Fourier não uniforme (NFFT) é utilizada nas sub-iterações de métodos incrementais com o objetivo de efetuar de forma eficiente os cálculos numericamente mais intensos: a projeção e a retroprojeção, resultando em métodos incrementais com complexidade O(n2 log n ). Os métodos propostos são aplicados à tomografia por radiação síncrotron e os resultados da pesquisa mostram um bom desempenho. / Incremental methods belong to a class of iterative methods that divide the data set into ordered subsets, and which update the image when processing each subset (sub-iterations). It accelerates the reconstruction convergence and quality images are obtained in fewer iterations. However, it is necessary to compute the projection and backprojection operators in each sub-iteration, resulting in the computational cost of O(n3) flops for × images. On the other hand, some alternatives based on interpolation over a regular grid on the Fourier space or on nonequispaced fast transforms, among other ideas, were developed in order to alleviate the computational cost. In addition, several approaches substantially speed up the computation of the iterations of classical algorithms, but the incremental methods had not been benefited from these techniques. In this work, a new approach is proposed in which the nonequispaced fast Fourier transform (NFTT) is used in each subiteration of incremental methods in order to perform the numerically intensive calculations efficiently: the projection and backprojection, resulting in incremental methods with complexity O(n2 log n ). The proposed methods are applied to the synchrotron radiation tomography and the results show a good performance.

Alguns trabalhos sobre a resposta do tecido ósseo ao Cianocrilato podem ser encontrados na literatura, embora nenhum deles avalie a resposta histológica e a fixação de enxertos ósseos onlay com o N-Butil-2-Cianocrilato (Indermil™). O objetivo do estudo proposto foi (1) analisar a manutenção do volume de enxertos ósseos onlay fixados à mandíbula de coelhos usando N-Butil-2-Cianocrilato (NB-Cn) ou parafuso de titânio, assim como avaliar (2) a remodelação e incorporação desses enxertos ao leito receptor e também (3) observar a diferença do nível de expressão da proteína tartarato-resistente ácido fosfatase (Trap) envolvida na absorção dos mesmos na presença do NB-Cn e do parafuso de titânio. Dezoito coelhos adultos foram envolvidos nesse estudo. Dois blocos ósseos provenientes da calvária dos coelhos foram transplantados para a mandíbula, em que de um lado do leito receptor o osso autógeno foi fixado com parafuso de osteossíntese (Grupo I - controle), e do outro lado com NB-Cn (Grupo II). Após o procedimento cirúrgico, os animais foram submetidos a exame tomográfico. O sacrifício dos animais ocorreu após 1 (n=9) e 6 (n=9) semanas do procedimento cirúrgico inicial, quando então os animais foram submetidos à nova tomografia. As imagens de tomografia foram usadas para estimativa da manutenção do volume dos enxertos. Cortes histológicos das áreas enxertadas foram preparados para se avaliar o reparo dos enxertos ósseos no sítio receptor e o nível de expressão da proteína Trap. Os resultados tomográficos mostraram melhor manutenção do volume dos enxertos fixados com NB-Cn (p≤0,05) em comparação àqueles fixados com parafuso, em ambos os tempos experimentais. Na avaliação imunohistoquímica, observou-se que a marcação da proteína Trap no período de 6 semanas foi significativamente maior em comparação ao tempo de 1 semana, sem apresentar diferença significante entre os grupos. A análise histológica revelou que embora o NB-Cn tenha provocado a destruição do periósteo, a estabilidade promovida pela cola permitiu que a revascularização e incorporação do enxerto ocorresse de forma semelhante ao grupo controle. Esses resultados indicam que o NB-Cn se comportou de forma superior ao parafuso como material de osteossínte. No entanto, estudos adicionais são necessários para se investigar a toxicidade deste composto quando utilizado como meio de fixação óssea. / Some experimental studies on the bone tissue responses to cyanoacrylate can be found in the literature, although neither evaluating the histological response and the fixation of onlay bone grafts with Indermil™. The aim of the proposed study is (1) to analyze the bone grafts volume maintenance fixed to the mandible of rabbits using Indermil™ or titanium screw, as well as (2) assess the healing of onlay grafts to the recipient bed and (3) the differences of level expression of Trap protein involved in reabsortion of these bone grafts using Indermil™ or an osteosynthesis screw. Eighteen adult New Zealand White rabbits were submitted to calvaria onlay bone grafts on both sides of the mandible. On one side the onlay bone graft were fixated with Indermil™, and on the other side bone graft with an osteosynthesis screw. The wounds were then closed, and a computed tomography was realized immediately after this procedure. The animals were killed after 1 (n=9) and 6 weeks (n=9), then the animals were submitted to another computed tomography (CT). The CT images were used to estimate the bone grafts volume maintenance. Histological sections of the grafted areas were prepared to evaluate the healing of bone grafts in the receptor site and the expression level of Trap protein. The CT scan showed better volume maintenance of the bone grafts fixed with Indermil™ (p≤0.05) compared to those fixed with screws, in both the experimental times. The immunohistochemical evaluation showed that the protein Trap expression in 6-week period was significantly higher compared to the 1-week period, without showing significant difference between the groups. Histological analysis revealed that although the Indermil™ has caused the destruction of the periosteum, the stability provided by the glue allowed that the bone graft revascularization and incorporation has occurred in a similar manner to the control group. These results indicate that the Indermi™ behaved than the screw as osteosynthesys material. However, further studies are needed to investigate the toxicity of this compound when used as a means of bone fixation.

Alguns trabalhos sobre a resposta do tecido ósseo ao Cianocrilato podem ser encontrados na literatura, embora nenhum deles avalie a resposta histológica, micro-tomográfica e biomolecular na fixação de enxertos ósseos onlay com o N-Butil-2-Cianocrilato (IndermilTM). O objetivo do estudo proposto foi comparar o processo de incorporação, remodelação, revascularização e manutenção do volume de enxertos fixados com parafuso ou adesivo, além de mapear os eventos biomoleculares nos quais os enxertos ósseos onlay possam estar envolvidos. Oitenta e oito coelhos adultos foram envolvidos nesse estudo. Dois blocos ósseos provenientes da calvária dos coelhos foram transplantados para a mandíbula, em que de cada lado do leito receptor o osso autógeno foi fixado com parafuso de osteossíntese de forma aposicional, lag screw, cianoacrilato ou parafuso e cianoacrilato. O sacrifício dos animais ocorreu após 3, 7, 20 e 40 dias do procedimento cirúrgico inicial, quando então os animais foram submetidos às análises micro-tomográficas, histológicas e biomoleculares. Cortes histológicos das áreas enxertadas foram preparados para se avaliar o reparo dos enxertos ósseos no sítio receptor. Os resultados biomoleculares mostraram que o método de fixação utilizando o composto N-Butil-2-Cianocrilato (NB-Cn) apresentou um maior potencial anti-inflamatório, revascularizador e de formação óssea, bem como, uma menor reabsorção óssea. Na avaliação histológica, observou-se que embora o NB-Cn tenha impedido a formação de novo osso na área onde foi aplicado, a estabilidade promovida pela cola permitiu que a revascularização e incorporação do enxerto ocorresse de forma semelhante aos demais grupos. Esses resultados indicam que o NB-Cn se comportou de forma semelhante ao parafuso como material de osteossínte. / Some experimental studies on the bone tissue responses to cyanoacrylate can be found in the literature, none of them evaluate the histological response, micro-tomographic and biomolecular on fixation of onlay bone grafts with N-butyl-2-cyanoacrylate (IndermilTM). The aim of the proposed study was to compare the process of incorporation, remodeling, and volume maintenance of grafts set with screw or adhesive and map biomolecular events in which onlay bone grafts may be involved. Eighty-eight adult rabbits were submitted to calvaria onlay bone graft on both sides of the mandible. The grafts were fixated on each side of mandible by a fixation screw appositionally, lag screw, cyanoacrilate or both. The animals were sacrificed on 3rd, 7th, 20th and 40th day after the initial surgical procedure, then they were subjected to micro-computed tomography, histological and biomolecular analysis. Histological sections of the grafted areas were prepared to evaluate the healing of bone grafts in the receptor site. The biomolecular analysis showed that fixation method using N-butyl-2-cyanoacrylate (NB-Cn) presented a greater potential on anti-inflammatory, revascularization and bone formation properties, as well as reduced bone resorption. Histological evaluation observed that although the NB-Cn has prevented the formation of new bone in the area where it was applied, the stability achieved by Nb-Cn allowed revascularization and graft incorporation just like other groups. These results indicate that NB- Cn behaved similarly to the screw as osteosynthesys material.

Near Infrared (NIR) and Photoacoustic (PA) Imaging are promising imaging modalities that provides functional information of the soft biological tissues in-vivo, with applica-tions in breast and brain tissue imaging. These techniques use near infrared light in the wavelength range of (600 nm - 900 nm), giving an advantage of being non-ionizing imaging modality. This makes the prolong bed-side monitoring of tissue feasible, making them highly desirable medical imaging modalities in the clinic. The computation models that are deployed in these imaging scenarios are computationally demanding and often require a high performance computing systems to deploy them in real-time. This the-sis presents three computationally e cient models for near-infrared and photoacoustic imaging, without compromising the quality of measured functional properties, to make them more appealing in clinical scenarios. The attenuation of near-infrared (NIR) light intensity as it propagates in a turbid medium like biological tissue is described by modi ed the BeerLambert law (MBLL). The MBLL is generally used to quantify the changes in tissue chromophore concen-trations for NIR spectroscopic data analysis. Even though MBLL is e ective in terms of providing qualitative comparison, it su ers from its applicability across tissue types and tissue dimensions. A Lambert-W function-based modeling for light propagation in biological tissues is proposed and introduced, which is a generalized version of the Beer-Lambert model. The proposed modeling provides parametrization of tissue properties, which includes two attenuation coe cients o and . The model is validated against the Monte Carlo simulation, which is the gold standard for modeling NIR light propagation in biological tissue. Numerous human and animal tissues are included to validate the proposed empirical model, including an inhomogeneous adult human head model. The proposed model, which has a closed form (analytical), is rst of its kind in providing accurate modeling of NIR light propagation in biological tissues. Model based image reconstruction techniques yield better quantitative accuracy in photoacoustic (PA) image reconstruction, especially in limited data cases. An exponen-tial ltering of singular values is proposed for carrying out the image reconstruction in photoacoustic tomography. The results were compared with widely popular Tikhonov regularization, time reversal, and the state of the art least-squares QR based reconstruc-tion algorithms for three digital phantom cases with varying signal-to-noise ratios of data. The exponential ltering provided superior photoacoustic images of better quanti-tative accuracy. Moreover, the proposed ltering approach was observed to be less biased towards regularization parameter and did not come with any additional computational burden as it was implemented within the Tikhonov ltering framework. It was also shown that the standard Tikhonov ltering becomes an approximation to the proposed exponential ltering. The model based image reconstruction techniques for photoacoustic tomography re-quire an explicit regularization. An error estimate minimization based approach was proposed and developed for the determination of regularization parameter for PA imag-ing. The regularization was used within Lanczos bidiagonalization framework, which provides the advantage of dimensionality reduction for a large system of equations. The proposed method was computationally faster than the state of the art techniques and provided similar performance in terms of quantitative accuracy in reconstructed im-ages.The estimate can also be utilized in determining suitable regularization parameter for other popular techniques such as Tikhonov,exponential ltering and `1 norm based regularization methods.

Les mécanismes d’évolution spatio-temporelle des structures turbulentes instationnaires tridimensionnelles, et en particulier ceux rencontrés aux plus grandes échelles, sont à l’origine de phénomènes d’instabilité qui conduisent très souvent à une diminution de la performance des systèmes énergétiques. C’est le cas des variations cycle-à-cycle dans le moteur à combustion interne. Malgré les progrès substantiels réalisés par la simulation numérique en mécanique des fluides, les approches expérimentales demeurent essentielles pour l’analyse et la compréhension des phénomènes physiques ayant lieu. Dans ce travail de thèse, deux types de vélocimétrie par image de particules (PIV) ont été appliqués et adaptés au banc moteur optique du laboratoire Coria pour étudier l’écoulement en fonction de six conditions de fonctionnement du moteur. La PIV Haute Cadence 2D2C a permis d’abord d’obtenir un suivi temporel de l’écoulement dans le cylindre durant un même cycle moteur ainsi qu’identifier ces variations cycliques. La PIV Tomographique 3D3C a permis ensuite d’étendre les données mesurées vers l’espace tridimensionnel. La Tomo-PIV fait intervenir 4 caméras en position angulaire visualisant un environnement de géométrie complexe, confinée, ayant un accès optique restreint et introduisant des déformations optiques importantes. Cela a nécessité une attention particulière vis-à-vis du processus de calibration 3D des modèles de caméras. Des analyses conditionnées 2D et 3D de l’écoulement sont effectuées en se basant principalement sur la décomposition propre orthogonale (POD) permettant de séparer les différentes échelles de structure et le critère Γ permettant l’identification des centres des tourbillons. / The unsteady evolution of three-dimensional large scale flow structures can often lead to a decrease in the performance of energetic systems. This is the case of cycle-to-cycle variations occurring in the internal combustion engine. Despite the substantial advancement made by numerical simulations in fluid mechanics, experimental measurements remain a requirement to validate any numerical model of a physical process. In this thesis, two types of particle image velocimetry (PIV) were applied and adapted to the optical engine test bench of the Coria laboratory in order to study the in-cylinder flow with respect to six operating conditions. First, the Time-Resolved PIV (2D2C) allowed obtaining a temporal tracking of the in-cylinder flow and identifying cyclic variabilities. Then tomographic PIV (3D3C) allowed extending the measured data to the three-dimensional domain. The Tomo-PIV setup consisted of 4 cameras in angular positioning, visualizing a confined environment with restricted optical access and important optical deformations. This required a particular attention regarding the 3D calibration process of camera models. 2D and 3D conditional analyses of the flow were performed using the proper orthogonal decomposition (POD) allowing to separate the different scales of flow structures and the Γ criterion allowing the identification of vortices centres.

Orientador: Denis Henrique Pinheiro Salvadeo / Resumo: Tomossíntese Mamária Digital (DBT) é uma técnica de imageamento radiográfico, com aquisição de projeções em ângulos limitados utilizando dose reduzida de radiação. Ela tem por objetivo reconstruir fatias tomográficas do interior da mama, possibilitando o diagnóstico precoce de possíveis lesões e aumentando, consequentemente, a probabilidade de cura do paciente. Contudo, devido ao fato de que DBT utiliza doses baixas de radiação, a imagem gerada contém mais ruído que a mamografia digital. Embora a qualidade do exame esteja diretamente relacionada com a dose utilizada, espera-se que a dose de radiação empregada no exame seja a mais baixa possível, mas ainda com qualidade suficiente para que o diagnóstico possa ser realizado, conforme o princípio As Low As Reasonably Achievable (ALARA). Uma das etapas importantes para se buscar o princípio ALARA é a reconstrução tomográfica, que consiste em um software que gera as fatias do interior da mama a partir de um conjunto de projeções 2D de DBT adquiridas. Por outro lado, técnicas de Aprendizado de Máquina, especialmente redes neurais com aprendizado profundo, que recentemente tem evoluído consideravelmente o estado da arte em diversos problemas de Visão Computacional e Processamento de Imagens, tem características adequadas para serem aplicadas também na etapa de reconstrução. Deste modo, este trabalho investigou uma arquitetura básica de rede neural artificial com aprendizado profundo que seja capaz de reconstruir imagens de DBT, espe... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Digital Breast Tomosynthesis (DBT) is a technique of radiographic imaging, with acquisition of projections at limited angles using reduced dose of radiation. It aims to reconstruct tomographic slices inside the breast, making possible the early diagnosis of possible lesions and, consequently, increasing the probability of cure of the patient. However, due to the fact that DBT uses low doses of radiation, the generated image contains more noise than digital mammography. Although the quality of the exam is directly related to the dose applied, the radiation dose used in the examination is expected to be as low as possible, but still keeping enough quality for the diagnosis to be made, as determined by the As Low As Reasonably Achievable (ALARA) principle. One of the important steps to achieve the ALARA principle is the tomographic reconstruction, which consists of a software that generates slices inside the breast from an acquired set of 2D DBT projections. On the other hand, Machine Learning techniques, especially neural networks with deep learning, that have recently evolved considerably the state-of-the-art in several problems in Computer Vision and Image Processing areas, it has suitable characteristics to be applied also in the reconstruction step. Thus, this work investigated a basic architecture of artificial neural network with deep learning that is capable to reconstruct DBT images, especially focused on noise reduction. Furthermore, considering an additional filtering... (Complete abstract click electronic access below) / Mestre

Oscillating-foil hydrokinetic turbines have gained interest over the years to extract energy from renewable sources. The influence of the sweep angle on the performance of a fully-passive oscillating-plate hydrokinetic turbine prototype was investigated experimentally in the present work. The sweep angle was introduced to promote spanwise flow along the plate in order to manipulate the leading edge vortex (LEV) and hydrodynamically optimize the performance of the turbine. In the present work, flat plates of two configurations were considered: a plate with a 6° sweep angle and an unswept plate (control), which were undergoing fully-passive pitch and heave motions in uniform inflow at the Reynolds numbers ranging from 15 000 to 30 000. The resulting kinematic parameters and the energy extraction performance were evaluated for both plates. Planar (2D) particle image velocimetry (PIV) was used to obtain patterns of the phase-averaged out-of-plane vorticity during the oscillation cycle. The circulation in the wake was then related to the induced-forces on the plate by calculating the moments of vorticity of the LEV with respect to the pitching axis of the plate. Tomographic (3D) PIV was implemented in evaluating the influence of the spanwise flow on the dynamics of the vortex structure in three-dimensional space. The rate of deformation of the vortex length was quantified by calculating the deformation terms embedded in the vorticity equations, then linked to the stability of the vortex. The results show evidence of delay of the shedding of LEV and increased vortex stability, in the case of the swept plate. The manipulation of the LEV by the spanwise flow was related to the induced kinematics exhibited by the prolonged heave forces experienced by the swept plate, which led to the higher power extraction performance at high inflow velocities. In the presence of spanwise flow, positive vortex stretching along the vortex line increased the stabilization of the vortex core and prevented the onset of helical vortex breakdown, observed in the case of the unswept plate. The use of the sweep profile on the plate has led to the improvement of energy extraction performance of the fully-passive hydrokinetic turbine. / Graduate