Este trabalho descreve o desenvolvimento de um sistema de \"software\" para processamento, visualização e manipulação de imagens tomográficas obtidas por RM. Primeiramente, foi desenvolvido um sistema para uma estação de trabalho Interpro 32&#176C, da Intergraph. Este sistema foi desenvolvido de forma amigável, utilizando-se janelas e \"menus\", para efetuar a interação com o usuário. Foram analisadas e implementadas várias operações de processamento de imagens, tais como: filtros digitais, manipulação da imagem através do seu histograma e medidas estatísticas sobre regiões da imagem. A experiência e o conhecimento obtido com esta implementação, (oram utilizados para definir e desenvolver um novo ambiente gráfico, para uma arquitetura de \"hardware\" baseada no processador gráfico TMS34010 da Texas Instruments, previamente desenvolvida no Laboratório de Instrumentação Eletrônica (LIE). Este ambiente, que suporta menus e janelas, foi desenvolvido utilizando-se das instruções gráficas inerentes à família TMS340. Foram desenvolvidas rotinas de comunicação com o hospedeiro, as quais permitem, por exemplo, que as imagens armazenadas no hospedeiro sejam transmitidas para a arquitetura dedicada. As mesmas rotinas foram utilizadas para depurar e validar o sistema gráfico. / The present work describes the development of a software system to process, visualize and manipulate Magnetic Resonance Images. First an application software W8S developed for an Interpro 32&#176C Intergraph workstation. In this menu and window based 8Oftware, image operations such as filters, transformations and image manipulation based on histograms with statistical data was implemented and evaluated. The knowledge and experience obtained with this implementation was subsequently used to define and design a new graphic environment for a dedicated TMS340 based hardware architecture previously developed in our laboratory. This new toolkit provides window and menu support, and was developed through extensive use of the powerful TMS340 native graphics instructions. Debugging and tracing routines were developed based on an implemented host (PC) - graphics processor board communication system. The same communication software was also used in the examples to perform menu selected downloads of images and functions from the host.

Neste trabalho, é apresentado um novo modelo de reconstrução tridimensional (3D) para amostras agrícolas com filtragem de Wiener em processamento paralelo, o qual é obtido a partir de reconstruções tomográficas bidimensionais (2D). No desenvolvimento, foram modelados algoritmos paralelos de retroprojeção filtrada e reconstrução tridimensional, baseando-se na inserção de um conjunto de planos virtuais entre pares de planos reais obtidos em ensaios tomográficos de raios X na faixa de energia de 56 keV a 662 keV. No modelo, os planos virtuais gerados em algoritmo paralelo são implementados com base na técnica de interpolação por B-Spline-Wavelet. Para validação do modelo desenvolvido, foi utilizada uma plataforma paralela composta de 4 processadores DSP, a qual possibilitou a troca de dados entre os processadores DSP e o envio de informações para o host, um computador desktop com processador Pentium III operando em 800 MHz. A extração de medidas de eficiência, de ganho e de precisão dos algoritmos paralelos foi realizada com base em um conjunto de amostras agrícolas (solo, vidro e madeiras) e de phantoms de calibração. Nessa avaliação, observou-se que o algoritmo de reconstrução 2D, utilizado como base para o algoritmo de reconstrução 3D, possibilitou uma alta eficiência para imagens de maior resolução, atingindo um pico de 92% de eficiência na resolução de 181X181 pixels. O algoritmo paralelo de reconstrução 3D foi analisado para um conjunto de amostras, sob diferentes configurações de planos reais e virtuais, organizados de forma a possibilitarem a avaliação do impacto causado pelo aumento da granularidade da comunicação e da carga de trabalho. Um melhor desempenho, com ganho médio igual a 3,4, foi obtido na reconstrução de objetos que demandaram o cálculo de um maior número de planos. Também, buscou-se conhecer a adaptabilidade do modelo para uso em arquitetura convencional, sendo que neste caso o uso de MPI permitiu a comunicação entre as tarefas projetadas em cada algoritmo paralelo. Adicionamente, foram incluídas ferramentas de visualização 2D e 3D para que usuários possam analisar as imagens e as características das amostras agrícolas em ambiente tridimensional. Os resultados obtidos indicam que o modelo de reconstrução 3D paralela trouxe contribuições originais para a área de tomografia agrícola aplicada à física de solos, bem como para a criação de ferramentas que viabilizem explorar recursos computacionais disponíveis em arquiteturas paralelas que demandem elevada capacidade de processamento. / This work presents a new method for three dimensional (3D) image reconstruction dedicated to the investigation in soil physics by means of X-ray tomography which is obtained using two-dimensional (2D) tomographic image reconstructed slices. The conception of the 3D model for reconstruction and visualization was based on the filtered back projection algorithm, operating under parallel environment together the insertion of virtual planes between pairs of real planes obtained by X-Ray tomography under energies varying from 56 keV to 662 keV. In this model, the virtual planes were generated by interpolation with the use of B-Spline-Wavelets. The evaluation of the 3D reconstruction model was established by using a set of agricultural samples (i.e., soil, glass, wood and calibration phantoms) having different configuration for the planes. Such configuration was based on setting not only the sizes and the number of the real but also the virtual planes in the volume. This procedure allows the impact measurements as a function of the increasing in workload and the communication granularity. To validate the reconstruction model, a dedicated parallel architecture composed of 4 DSP processors was used. This board enables data exchange between DSP processors and communication with host computer. A measurement of efficiency with a speed up equal to 3.4 was obtained using the same set of samples and a better performance was observed with a higher number of planes. Also, to understand about its adaptability, the model was implemented in conventional architecture, using MPI library to enable communication between designed tasks. Additionally, 2D and 3D visualization tools based on Vizualization ToolKit were included in order to help users to analyze images and their characteristics. Results have shown that the 3D parallel model reconstruction brought original contributions for the soil science diagnosis by X-Ray tomography, as well as to explore the available computational resources in parallel architectures, which demands great processing capacity.

O aumento ósseo de rebordos mandibulares posteriores atróficos continua sendo um grande desafio para os cirurgiões orais. Sabe-se que o osso alógeno pode ser utilizado para realização de enxertos aposicionais nessa região, com bons resultados clínicos e histomorfométricos, porém não há estudos sobre a manutenção óssea volumétrica desses enxertos em longo prazo. O objetivo deste estudo foi avaliar tomograficamente, por meio de medidas lineares e volumétricas, a dinâmica de manutenção do osso alógeno córtico-medular fresco congelado em bloco na cirurgia de aumento ósseo de rebordos mandibulares posteriores atróficos em humanos. Os pacientes do estudo foram submetidos à realização de enxertos aposicionais de osso alógeno fresco congelado em bloco na região posterior mandíbula. Os blocos foram modelados manualmente, fixados aos leitos receptores com parafusos de titânio de 1,5 x 10,0 mm e recobertos com osso mineral bovino e membrana absorvível de colágeno suíno. Para avaliação do ganho ósseo em altura, espessura e volume, cada paciente foi submetido a exames de tomografia computadorizada de feixe cônico (TCFC) em 03 períodos experimentais: imediatamente após a cirurgia de enxerto (T1); 06 meses após a enxertia, no momento de instalação dos implantes (T2) e 01 ano após a carga funcional protética (T3). Os dados obtidos foram tabulados e submetidos à análise estatística por meio do teste de Kruskal-Wallis seguido do post test de Tukey. Para comparação entre dois grupos, foram empregados os testes t de Student e Mann-Whitney. Foram operados 20 pacientes, 15 mulheres e 05 homens, com idade entre 37 e 64 anos (51,8 ± 7,5 anos), para os quais um total de 50 blocos ósseos foi utilizado. Dos 50 blocos, 8% foram utilizados para aumento ósseo em altura, 50% para espessura e 42% para altura e espessura. O ganho ósseo em altura foi de T1 = 5,15 ± 1,04 mm, T2 = 3,91± 0,94 mm e T3 = 2,92 ± 0,71 mm; em espessura, foi de T1 = 6,42 ± 1,20 mm, T2 = 4,64 ± 1,32 mm e T3 = 4,02 ± 0,71 mm. O ganho ósseo em volume foi de T1 = 1176,62 ± 358,08 mm³, T2 = 785,78 ± 201,16 mm³ e T3 = 689,72 ± 187,45 mm³. Foi observada diferença estátistica entre os três tempos experimentais tanto para altura quanto para espessura. Porém, volumetricamente, não foi possível observar diferença entre T2 e T3. No total, foram instalados 50 implantes (01 implante/bloco), para os quais foi obtida uma taxa de sobrevivência de 96% após 31,75 ± 6,99 meses de acompanhamento pós-operatório. Com base nos resultados obtidos, pode-se concluir que o osso alógeno fresco congelado em bloco constitui uma alternativa viável para cirurgia de aumento de rebordo mandibulares posteriores atróficos, apresentando uma manutenção volumétrica aceitável em longo prazo e permitindo a instalação de implantes com alta taxa de sucesso. / Atrophic posterior mandible bone augmentation remains a major challenge for oral surgeons. It is known that allogenic bone can be used for appositional grafts in this region, with good clinical and histomorphometric results, howerer there are no long term studies on the volumetric bone maintenance of these grafts. The objective of this study was to evaluate tomographically, through linear and volumetric measurements, the dynamic maintenance of corticocancellous fresh frozen allograft bone blocks for atrophic posterior mandible augmentation in humans. The patients of the study were submitted to fresh frozen allograft bone block appositional grafting surgery in the posterior mandible. The blocks were manually shaped, fixed to the recipient bed with 1.5 x 10.0 mm titanium screws and covered with bovine bone mineral and porcine collagen absorbable membrane. For assessment of bone gain in height, thickness and volume, each patient underwent cone beam computed tomography (CBCT) at 03 experimental periods: immediately after grafting surgery (T1); 06 months after grafting, at the implant placement (T2) and 01 year after prosthetic functional loading (T3). Data were tabulated and submitted to statistical analysis using the Kruskal-Wallis test followed by Tukey post test. For comparison between two groups, Student t test and Mann-Whitney were employed. Twenty patients were operated, 15 women and 05 men, aged between 37 and 64 years (5.8 ± 7.5 years), for which a total of 50 bone blocks was used. Of the 50 blocks, 8% were used for bone augmentation in height, 50% in thickness and 42% for both height and thickness. The bone gain in height was 5.15 ± 1.04 T1 = mm, T2 = 3.91 ± 0.94 mm and T3 = 2.92 ± 0.71 mm; while in thickness was T1 = 6.42 mm ± 1.20, 4.64 ± T2 = T3 = 1.32 mm and 4.02 ± 0.71 mm. The bone gain in volume was T1 = 1176.62 ± 358.08 mm³, T2 = 785.78 ± 201.16 mm³ and T3 = 689.72 ± 187.45 mm³. Statistical difference was observed between the three experimental times for both height and thickness. However, volumetrically, no difference was observed between T2 and T3. Fifty implants were installed (01 implant/block), with a survival rate of 96% after 31.75 ± 6.99 months of postoperative follow-up. Based on these results, it can be concluded that the fresh-frozen allograft bone block is a viable alternative for atrophic posterior mandible augmentation, presenting an acceptable long-term volumetric bone maintenance and allowing dental implant installation with high success rates.

Made available in DSpace on 2017-07-21T19:26:00Z (GMT). No. of bitstreams: 1 Jaqueline Borges.pdf: 2739563 bytes, checksum: d03b8e7308ae59a90b2d872a90cad206 (MD5) Previous issue date: 2011-03-11 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Computed tomography (CT) is a technique that provides images of sample cross sections of porous media. The technique has shown efficient to investigate different soil physical phenomena since its first use in soil science in 1982. One of the most widely investigated issues in physics applied to porous media regards the definition of representative elementary areas (REA) to measure the soil physical properties. REA is related to the minimum area of a sample needed to represent its characteristics of interest. The objective of this work was to define REAs to be adopted for density and porosity measurements in clod samples of a clay soil. The equipment used was a first generation tomograph with 241Am source, with millimetric resolution (1.1 x 1.1 mm2). The photon detection was made with a plane NaI(Tl) solid crystal scintillator. Clods (18 samples) were also submitted to the clod method (standard method) in order to determine its. In order to reconstruct tomographic images, the program Microvis developed by Embrapa/CNPDIA was used. Concentric square areas with sizes ranging from 1.2 to 1162.8 mm2 were selected. To define REA for the following criteria were adopted: average value relative deviation between the last and each of the remaining areas not superior to 5%, 4%, 3%, 2% and 1%; and 2) that at least three consecutive areas cannot differ among themselves, using the variation criterion in item 1. The measurements through the clod method presented variation coefficient of 3.8%. Thus, it was considered that the REA was reached at the 4% variation criterion. For the criterion is similar, but the relative deviation considered cannot be superior to 10%. The REA defined for measurements corresponds to 640.1 mm2. On the other hand, for the REA found was 882.1 mm2. So, in order to carry out representative measurements of these two physical properties the REA must be at least 882.1 mm2. Key-words: Representative Measurements. Tomographic Images. Porous Media. / A Tomografia Computadorizada (TC) trata-se de uma técnica que fornece imagens de seções transversais de amostras de meios porosos. A técnica tem se mostrado eficaz na investigação de diversos fenômenos físicos do solo desde sua primeira aplicação nessa área em 1982. Uma questão amplamente investigada em física aplicada a meios porosos diz respeito à definição de áreas elementares representativas (AER) para medidas de propriedades físicas do solo. A AER está relacionada com a área mínima de uma amostra, necessária para representar suas características de interesse. O objetivo deste trabalho foi definir AERs a serem adotadas para medidas da densidade e porosidade de amostras de torrão de um solo de textura argilosa. Para isso, utilizou-se um tomógrafo de primeira geração, equipado com fonte de 241Am com resolução da ordem de milímetros (1,1 x 1,1 mm2). A detecção dos fótons foi feita com um detector de cintilação sólida de NaI(Tl) do tipo plano. Os torrões (18 amostras) também foram submetidos ao método do torrão parafinado (TP, método padrão) para determinação da sua Para reconstrução das imagens tomográficas utilizou-se o programa Microvis desenvolvido pela Embrapa/CNPDIA. Nestas imagens foram selecionadas áreas quadrangulares concêntricas com dimensões variando de 1,2 até 1162,8 mm2. Para definição da AER para foram utilizados os seguintes critérios: 1) desvio relativo do valor médio entre a última e cada uma das demais áreas não superior a 5%, 4%, 3%, 2% e 1% e 2) que pelo menos três áreas consecutivas não devem diferir entre si, utilizando o critério de variação do item 1. As medidas de pelo método do TP apresentaram coeficiente de variação da ordem de 3,8%. Assim, considerou-se que a AER foi atingida no critério de 4% de variação. Para o critério é semelhante, mas o desvio relativo considerado não deve ser superior a 10%. A AER definida para medidas de corresponde a 640,1 mm2. Para a AER encontrada é de 882,1 mm2. Portanto, para a realização de medidas representativas destas duas propriedades físicas, a AER deve ser de pelo menos 882,1 mm2. Palavras-chave: Medidas Representativas. Imagens Tomográficas. Meios Porosos.

Uma das complicações mais importantes relacionadas com o tratamento de implante dentário é a peri-implantite. Devido a limitação pela sobreposição de estruturas da técnica periapical, nos casos da perda óssea peri-implantar nas faces vestibulares e linguais ou palatais necessita-se de um exame capaz de prover imagens em 3 dimensões para o correto diagnóstico, sendo as imagens de tomografia computadorizada por feixe cônico (TCFC) as mais indicadas. O objetivo deste estudo foi avaliar a acurácia, especificidade, sensibilidade, concordância inter e intraobservadores e determinar a influência dos artefatos na detecção dos defeitos ósseos peri-implantares simulados em mandíbulas humanas edêndulas secas. Foram utilizados dois aparelhos de TCFC com diferentes protocolos de aquisição: i-CAT Gendex CB-500(120kVp, 5mA) e ORTHOPANTOMOGRAPH OP300(90kVp, 6.3mA). Foram instalados 24 implantes dentários cilíndricos e executados dezesseis defeitos somente nas faces vestibulares, com os comprimentos que variaram de 0,5mm a 15mm. Somente cortes sagitais foram utilizados para avaliação qualitativa e quantitativa dos defeitos foi realizada por meio de Image J. Os resultados do teste de concordância intra e inter-observadores tanto nas avaliações qualitativas e quantitativas foram predominantemente fracos. Os valores de Área Sob a Curva (ASC) variaram de 0.51 a 0.72 no i-CAT Gendex CB-500; e no ORTHOPANTOMOGRAPH OP300 variaram de 0.54 a 0.75, demonstrando desempenho diagnóstico ligeiramente superior. Nas imagens obtidas em aparelho com 120kVp (i-CAT Gendex CB-500) foram observados maior contraste em relação ao aparelho 90kVp (ORTHOPANTOMOGRAPH® OP300); em aparelho com o menor kVp (OP300) formaram mais artefatos e estes, degradaram a qualidade das imagens e influenciaram o desempenho diagnóstico das TCFCs na detecção e nas mensurações de perda óssea peri-implantar. Os protocolos de aquisições diferentes podem influenciar no aumento ou redução da formação dos artefatos. / One of the most important complications related to dental implant treatment is periimplantitis. Due to the structures overlapping inherited to periapical technique, in cases of buccal and lingual or palatal bone loss in peri-implantitis, the 3 dimensions observation exam like cone beam computed tomography(CBCT) is most indicated. The objective of this study was to evaluate the accuracy, specificity, sensitivity, interand intra-observer agreement and to determine the influence of the artifacts in the detection of the peri-implant bone defects simulated in human dry mandibles. The two CBCT devices with different acquisition protocols were used in this study: i-CAT Gendex CB-500 (120kVp, 5mA) and ORTHOPANTOMOGRAPH OP300 (90kVp, 6.3mA). Twenty-four cylindrical dental implants were placed and 16 defects were prepared only on buccal faces, the defect lengths ranged from 0.5mm to 15mm. For qualitative and quantitative assessment, only sagittal slices were evaluated by the observers, using Image J software. The results of intra and inter-observer agreement tests in both assessments were generally poor. The AUC values ranged from 0.51 to 0.72 on the i-CAT Gendex CB-500; and in the ORTHOPANTOMOGRAPH OP300 ranged from 0.54 to 0.75, showing slightly higher diagnostic performance. Higher contrast was observed in the 120 kVp device\'s images (i-CAT Gendex CB-500) when compared with the 90 kVp device\'s image (ORTHOPANTOMOGRAPH® OP300). The low kVp device (OP300), formed more artifacts which degraded the image quality and influenced the CBCT diagnostic performance in the detection and measurement of peri-implant bone loss. Different CBCT acquisition protocols may influence increasing or reducing artefact formation.

The problem of reconstructing an image from a set of tomographic data is not new, nor is it lacking attention. However there is still a distinct gap between the mathematicians and the experimental scientists working in the computed tomography (CT) imaging community. One of the aims in this thesis is to bridge this gap with mathematical reconstruction algorithms and analysis approaches applied to practical CT problems. The thesis begins with an extensive analysis for assessing the suitability of reconstruction algorithms for a given problem. The paper presented examines the idea of extracting physical information from a reconstructed sample and comparing against the known sample characteristics to determine the accuracy of a reconstructed volume. Various test cases are studied, which are relevant to both mathematicians and experimental scientists. These include the variance in quality of reconstructed volume as the dose is reduced or the implementation of the level set evolution method, used as part of a simultaneous reconstruction and segmentation technique. The work shows that the assessment of physical attributes results in more accurate conclusions. Furthermore, this approach allows for further analysis into interesting questions in CT. This theme is continued throughout the thesis. Recent results in compressive sensing (CS) gained attention in the CT community as they indicate the possibility of obtaining an accurate reconstruction of a sparse image from severely limited or reduced amount of measured data. Literature produced so far has not shown that CS directly guarantees a successful recovery in X-ray CT, and it is still unclear under which conditions a successful sparsity regularized reconstruction can be achieved. The work presented in the thesis aims to answer this question in a practical setting, and seeks to establish a direct connection between the success of sparsity regularization methods and the sparsity level of the image, which is similar to CS. Using this connection, one can determine the sufficient amount of measurements to collect from just the sparsity of an image. A link was found in a previous study using simulated data, and the work is repeated here with experimental data, where the sparsity level of the scanned object varies. The preliminary work presented here verifies the results from simulated data, showing an "almost-linear" relationship between the sparsity of the image and the sufficient amount of data for a successful sparsity regularized reconstruction. Several unexplained artefacts are noted in the literature as the `partial volume', the 'exponential edge gradient' or the 'penumbra' effect, with no clear explanation for their cause, or established techniques to remove them. The work presented in this paper shows that these artefacts are due to a non-linearity in the measured data, which comes from either the set up of the system, the scattering of rays or the dependency of linear attenuation on wavelength in the polychromatic case. However, even in monochromatic CT systems, the non-linearity effect can be detected. The paper shows that in some cases, the non-linearity effect is too large to ignore, and the reconstruction problem should be adapted to solve a non-linear problem. We derive this non-linear problem and solve it using a numerical optimization technique for both simulatedand real, gamma-ray data. When compared to reconstructions obtained using the standard linear model, the non-linear reconstructed images show clear improvements in that the non-linear effect is largely eliminated. The thesis is finished with a highlight article in the special issue of Solid Earth, named "Pore-scale tomography & imaging - applications, techniques and recommended practice". The paper presents a major technical advancement in a dynamic 3D CT data acquisition, where the latest hardware and optimal data acquisition plan are applied and as a result, ultra fast 3D volume acquisition was made possible. The experiment comprised of fast, free-falling water-saline drops traveling through a pack of rock grains with varying porosities. The imaging work was enhanced by the use of iterative methods and physical quantification analysis performed. The data acquisition and imaging work is the first in the field to capture a free falling drop and the imaging work clearly shows the fluid interaction with speed, gravity and more importantly, the inter- and intra-grain fluid transfers.

Les pathologies cardio-vasculaires d’origine athéroscléreuse, premières causes de mortalité dans les pays occidentaux, sont insuffisamment prises en charge par les outils de dépistage et de suivi thérapeutique actuels. La Tomographie par Emission de Positons (TEP) est susceptible d’apporter au clinicien des outils puissants pour le diagnostic et le suivi thérapeutique des patients, en particulier grâce au traceur Fluorodésoxyglucose marqué au fluor 18 ([18F]-FDG). Cependant, l’Effet de Volume Partiel (EVP), dû notamment à la résolution spatiale limitée dans les images (plusieurs millimètres) en regard des faibles dimensions (de l’ordre du millimètre) des VOlumes d’Intérêt (VOIs), et les fluctuations statistiques du signal mesuré présentent des défis pour une quantification fiable.Un modèle original de lésion athéromateuse, paramétré par ses dimensions et sa concentration d’activité, a été développé et des simulations Monte-Carlo d’acquisitions TEP au [18F]-FDG de 36 lésions ont été produites. A partir des acquisitions simulées, nous avons montré que le nombre d’itérations des reconstructions itératives, le post-filtrage appliqué et le moyennage dans le VOI,paramètres relevés comme hautement variables dans une revue de la littérature dédiée, peuvent induire des variations des valeurs de fixation mesurées d’un facteur 1.5 à 4. Nous avons montré qu’une modélisation de la réponse du tomographe pouvait réduire le biais de mesure d’environ 10% par rapport au biais mesuré sur une image reconstruite avec un algorithme itératif standard et pour un niveau de bruit comparable. Sur les images reconstruites, nous avons montré que la fixation mesurée reste très biaisée (sous-estimation de plus de 50% du SUV réel) et dépend fortement des dimensions de la lésion à cause de l’EVP. Un contraste minimum de 4 par rapport à l’activité sanguine est nécessaire pour qu’une lésion soit détectée. Sans correction d’EVP, la mesure présente une corrélation faible avec la concentration d’activité, mais est très corrélée à l’activité totale dans la lésion. L’application d’une correction d’EVP fournit une mesure moins sensible à la géométrie de la lésion et plus corrélée à la concentration d’activité mais réduit la corrélation à l’activité totale dans la lésion.En conclusion, nous avons montré que l’intégralité de la fixation du [18F]-FDG dans les lésions athéromateuses inflammatoires totale peut être caractérisée sur les images TEP. Cette estimée ne requiert pas de correction de l’EVP. Lorsque la concentration d’activité dans la lésion est estimée, les mesures sont très biaisées à cause de l’EVP. Ce biais peut être réduit en mesurant le voxel d’intensité maximale, dans les images reconstruites sans post-filtrage avec au moins 80 itérations incluant un modèle de réponse du détecteur. La mise en œuvre d’une correction d’EVP facilite la détection des changements d’activité métabolique indépendamment de changements de dimensions de la zone siègede l’inflammation. Une quantification absolue exacte de la concentration d’activité dans les lésions ne sera possible que via une amélioration substantielle de la résolution spatiale des détecteurs TEP. / Cardiovascular disease is the leading cause of death in western countries. New strategies and tools for diagnosis and therapeutic monitoring need to be developed to manage patients with atherosclerosis, which is one major cause of cardiovascular disease. Fluorodeoxyglucose Positron Emission Tomography (FDG-PET) is a powerful imaging technique that can detect at early stages plaques prone to rupture. Yet, Partial Volume Effect (PVE), due to the small lesion dimensions (around 1 mm) with respect to the scanner spatial resolution (around 6 mm full width at half maximum), and statistical variations considerably challenge the precise characterization of plaques from PET images. An original model of atheromatous lesion parameterized by its dimensions and activity concentration, was developed. Thirty six Monte Carlo simulations of FDG-PET acquisitions were produced. Based on the simulations, we showed that the number of iterations in iterative reconstructions, the post filtering of reconstructed images and the quantification method in the Volume Of Interests (VOI) varied sharply in an analysis of the dedicated literature. Changes in one of these parameters only could induce variations by a factor of 1.5 to 4 in the quantitative index. Overall, inflammation remained largely underestimated (> 50% of the real uptake). We demonstrated that modeling the detector response could reduce the bias by 10% of its value in comparison to a standard OSEM recontruction and for an identical level of noise. In reconstructed images, we showed that the measured values depended not only on the real uptake but also on the lesion dimensions because of PVE. A minimum contrast of 4 with respect to blood activity was required for the lesion to be observable. Without PVE correction, the measured values exhibited a correlation with activity concentration but were much more correlated with the total uptake in the lesion. Applying a PVE correction leads to an activity estimate that was less sensitive to the geometry of the lesion. The corrected values were more correlated to the activity concentration and less correlated to the total activity. In conclusion, we showed that the total activity in inflammatory lesions could be assessed in FDG-PET images. This estimate did not require PVE correction. Tracer concentration estimates are largely biased due to PVE, and the bias can be reduced by measuring the maximum voxel in the lesion in images reconstructed with at least 80 iterations and by modeling the detector response. Explicit PVE correction is recommended to detect metabolic changes independent of geometric changes. An accurate estimation of plaque uptake will however require the intrinsic spatial resolution of PET scanners to be improved.

A tunable snapshot imaging spectrometer has been demonstrated. A liquid crystal spatial light modulator (LC SLM) has been integrated into a computed tomographic imaging spectrometer (CTIS) to achieve tunability. The LC SLM allows for rapid, programmable, and non-mechanical alteration of its phase profile by the application of appropriate voltages to its transparent electrodes.The goal of this dissertation is twofold: (1) to integrate a liquid crystal spatial light modulator into a CTIS instrument and characterize its performance as a tunable CTIS disperser, and (2) to implement tunability by analyzing different CTIS configurations.The theoretical model of CTIS operation, calibration, reconstruction, and disperser design are covered in detail. The cross talk of the LC SLM forces the use of a feedback design algorithm rather than designing the desired phase profile a priori in the computer. The modifications to the current polychromatic linear inversion technique for use with the LC SLM in feedback are presented. The result of the modifications is the successful integration of a reprogrammable (i.e. tunable) disperser for the CTIS instrument.The implementation of tunability is explored by analyzing the spectral resolution of a reconstructed point source for different disperser configurations. A method for experimentally determining the CTIS spectral resolution is presented.

No description available.

Introdução: A terapia a laser de baixa intensidade (LLLT) é uma importante ferramenta na biomodulação tecidual quando do processo cicatricial de uma ferida ou dano cirúrgicos. A sua aplicação favorece o reparo ósseo na região de implantes dentários. Objetivos: Avaliar as alterações no processo de reparo ósseo perimplantar em alvéolo do incisivo inferior de coelho após exodontia seguido da instalação imediata de um implante osseointegrável, irradiado ou não com laser de baixa intensidade (AsGaAl) em diferentes parâmetros através da análise da densidade de imagem perimplantar por tomografia computadorizada de feixe cônico (TCFC) e histomorfométrica da interação entre osso e implante. Verificar a aplicabilidade da TCFC no controle pós-operatório de implantes dentários através de correlação com a microscopia óptica. Metodologia: A amostra foi composta por vinte e quatro fragmentos de mandíbulas dissecadas de coelhos contendo um implante dentário colocado após a exodontia. A distribuição das amostras foi realizada de forma que cada grupo conteve seis mandíbulas, sendo um grupo controle (C) e três grupos experimentais (EI, EII, EIII) seguindo o padrão de aplicação da laserterapia, nos animais in vivo durante 13 dias. O grupo controle recebeu aplicação de laser placebo. O grupo EI recebeu dose de 70J/cm2, o EII-35J/cm2 e o EIII-140J/cm2. Aos 45 dias do experimento todos os animais foram mortos tendo suas mandíbulas dissecadas e submetidas à TCFC para análise da densidade de imagem perimplantar através de dois métodos de avaliação (linear e área retangular). Após, as amostras foram incluídas em resina e preparadas para análise através de microscopia óptica. Na análise histomorfométrica foi mensurada a extensão linear de contato entre osso e implante (ELCOI), a área óssea por espira (AOE), a área óssea retangular (AOR) e a área de fibras colágenas (FC) das três espiras médias do implante. Resultados: Os resultados foram analisados através da análise de variância (ANOVA) complementada pelo teste de comparações múltiplas de Tukey ao nível de significância de 5%. Observou-se um aumento da ELCOI e da FC para o grupo EIII em comparação com os demais grupos. A avaliação linear por TCFC demonstrou médias de nível de cinza mais elevadas para o grupo EIII em comparação com os demais grupos e que os grupos EI e EII apresentaram valores maiores que o grupo C. A avaliação da área retangular por TCFC e avaliações histomorfométricas de área óssea retangular (AOR) e por espira (AOE) não apresentaram diferenças significativas entre os grupos. Não foi possível detectar correlação entre as análises dos resultados obtidos por histomorfometria e TCFC através do coeficiente de correlação de Pearson ao nível de significância de 5%. Conclusão: A LLLT biomodula positivamente o reparo ósseo perimplantar na dose de 140J/cm2. A densidade de imagem perimplantar avaliada pelos dois métodos propostos obtidos por TCFC não demonstrou correlação significativa com os resultados da histomorfometria, sendo discutível sua aplicação no controle pós-operatório de implantes dentários. / Introduction: The use of low level laser therapy (LLLT) is an important tool in tissue biomodulation during the healing process of a wound or surgical damage. The application promotes bone repair in the area of dental implants. Objectives: To evaluate the changes in the peri-implant bone healing in mandibular incisor alveoli of rabbits after extraction followed by immediate installation of an osseointegrated implant, irradiated or not with low intensity laser (GaAlAs) on different parameters by analyzing the image density perimplantar with cone beam computed tomography (CBCT) and histomorphometry of the interaction between bone and implant. Verify the applicability of CBCT in postoperative follow up of dental implants through correlation with optical microscopy. Methodology: The sample was composed of twenty-four fragments of dissected rabbits jaws containing a dental implant placed after the extraction. The distribution of samples was performed so that each group contained six jaws A sample was divided in one control group (C) and three experimental groups (EI, EII, EIII) in which the standard laser therapy was applied in live animals for 13 days. The control group received placebo laser application. The EI group received a dose 70J/cm2, EII-35J/cm2 and EIII-140J/cm2. At 45 days of the experiment all animals were killed and their mandibles were dissected and submitted for analysis to the CBCT image density perimplantar through two evaluation methods (linear and rectangular area). After the samples were embedded in resin and prepared for analysis by optical microscopy. In histomorphometry was measured the bone-implant contact (BIC), bone area within the implant threads (BAS), bone area rectangular (BAR) and the area of collagen fibers (CF) of three median spirals of the implant. Results: The results were analyzed by analysis of variance (ANOVA) complemented by the multiple comparison test of Tukey at a significance level of 5%. It was observed an increase in BIC and CF for the group EIII compared to the other groups. The CBCT linear evaluation demonstrated gray level averages higher for the group EIII compared to the other groups and that the groups EI and EII were higher than group C. The evaluation of the rectangular area by CBCT and ratings histomorphometric bone area rectangular (BAR) and within the implant threads (BAT) showed no significant differences between groups. There were no significant relation between the analyzes of the results obtained by histomorphometry and CBCT through the Pearson correlation coefficient at a significance level of 5%. Conclusion: LLLT modulates positively bone repair in the peri-implant with dose 140J/cm2. The image density perimplantar evaluated by the two proposed methods obtained by CBCT demonstrated no significant correlation with the results of histomorphometry, being moot its application in controlling postoperative dental implants.