A characteristic feature of Chronic Obstructive Pulmonary Disease (COPD) is an abnormal inflammatory response in the lungs to inhaled particles or gases. The ability to assess and monitor this response in the lungs of COPD patients is important for understanding the pathogenic mechanisms, but also provides a measure of the activity of the disease. Disease activity is more likely to relate to lung inflammation rather than the degree of airflow limitation as measured by the FEV1. Preliminary studies have shown the 18F fluorodeoxyglucose positron emission tomography (18F FDG-PET) signal, as a measure of lung inflammation, is quantifiable in the lungs and is increased in COPD patients compared to controls. However, the methodology requires standardisation and any further enhancement of the methodology would improve its application to assess inflammation in the lungs. I investigated various methods of assessing FDG uptake in the lungs and assessed the reproducibility of these methods, and particularly evaluated whether the data was reproducible or not in the COPD patients (smokers and ex-smokers). This data was then compared with a group of healthy controls to assess the role of dynamic 18F FDG-PET scanning as a surrogate marker of lung inflammation. My data showed a good reproducibility of all methods of assessing FDG lung uptake. However, using conventional Patlak analysis, the uptake was not statistically different between COPD and the control group. Encouraging results in favour of COPD patients were nonetheless shown using compartmental methods of assessing the FDG lung uptake, suggesting the need to correct for the effect of air and blood (tissue fraction effect) when assessing this in a highly vascular organ like the lungs. A prospective study analysis involving a bigger cohort of COPD patients would be desirable to investigate this further.

No description available.

A reconstruction algorithm in computerized tomography is a procedure for reconstructing the attenuation coefficientscient, a real-valued function associated with the object of interest, from the measured projection data. Generally speaking, reconstruction algorithms in CT fall into two categories: direct, e.g., filtered back-projection (FBP), or iterative. In this thesis, we discuss a new fast matrix-free iterative reconstruction method based on a polyenergetic model. While most modern x-ray CT scanners rely on the well-known filtered back-projection algorithm, the corresponding reconstructions can be corrupted by beam hardening artifacts. These artifacts arise from the unrealistic physical assumption of monoenergetic x-ray beams. In this thesis, to compensate, we use an alternative model that accounts for differential absorption of polyenergetic x-ray photons and discretize it directly. We do not assume any prior knowledge about the physical properties of the scanned object. We study and implement different solvers and nonlinear unconstrained optimization methods, such as a Newton-like method and an extension of the Levenberg-Marquardt-Fletcher algorithm. We explain how we can use the structure of the Radon matrix and the properties of FBP to make our method matrix-free and fast. Finally, we discuss how we regularize our problem by applying different regularization methods, such as Tikhonov and regularization in the 1-norm. We present numerical reconstructions based on the associated nonlinear discrete formulation incorporating various iterative optimization methods.

No description available.

A reconstruction algorithm in computerized tomography is a procedure for reconstructing the attenuation coefficientscient, a real-valued function associated with the object of interest, from the measured projection data. Generally speaking, reconstruction algorithms in CT fall into two categories: direct, e.g., filtered back-projection (FBP), or iterative. In this thesis, we discuss a new fast matrix-free iterative reconstruction method based on a polyenergetic model. While most modern x-ray CT scanners rely on the well-known filtered back-projection algorithm, the corresponding reconstructions can be corrupted by beam hardening artifacts. These artifacts arise from the unrealistic physical assumption of monoenergetic x-ray beams. In this thesis, to compensate, we use an alternative model that accounts for differential absorption of polyenergetic x-ray photons and discretize it directly. We do not assume any prior knowledge about the physical properties of the scanned object. We study and implement different solvers and nonlinear unconstrained optimization methods, such as a Newton-like method and an extension of the Levenberg-Marquardt-Fletcher algorithm. We explain how we can use the structure of the Radon matrix and the properties of FBP to make our method matrix-free and fast. Finally, we discuss how we regularize our problem by applying different regularization methods, such as Tikhonov and regularization in the 1-norm. We present numerical reconstructions based on the associated nonlinear discrete formulation incorporating various iterative optimization methods.

The purpose of this research was to compare skeletal and dental changes assessed by digital volumetric images produced during and after rapid maxillary expansion (RME) between a bone-borne anchored expansion appliance and a conventional tooth-borne RME. Initial steps included the development of a methodology to analyze CBCT images. Reliability of traditional two dimensional (2D) cephalometric landmarks identified in CBCT images was explored, and new landmarks identifiable on the CBCT images were also evaluated. This methodology was later tested through a clinical trial with 62 patients where skeletal and dental changes found after maxillary expansion using either a bone-borne or tooth-borne maxillary expander and compared to a non-treated control group. The conclusions that were obtained from this thesis were that the NewTom 9” and 12” three dimensional (3D) images present a 1-to-1 ratio with real coordinates, linear and angular distances obtained by a coordinate measurement machine (CMM). Landmark intra- and inter-reliability (ICC) was high for all CBCT landmarks and for most of the 2D lateral cephalometric landmarks. Foramen Spinosum, foramen Ovale, foramen Rotundum and the Hypoglossal canal all provided excellent intra-observer reliability and accuracy. Midpoint between both foramen Spinosums (ELSA) presented a high intra-reliability and is an adequate landmark to be used as a reference point in 3D cephalometric analysis. ELSA, both AEM and DFM points presented a high intra-reliability when located on 3D images. Minor variations in location of these landmarks produced unacceptable uncertainty in coordinate system alignment. The potential error associated with location of distant landmarks is unacceptable for analysis of growth and treatment changes. Thus, an alternative is the use of vectors. Selection of landmarks for use in 3D image analysis should follow certain characteristics and modifications in their definitions should be applied. When measuring 3D maxillary complex structural changes during maxillary expansion treatments using CBCT, both tooth-anchored and bone-anchored expanders presented similar results. The greatest changes occurred in the transverse dimension while changes in the vertical and antero-posterior dimension were negligible. Dental expansion was also greater than skeletal expansion. Bone-anchored maxillary expanders can be considered as an alternative choice for tooth-anchored maxillary expanders. / Medical Sciences in Orthodontics

Este trabalho trata da reconstrução tomográfica bidimensional e tridimensional, a partir de projeções, visando sua utilização em qualquer aplicação que necessite do volume completo do objeto em questão ou que necessite das imagens adquiridas dos- objetos projetados. Propicie-se utilizar um dos métodos pelo qual a tomografia Computadorizada gera as fatias bidimensionais do corpo exposto, expandindo-o para a terceira dimensão. Para tornar isto possível, é necessário o estudo de métodos de reconstrução-bidimensional, bem como a implementação de um deles. E desenvolvido, então, um estudo sobre os conceitos da tomografia computadorizada, seus diferentes tipos, contendo, os métodos de reconstruçãobidimensional utilizado por elas, alem, dos métodos de aquisição das projeções dos objetos a serem reconstruídos. E apresentada uma proposta de trabalho bidimensional, onde será implementado, alem do algoritmo de reconstrução, o processo de aquisição das projeções do objeto em questão, bem como, a modelagem do mesmo. Além, do desenvolvimento de uma proposta de trabalho tridimensional, onde o método de reconstrução bidimensional desenvolvido será expandido para a terceira dimensão e implementado, juntamente com o processo de aquisição dos objetos tridimensionais projetados, bem como, a modelagem dos mesmos. Um protótipo para cada uma destas propostas é gerado, contendo, cada um, a etapa de aquisição das imagens projetadas, e a etapa de reconstrução do objeto. Tanto os resultados da imagem sendo reconstruída, como as imagens adquiridas dos objetos projetados, são Bravados em arquivos. Por fim, é apresentada uma analise dos resultados gerados por estes protótipos, no que diz respeito a convergência de seus algoritmos, e a melhor maneira de utilizá-los, a fim de se obter um melhor resultado. / This paper is about bidimensional and tridimensional tomographic reconstruction working with projections in order to use in any application that needs complete volume of the object used or that needs images of the projected objects acquired. It is used one of the methods by which the computerized tomography generates bidimensional slices of the exposed body expanding it to third dimension. In order to make it possible it was necessary to study bidimensional reconstruction methods, as well as implementing one of them. It is developed a study on concepts of computerized tomography, its different types, including bidimensional reconstruction methods used by them, besides the methods used to acquire projections of the objects to be reconstructed. It is presented a proposal of the bidimensional work, where it will be implemented, besides the reconstruction algorithm, the aquisition process of the projection of the meant objects, as well as modelling them. It is also developed a proposal of a tridimensional work, where the bidimensional reconstruction method developed will be implemented and expanded to third dimension as well as the process of aquisition of the tridimensionals projected objects as well as modelling them. A prototype of these proposals is generated , containing each one the aquisition step of the projected images and the reconstruction step of the object. The results of the reconstructed image as well as the acquired images of the projected objects are saved in files. Finally it is presented an analysis of the generated results of the prototypes as to the convergence of these algorithms and the best way to use them in order to obtain a better result.

Este trabalho trata da reconstrução tomográfica bidimensional e tridimensional, a partir de projeções, visando sua utilização em qualquer aplicação que necessite do volume completo do objeto em questão ou que necessite das imagens adquiridas dos- objetos projetados. Propicie-se utilizar um dos métodos pelo qual a tomografia Computadorizada gera as fatias bidimensionais do corpo exposto, expandindo-o para a terceira dimensão. Para tornar isto possível, é necessário o estudo de métodos de reconstrução-bidimensional, bem como a implementação de um deles. E desenvolvido, então, um estudo sobre os conceitos da tomografia computadorizada, seus diferentes tipos, contendo, os métodos de reconstruçãobidimensional utilizado por elas, alem, dos métodos de aquisição das projeções dos objetos a serem reconstruídos. E apresentada uma proposta de trabalho bidimensional, onde será implementado, alem do algoritmo de reconstrução, o processo de aquisição das projeções do objeto em questão, bem como, a modelagem do mesmo. Além, do desenvolvimento de uma proposta de trabalho tridimensional, onde o método de reconstrução bidimensional desenvolvido será expandido para a terceira dimensão e implementado, juntamente com o processo de aquisição dos objetos tridimensionais projetados, bem como, a modelagem dos mesmos. Um protótipo para cada uma destas propostas é gerado, contendo, cada um, a etapa de aquisição das imagens projetadas, e a etapa de reconstrução do objeto. Tanto os resultados da imagem sendo reconstruída, como as imagens adquiridas dos objetos projetados, são Bravados em arquivos. Por fim, é apresentada uma analise dos resultados gerados por estes protótipos, no que diz respeito a convergência de seus algoritmos, e a melhor maneira de utilizá-los, a fim de se obter um melhor resultado. / This paper is about bidimensional and tridimensional tomographic reconstruction working with projections in order to use in any application that needs complete volume of the object used or that needs images of the projected objects acquired. It is used one of the methods by which the computerized tomography generates bidimensional slices of the exposed body expanding it to third dimension. In order to make it possible it was necessary to study bidimensional reconstruction methods, as well as implementing one of them. It is developed a study on concepts of computerized tomography, its different types, including bidimensional reconstruction methods used by them, besides the methods used to acquire projections of the objects to be reconstructed. It is presented a proposal of the bidimensional work, where it will be implemented, besides the reconstruction algorithm, the aquisition process of the projection of the meant objects, as well as modelling them. It is also developed a proposal of a tridimensional work, where the bidimensional reconstruction method developed will be implemented and expanded to third dimension as well as the process of aquisition of the tridimensionals projected objects as well as modelling them. A prototype of these proposals is generated , containing each one the aquisition step of the projected images and the reconstruction step of the object. The results of the reconstructed image as well as the acquired images of the projected objects are saved in files. Finally it is presented an analysis of the generated results of the prototypes as to the convergence of these algorithms and the best way to use them in order to obtain a better result.

Made available in DSpace on 2014-06-11T19:23:07Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-03-02Bitstream added on 2014-06-13T20:29:55Z : No. of bitstreams: 1 cremonini_ccr_me_botfm.pdf: 1144679 bytes, checksum: bf9c1e1e39c197477cae8519b0e360ce (MD5) / Fundação Pio Xii - Barretos / Avaliar a ocorrência e a gravidade das reações adversas agudas (RAA) com o uso do meio de contraste iodado iônico e não-iônico nos pacientes submetidos ao exame de tomografia computadorizada (TC) em hospital nacional terciário oncológico e avaliar neoplasia como possível risco para RAA. Secundariamente, avaliar o impacto do uso seletivo do meio de contraste iodado nos custos. Pacientes submetidos à TC com contraste iodado entre outubro de 2007 e agosto de 2008 foram avaliados quanto à ocorrência e à gravidade das reações adversas agudas aos meios de contrastes iônicos e nãoiônicos. As reações foram categorizadas em leve, moderada ou grave de acordo com o tipo dos sinais e sintomas e classificadas como agudas pelo tempo de ocorrência, desde o momento da injeção até 30 minutos após. Os testes do quiquadrado e exato de Fisher foram utilizados para análise estatística da ocorrência de RAA em relação às variáveis de gênero e idade. O estudo foi aprovado pelo Comitê de Ética local e o Termo de Consentimento Livre Esclarecido foi obtido. Houve 78 RAA ao contraste iodado iônico e 11 ao não-iônico, com uma ocorrência global de 3,3% (78/2.339) e 0,5% (11/2.216), respectivamente. A maioria das reações foi classificada como leve em ambos os grupos, representando 91% (71) no grupo iônico e 81,8% (9) no grupo não-iônico. As demais reações foram do tipo moderada não havendo nenhuma reação grave. Em relação ao início das RAA, 71% e 73% (iônico e não-iônico) ocorreram nos primeiros 5 minutos. A freqüência de RAA no grupo em que recebeu contraste iônico foi maior no sexo feminino (p < 0,001). No grupo não-iônico não houve diferença estatisticamente significativa entre os sexos (p = 1,0). Não houve associação entre a presença de reação aguda e as faixas... / To evaluate the occurrence and severity of acute adverse reactions (AAR) to iodinated ionic and non-ionic contrast media in patients undergoing computerized tomography (CT) at a national tertiary cancer hospital and to evaluate neoplasm as a possible risk for AAR. Secondly, to assess the impact of selective use of iodinated contrast agent costs. Patients who underwent contrast-enhanced CT between October 2007 and August 2008 were evaluated for the presence and severity of acute adverse reactions to ionic and non-ionic contrast media. The reactions were categorized as mild, moderate or severe according to the type of signs and symptoms and classified as acute by the time of occurrence, from the time of the injection up to 30 minutes afterwards. The chi-square and Fisher’s exact were used for statistical analysis of the occurrence of AAR for the variables of gender and age. The study was approved by the local Ethics Committee and informed consent was obtained. There were 78 AAR to ionic iodinated contrast and 11 to non-ionic, with an overall occurrence of 3.3% (78/2339) and 0.5% (11/2216), respectively. Most reactions were classified as mild in both groups, representing 91% (71) in the ionic group and 81.8% (9) in the non-ionic group. All other reactions were moderate and there were no severe reactions. Regarding onset of AAR, 71% and 73% (ionic and non-ionic group) occurred in the first five minutes. The occurrence of AAR in the group who received ionic contrast was higher in females (p <0.001). As for the non-ionic group, there was no significant statistical difference between genders (p = 1.0). There was no association between the presence of acute reaction and the age groups of the population in the ionic contrast group. For the non-ionic group, no statistical analysis was performed as the sample was deemed reduced. Among... (Complete abstract click electronic access below)

Made available in DSpace on 2014-10-09T12:27:01Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:58:16Z (GMT). No. of bitstreams: 0 / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP