Made available in DSpace on 2014-06-11T19:22:55Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-03-22Bitstream added on 2014-06-13T20:29:21Z : No. of bitstreams: 1 carbi_edo_me_botib.pdf: 472322 bytes, checksum: 8ecb5a0fd41e4de777f29c5cabf5f9ce (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A tarefa preliminar para a construção de um fantoma é a quantificação das espessuras médias de tecidos biológicos presentes na região de interesse. Para atingir esse objetivo, foi desenvolvido um algoritmo computacional capaz de classificar e quantificar os tecidos biológicos, obtidos a partir de imagens tomográficas. O algoritmo desenvolvido ainda converte as espessuras médias de tecidos biológicos (moles, adiposos e ósseos) em respectivas espessuras de materiais simuladores (polimetilmetacrilato e alumínio). A validação do método foi realizada, comparativamente, entre as espessuras de tecidos presentes no tórax de um fantoma antropomórfico (RANDO), pacientes adultos e materiais simuladores de um fantoma homogêneo (FEP). O processo de validação mostrou resultados satisfatórios para os tecidos avaliados, apresentando o maior desvio para o tecido ósseo do adulto padrão (em tomo de 18,80%) quando comparado ao RA DO. Uma vez validado o método, este foi aplicado em imagens tomográficas pediátricas do tórax de pacientes de O a 1 ano de vida. O resultado desta pesquisa mostrou que um único fantoma pode representar todas as faixas de DAPs pediátricas (8,5 - 13,0)cm, avaliadas neste estudo. O fantoma desenvolvido foi calibrado para tensões normalmente utilizadas, na realização de exames de tórax pediátricos (55, 60, 65 e 70)kVp, a partir de curvas sensitométricas. Essas curvas foram utilizadas para quantificação de parâmetros fisicos, que influenciam na qualidade final da imagem. O resultado dessa avaliação mostrou que as curvas apresentam compOliamentos similares, diferindo somente em quantidade de exposição para produção de Densidades Óticas (DO) desejáveis. O resultado desta pesquisa provê contribuições ongmals quanto ao desenvolvimento e construção de fantoma pediátrico, contribuindo com a menor relação risco-beneficio para o paciente pediátrico / The first task to phantom construction is to quantify the average thickness of biological tissue in the region of interesting. To reach this aim, we have developed one compLltedalgoritlun that makes possible to classify and quantify the biological tissues gotten from tomographic images. The algoritlun developed stilI convert the average thickness of biological tissues (soft, fat and bone) in the respective thickness of simulator materiaIs (polymethylmethacrylate and aluminum). The validation of method was carried tlu'ough by companson between the thickness of tissues present in the thorax of anthropomorphic phantom (RA DO), standard adult and simulator materiaIs of the homogeneous phantom (PEP). The process of validation showed satisfactory results for tissues evaluated. The biggest deviation for bone tissue, belongs to standard adult, was around of 18.80%, when compared to RANOO. After the validation method, it was applied to pediatric tomographic images of thorax for patients who are O to 1 years old. The results of this research showed that one phantom can represent alI pediatric OAP bands (8,5 - 13,0) cm, evaluated in this study. The phantom developed was calibrated for voltages general1y used in the accomplishment of pediatric thorax examinations (55, 60, 65 and 70) kVp, from sensitometric curves. These curves had been used for quantification of physical parameters, which has intluence in the quality of images. The result of this evaluation showed that this curves present the same behaviors. The difference is only in the amoLlntof exposition, which is capable to produce the Optical Oensity (DO) desirable. The results of this research provide original contributions for the process of development and construction of pediatric phantom. ln additional this research contributes with the smalIest risk-benefit relationship to pediatric patient

Orientador: José Ricardo de Arruda Miranda / Coorientador: Diana Rodrigues de Pina / Banca: Sérgio José Barbosa Duarte / Banca: Tânia Aparecida Correia Furquim / Resumo: A tarefa preliminar para a construção de um fantoma é a quantificação das espessuras médias de tecidos biológicos presentes na região de interesse. Para atingir esse objetivo, foi desenvolvido um algoritmo computacional capaz de classificar e quantificar os tecidos biológicos, obtidos a partir de imagens tomográficas. O algoritmo desenvolvido ainda converte as espessuras médias de tecidos biológicos (moles, adiposos e ósseos) em respectivas espessuras de materiais simuladores (polimetilmetacrilato e alumínio). A validação do método foi realizada, comparativamente, entre as espessuras de tecidos presentes no tórax de um fantoma antropomórfico (RANDO), pacientes adultos e materiais simuladores de um fantoma homogêneo (FEP). O processo de validação mostrou resultados satisfatórios para os tecidos avaliados, apresentando o maior desvio para o tecido ósseo do adulto padrão (em tomo de 18,80%) quando comparado ao RA DO. Uma vez validado o método, este foi aplicado em imagens tomográficas pediátricas do tórax de pacientes de O a 1 ano de vida. O resultado desta pesquisa mostrou que um único fantoma pode representar todas as faixas de DAPs pediátricas (8,5 - 13,0)cm, avaliadas neste estudo. O fantoma desenvolvido foi calibrado para tensões normalmente utilizadas, na realização de exames de tórax pediátricos (55, 60, 65 e 70)kVp, a partir de curvas sensitométricas. Essas curvas foram utilizadas para quantificação de parâmetros fisicos, que influenciam na qualidade final da imagem. O resultado dessa avaliação mostrou que as curvas apresentam compOliamentos "similares", diferindo somente em quantidade de exposição para produção de Densidades Óticas (DO) desejáveis. O resultado desta pesquisa provê contribuições ongmals quanto ao desenvolvimento e construção de fantoma pediátrico, contribuindo com a menor relação risco-beneficio para o paciente pediátrico / Abstract: The first task to phantom construction is to quantify the average thickness of biological tissue in the region of interesting. To reach this aim, we have developed one compLltedalgoritlun that makes possible to classify and quantify the biological tissues gotten from tomographic images. The algoritlun developed stilI convert the average thickness of biological tissues (soft, fat and bone) in the respective thickness of simulator materiaIs (polymethylmethacrylate and aluminum). The validation of method was carried tlu'ough by companson between the thickness of tissues present in the thorax of anthropomorphic phantom (RA DO), standard adult and simulator materiaIs of the homogeneous phantom (PEP). The process of validation showed satisfactory results for tissues evaluated. The biggest deviation for bone tissue, belongs to standard adult, was around of 18.80%, when compared to RANOO. After the validation method, it was applied to pediatric tomographic images of thorax for patients who are O to 1 years old. The results of this research showed that one phantom can represent alI pediatric OAP bands (8,5 - 13,0) cm, evaluated in this study. The phantom developed was calibrated for voltages general1y used in the accomplishment of pediatric thorax examinations (55, 60, 65 and 70) kVp, from sensitometric curves. These curves had been used for quantification of physical parameters, which has intluence in the quality of images. The result of this evaluation showed that this curves present the same behaviors. The difference is only in the amoLlntof exposition, which is capable to produce the Optical Oensity (DO) desirable. The results of this research provide original contributions for the process of development and construction of pediatric phantom. ln additional this research contributes with the smalIest risk-benefit relationship to pediatric patient / Mestre

The underlying opportunity for this study is that process materials may show considerable change in their electrical properties in response to an injected signal over a wide frequency range. The use of this concept to demonstrate the construction of tomographic images for a range of frequency bands is described. These can then provide a deeper understanding and interpretation of a process under investigation. The thesis presents an in-depth review of the characteristics of the various wideband signals that could be used for simultaneous spectral measurements. This includes an objective selection process that demonstrates that a Chirp signal form offers key advantages. It then addresses the details of the developed method and algorithms for WElT systems that deploy a Chirp wideband excitation signal and a further aspect of the method, based on the time-frequency analysis, particularly wavelet transform, which is used to reveal spectral data sets. The method has been verified by simulation studies which are described. To provide measurements over a required frequency range a linear chirp is deployed as the excitation signal and corresponding peripheral measurements are synthesised using a 2D model. The measurements are then analysed using a wavelet transform algorithm to reveal spectral datasets which are exemplified in the thesis. The thesis then examines the feasibility of the presented method through various experimental trials; an overview of the implementation of the electronic system is included. This provides a single-channel EIT chirp excitation implementation, in essence simulating a real-time parallel data collection system. through the use of pseudo-static tests on foodstuff materials. The experimental data were then analysed and tomographic images reconstructed using the frequency banded data. These included results illustrate the promise of this composite approach in exploiting sensitivity to variations over a wide frequency range. They indicate that the described method can augment an EIT sensing procedure to support spectroscopic analysis of the process materials.

We investigate experimentally the turbulent flow through a two-dimensional contraction. Using a water tunnel with an active grid we generate turbulence at Taylor microscale Reynolds number Reλ ~ 250 which is advected through a 2.5:1 contraction. Volumetric and time-resolved Tomo-PIV and Shake-The-Box velocity measurements are used to characterize the evolution of coherent vortical structures at three streamwise locations upstream of, and within the contraction. We confirm the conceptual picture of coherent large-scale vortices being stretched and aligned with the mean rate of strain. This alignment of the vortices with the tunnel centerline is stronger compared to the alignment of vorticity with the large-scale strain observed in numerical simulations of homogeneous turbulence. We judge this by the peak probability magnitudes of these alignments. This result is robust and independent of the grid-rotation protocols. On the other hand, while the point-wise vorticity vector also, to a lesser extent, aligns with the mean strain, it principally remains aligned with the intermediate eigen-vector of the local instantaneous strain-rate tensor, as is known in other turbulent flows. These results persist when the distance from the grid to the entrance of the contraction is doubled, showing that modest transverse inhomogeneities do not significantly affect these vortical-orientation results.

Sedimentary rock-hosted deposits are a major source of copper and cobalt, with the Neoproterozoic central African Copperbelt being among the largest Cu-Co provinces in the world, accounting for around 15% of its copper resource. The deposits occur primarily in the carbonates and siliciclastic sediments overlying the basement, and formed during early diagenesis (around 820 Ma) and late diagenesis/metamorphism during the Pan-African Orogeny (580-520 Ma). The northwest province of Zambia hosts three major copper deposits, amongst which is Kansanshi: the focus of this study. The deposit, which lies north of the Solwezi dome, is hosted within the Katangan Supergroup, particularly within the carbonaceous phyllites and porphyroblastic schists of the Mshwaya subgroup and lower Nguba Group and extends along the strike length of the North-West trending Kansanshi antiform. In this study, tomographic inversion is applied to first arrival refraction data collected at the Kansanshi Copper Mine with the aim of locating potential copper-bearing structures.  The survey was carried out using both dynamite and VIBSIST sources along 3 profiles; 2 trending North-East across the Kansanshi anticline and 1 trending north-west parallel to it. Seismic refraction tomography is an excellent tool for investigating the shallow subsurface, providing a velocity distribution. Unlike conventional refraction seismics, it allows for the velocity calculation of each cell in a non-homogeneous earth model, rather than just the average velocity of individual layers - allowing us to map structure and infer geological units and weathering profiles. The data highlights abundant faulting and varying depth to fresh bedrock. The various lithologies have also been interpreted.

Mathematical models are used to estimate physiological parameters which are otherwise inaccessible to measurement. When applied to tracer kinetic data obtained in positron tomographic studies, these methods allow for the quantitative analysis of regional metabolic rates in the human brain during life. Dopamine, a neurotransmitter in the mammalian central nervous system, is synthesized by the action of aromatic amino acid decarboxylase on L-dihydroxyphenylalanine (L-dopa). A fluorinated analogue of L-dopa, 6-[18F]fluoro-L-dopa, is used as a tracer in positron tomography to study the nigrostriatal dopaminergic system. Although this tracer has been in use in man for over ten years, a definitive method of quantitative analysis has not yet emerged. The comparison of quantitative results obtained by this approach has been confounded by the diversity of mathematical modelling techniques employed. These techniques range from simple graphical analyses, which yield a single rate constant for the entire system, to complex compartmental approaches, which may not present a unique solution. The goal of this research has been to develop an approach to quantitative analysis which is both informative and mathematically justifiable. Compartmental models of increasing complexity have been evaluated by statistical methods (F-test) to determine the simplest model which adequately fits the data. This strict methodological approach indicates that a two-compartment, three-parameter model produces the best fit, in a statistical sense, to the measured data. This data has also been analyzed by a simple graphical method to yield an influx constant for the system. The influx constant has also been calculated, for comparison, from the results of the compartmental analysis. The two methods were found to be in excellent agreement; both responded predictably to physiological perturbations of the system. While the compartmental method yielded a more informative analysis of the system, the graphically determined influx constant was found to be less sensitive to measurement errors. It is recommended that these two methods be applied in parallel, such that the comparison of results may serve as an internal measure of the integrity of the analysis. / Thesis / Master of Science (MS)

No description available.

International Telemetering Conference Proceedings / October 22-25, 2001 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Synthetic-aperture microwave imaging with ground penetrating radar systems has become a research topic of great importance for the potential applications in sensing and profiling of civil and geophysical structures. It allows us to visualize subsurface structures for nondestructive evaluation with microwave tomographic images. This paper provides an overview of the research program, ranging from the formation of the concepts, physical and mathematical modeling, formulation and development of the image reconstruction algorithms, laboratory experiments, and full-scale field tests.

In this dissertation, imaging characteristics of a nano-slit are investigated. Applications of a scanning and rotating nano-slit in measuring sub-micron aerial features are demonstrated. Coherent sub-micron spot distributions are reconstructed with a very high contrast. Finally, high NA partially coherent images with features as small as 210 nm half-pitch are reconstructed and the ultimate resolution of the system is determined.A nano-slit is characterized as a sensor for coherent line-and-space features. Experiments and simulation verify image detection with contrasts greater than 0.9. Effects of polarization on imaging performance are reported. A scanning and rotating nano-slit in conjunction with a filtered back-projection technique is used to reconstruct sub-micron coherent spot distributions. Simulation results show very good agreement with the experiment. Further, it is shown that the reconstruction is very resilient to some common random experimental errors.Imaging characteristics of a scanning nano-slit sensor are determined for high NA partially coherent images. Good imaging performance (contrast > 0.8) is demonstrated with line-and-space images up to a spatial frequency of 2.38 lp / micron. Sub-micron features in a high NA partially coherent image are measured with a scanning and rotating nano-slit. A modified microscope is used to create the measured features, including 210 nm half-pitch features that cannot be imaged using the microscope in a conventional imaging mode. Using the filtered back projection technique, two-dimensional sub-micron features are reconstructed by the nano-slit sensor. It is determined that the resolution limit of ~ 200 nm is determined by the reconstruction technique and not by the width of the nano-slit.

La pratique clinique a été profondément transformée par l'explosion technologique, ces dernières décades, des techniques d'imagerie médicale. L'expansion de la radiologie interventionnelle a ainsi rendu possible des procédures dites « minimalement invasives » au cours desquelles la thérapie est délivrée directement au niveau de la région pathologique via des micro-outils guidés par imagerie à travers le système vasculaire. Des systèmes dits « C-arm », générant une imagerie rayons X planaire temps-réelle en faible dose, sont utilisés pour le guidage. Ils ont offert plus récemment la possibilité d'une visualisation tridimensionnelle par le biais d'acquisitions tomographiques. C'est dans ce contexte de reconstruction tomographique que s'inscrivent ces travaux de thèse. Ils s'attèlent en particulier à corriger les artefacts de mouvement dus aux variations temporelles des vaisseaux injectés et se concentrent sur un aspect central de la tomographie, à savoir l'échantillonnage angulaire. La théorie du compressed sensing identifie les conditions sous lesquelles des données sous-échantillonnées peuvent être reconstruites en minimisant une fonctionnelle qui combine un terme de fidélité quadratique et une contrainte parcimonieuse. S'appuyant sur cette théorie, un formalisme original de reconstruction est proposé : il repose sur la rétroprojection filtrée itérative, les algorithmes proximaux, la minimisation de normes L1 et l'homotopie. Ce formalisme est ensuite dérivé pour intégrer différentes contraintes spatiales et temporelles. Une telle stratégie s'avère plus performante que la rétroprojection filtrée analytique utilisée dans la pratique clinique, permettant la réduction d'artefacts de mouvement et d'échantillonnage dans des cas cliniques bien identifiés de l'imagerie cérébrale et abdominale. Les résultats obtenus soulignent l'une des principales contributions de ce travail, à savoir : l'importance de l'homotopie, en supplément de la régularisation, pour améliorer la qualité image, un gain indispensable dans le domaine d'applicabilité / Medical imaging has known great advances over the past decades to become a powerful tool for the clinical practice. It has led to the tremendous growth of interventional radiology, in which medical devices are inserted and manipulated under image guidance through the vascular system to the pathology location and then used to deliver the therapy. In these minimally-invasive procedures, X-ray guidance is carried out with C-arm systems through two-dimensional real-time projective low-dose images. More recently, three-dimensional visualization via tomographic acquisition has also become available. This work tackles tomographic reconstruction in the aforementioned context. More specifically, it deals with the correction of motion artifacts that originate from the temporal variations of the contrast-enhanced vessels and thus tackles a central aspect of tomography: data (angular) sampling. The compressed sensing theory identifies conditions under which subsampled data can be recovered through the minimization of a least-square data fidelity term combined with sparse constraints. Relying on this theory, an original reconstruction framework is proposed based on iterative filtered backprojection, proximal splitting, `1-minimization and homotopy. This framework is derived for integrating several spatial and temporal penalties. Such a strategy is shown to outperform the analytical filtered backprojection algorithm that is used in the current clinical practice by reducing motion and sampling artifacts in well-identified clinical cases, with focus on cerebral and abdominal imaging. The obtained results emphasize one of the key contributions of this work that is the importance of homotopy in addition to regularization, to provide much needed image quality improvement in the suggested domain of applicability.