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<p>Dual modality imaging systems such as SPECT/CT have become commonplace in medical imaging as it aids in diagnosing diseases by combining anatomical images with functional images. We are interested in developing a dual modality imaging system combining SPECT and MR imaging because MR does not require any ionizing radiation to image anatomical structures and it is known to have superior soft tissue contrast to CT. However, one of the fundamental challenges in developing a SPECT/MR system is that traditional gamma cameras with photomultiplier tubes are not compatible within magnetic fields. New development in solid state detectors has led to the silicon photomultiplier (SiPM), which is insensitive to magnetic fields.</p> <p>We have developed a small area gamma camera with a tileable 4x4 array of SiPM pixels coupled with a CsI(Tl) scintillation crystal. A number of simulated gamma camera geometries were performed using both pixelated and monolithic scintillation crystals. Several event positioning algorithms were also investigated as an alternative to conventional Anger logic positioning. Simulations have shown that we can adequately resolve intrinsic spatial resolution down to 1mm, even in the presence of noise. Based on the results of these simulations, we have built a prototype SiPM system comprised of 16 detection channels coupled to discrete crystals. A charge sensitive preamplifier, pulse height detection circuit and a digital acquisition system make up our pulse processing components in our gamma camera system. With this system, we can adequately distinguish each crystal element in the array and have obtained an energy resolution of 30±1 (FWHM) with Tc-99m (140keV). In the presence of a magnetic field, we have seen no spatial distortion of the resultant image and have obtained an energy resolution of 31±3.</p> / Master of Science (MSc)

<p>As the number of transistors that are integrated onto a silicon die continues to in- crease, the compute power is becoming a commodity. This has enabled a whole host of new applications that rely on high-throughput computations. Recently, the need for faster and cost-effective applications in form-factor constrained environments has driven an interest in on-chip acceleration of algorithms based on Monte Carlo simula- tions. Though Field Programmable Gate Arrays (FPGAs), with hundreds of on-chip arithmetic units, show significant promise for accelerating these embarrassingly paral- lel simulations, a challenge exists in sharing access to simulation data amongst many concurrent experiments. This thesis presents a compute architecture for accelerating Monte Carlo simulations based on the Network-on-Chip (NoC) paradigm for on-chip communication. We demonstrate through the complete implementation of a Monte Carlo-based image reconstruction algorithm for Single-Photon Emission Computed Tomography (SPECT) imaging that this complex problem can be accelerated by two orders of magnitude on even a modestly-sized FPGA over a 2GHz Intel Core 2 Duo Processor. Futhermore, we have created a framework for further increasing paral- lelism by scaling our architecture across multiple compute devices and by extending our original design to a multi-FPGA system nearly linear increase in acceleration with logic resources was achieved.</p> / Master of Applied Science (MASc)

Traditionally, medical imaging techniques such as PET (positron emission tomography) and SPECT (single-photon emission computed tomography) have relied on mechanical collimators to detect the sources of photons. This limits the image's resolution and field of view. To improve upon this, Compton cameras have emerged as a promising alternative. The principle is to measure the angle of a photon scattered in the detector, which indicates the likely sources in the form of a cone culminating in the position of the interaction. The cones from multiple events may be superimposed in order to generate an image. The object of this work is to use list-mode likelihood methods to better reconstruct the source image from the data recorded by a simulated Compton camera in the case of a solid detector volume with good spatial- and energy resolution.  The results demonstrate an improvement of image quality for reconstructions of single point source and multiple extended sources. In addition, the results indicate that our used algorithm converges for point sources. The minimum number of measured events for accurate reconstruction for different source distributions remains to be determined, and the algorithm's ability to resolve closely adjacent sources should be investigated more.

Ce texte de mémoire est accompagné du webdocumentaire interactif : De la chaise à la mer, disponible à l'adresse http://www.delachaisealamer.net. / Ce mémoire de recherche et création étudie le rôle du cinéaste dans la mise en forme de documentaires interactifs diffusés sur le Web. L’auteur se réfère d’abord à ses propres documentaires conventionnels afin d’en définir le principal objectif énonciateur. Puis, il observe les nouvelles positions de spectature favorisées par les dispositifs actuels de distribution médiatique pour comprendre la forme à donner à l’œuvre interactive qu’il est à produire et juger de la possibilité d’y inscrire ses intentions de communication habituelles. L'auteur se réfère par la suite aux documentaires interactifs auxquels il a participé dans les années 1990 et détermine les dispositifs d’interaction permettant une présence active du spectateur. Finalement, l’auteur explique les étapes de production de son webdocumentaire et souligne les éléments de recherche qui ont guidé sa création. L’auteur conclut avec quelques réflexions concernant le rapport existant entre le créateur d’une œuvre documentaire interactive et le spect-acteur multitâche actuel. / This research-creation dissertation studies the filmmaker’s role in the production of interactive web documentaries. First, the author recalls conventional documentaries he directed in order to indentify their primary discursive objectives. Then, he examines the new spectatorship being defined by current media delivery devices to better understand the shape to be given to the interactive work he’s producing and assess its ability in carrying his usual communication objectives. Subsequently, the author refers to interactive documentaries in which he participated in the 1990s and points out specific interactive devices showing to be efficient in taking into account the active presence of the viewer. Finally, the author describes the making of his web documentary and highlights aspects of his research that guided its production. The author concludes with some remarks regarding his creative process and the relationship existing between the filmmaker creator of an interactive documentary and today’s new multitask spect-actor.

Tomografia computadorizada por emissão de fóton único (SPECT) é uma modalidade da medicina nuclear baseada na medida da distribuição espacial de um radionuclídeo. Esta técnica é amplamente utilizada em cardiologia para avaliar problemas de perfusão miocárdica, relacionados ao fluxo sanguíneo nas artérias coronárias. As imagens SPECT proporcionam melhor separação das regiões do miocárdio e facilitam a localização e a definição dos defeitos de perfusão. Um dos grandes desafios em estudos SPECT é a eficiente apresentação da informação, uma vez que um único estudo pode gerar imagens de centenas de cortes a serem analisados. Para resolver este problema, são utilizados mapas polares (também conhecidos como gráficos Bulls Eye). Mapas polares são construídos a partir de cortes tomográficos do ventrículo esquerdo e apresentam as informações dos exames de forma sumarizada, em uma imagem bidimensional. Essa dissertação apresenta um método para segmentação do ventrículo esquerdo em estudos SPECT do miocárdio e a construção de mapas polares. A segmentação do ventrículo esquerdo é realizada para facilitar o processo de geração automática de mapas polares. O método desenvolvido utiliza a transformada watershed, no contexto do paradigma de Beucher-Meyer. Para visualização dos resultados, foi desenvolvida uma aplicação, chamada Medical Image Visualizer (MIV). O MIV será disponibilizado como projeto Open Source, podendo ser livremente utilizado e/ou modificado pela comunidade de usuários, desenvolvedores e pesquisadores. / Single photon emission computed tomography (SPECT) is a nuclear medicine tomographic imaging technique based on the measurement of spatial distribution of a radionuclide. This technique is widely used in cardiology to assess myocardial perfusion problems related to blood flow in coronary arteries. SPECT images provide better separation of regions of the myocardium and facilitate the location and definition of perfusion defects. One of the major challenges in SPECT studies is the efficient presentation of information, since a single study can generate hundreds of images of slices to be analyzed. To address this issue, polar maps (also known as Bulls Eye display) are used. Polar maps are built from slices of the left ventricle and provide summarized information of exams in a two dimensional image. This dissertation presents a method for the segmentation of the left ventricle in myocardial SPECT studies and the construction of polar maps. The segmentation of the left ventricle is performed to facilitate the process of automatic generation of polar maps. The method uses the watershed transform, in the context of the Beucher-Meyer paradigm. To display the results, it was developed an application called Medical Image Visualizer (MIV). MIV will be available as an Open Source project and the communities of users, developers and researchers will be able to freely use and/or modify the application.

L’objectif principal de ce travail est de caractériser par une approche multimodale d’imagerie les bases neurales structurales et fonctionnelles qui sous-tendent les troubles cognitifs et la QV dans la schizophrénie. L’objectif secondaire est de tester la valeur prédictive des troubles cognitifs et de la QV pour l’évolution et le fonctionnement dans la schizophrénie.Nous avons d’abord exploré les profils d’activation cérébrale au cours d’une tâche de mémoire de travail entre des patients qui ont une courte durée d’évolution de la maladie et ceux qui ont une longue durée d’évolution de la maladie. Nous avons retrouvé une hyper activation de certaines régions cérébrales chez les patients avec un longue durée d’évolution de la maladie comparativement aux patients avec une courte durée d’évolution. Nous avons ensuite étudié les bases neurales structurales de la QV. Nous avons mis en évidence qu’une QV altérée était associée à des changements plus importants de la microstructure cérébrale dans des régions altérées par le processus pathologique de la schizophrénie. Nous avons enfin étudié les réseaux cérébraux fonctionnels qui sous-tendent la QV. Nous rapportons que des régions cérébrales impliquées dans la prise de décision, dans le traitement des émotions et dans les cognitions sociales sont liées aux dimensions de la QV.D’une part nos travaux suggèrent qu’une réorganisation fonctionnelle dans le réseau cérébral de la mémoire de travail joue un rôle compensateur lors de l’évolution de la schizophrénie. D’autre part, nos résultats laissent supposer que la QV serait l’expression précoce des anomalies cérébrales induites par les processus pathologiques de la schizophrénie. / We conducted a multimodal neuroimaging approach combining the study of working memory activation with fMRI, the study of microstructural abnormalities associated with impaired QoL using MTI and the study of the functional brain substrate of QoL using SPECT. We aimed to characterize structural and functional neural basis of cognitive impairment and QoL in schizophrenia. We secondarily aimed to test the predictive value of cognitive impairment and QOL for the evolution and functioning in schizophrenia.First, we explored brain activation during a working memory task between patients with short disease duration and patients with long disease duration. We found a functional reorganization in patients with long schizophrenia duration having brain hyperactivations relative to short schizophrenia duration patients. Secondly, we investigated and compared microstructural abnormalities in patients with preserved Qol and impaired QoL. We showed that patients with impaired QoL had more microstructural changes in brain regions affected by the disease process of schizophrenia.Finally, we studied the neural substrate of QoL in schizophrenia. We reported that brain regions involved in cognitions, emotional information processing and social cognition underlie the different QoL dimensions in schizophrenia. On the one hand, our findings suggest that a functional reorganization in the working memory neural network plays a compensatory role in the schizophrenia course. On the other hand, our results suggest that QoL could be the early expression of brain abnormalities induced by the disease process of schizophrenia.

Tomografia computadorizada por emissão de fóton único (SPECT) é uma modalidade da medicina nuclear baseada na medida da distribuição espacial de um radionuclídeo. Esta técnica é amplamente utilizada em cardiologia para avaliar problemas de perfusão miocárdica, relacionados ao fluxo sanguíneo nas artérias coronárias. As imagens SPECT proporcionam melhor separação das regiões do miocárdio e facilitam a localização e a definição dos defeitos de perfusão. Um dos grandes desafios em estudos SPECT é a eficiente apresentação da informação, uma vez que um único estudo pode gerar imagens de centenas de cortes a serem analisados. Para resolver este problema, são utilizados mapas polares (também conhecidos como gráficos Bulls Eye). Mapas polares são construídos a partir de cortes tomográficos do ventrículo esquerdo e apresentam as informações dos exames de forma sumarizada, em uma imagem bidimensional. Essa dissertação apresenta um método para segmentação do ventrículo esquerdo em estudos SPECT do miocárdio e a construção de mapas polares. A segmentação do ventrículo esquerdo é realizada para facilitar o processo de geração automática de mapas polares. O método desenvolvido utiliza a transformada watershed, no contexto do paradigma de Beucher-Meyer. Para visualização dos resultados, foi desenvolvida uma aplicação, chamada Medical Image Visualizer (MIV). O MIV será disponibilizado como projeto Open Source, podendo ser livremente utilizado e/ou modificado pela comunidade de usuários, desenvolvedores e pesquisadores. / Single photon emission computed tomography (SPECT) is a nuclear medicine tomographic imaging technique based on the measurement of spatial distribution of a radionuclide. This technique is widely used in cardiology to assess myocardial perfusion problems related to blood flow in coronary arteries. SPECT images provide better separation of regions of the myocardium and facilitate the location and definition of perfusion defects. One of the major challenges in SPECT studies is the efficient presentation of information, since a single study can generate hundreds of images of slices to be analyzed. To address this issue, polar maps (also known as Bulls Eye display) are used. Polar maps are built from slices of the left ventricle and provide summarized information of exams in a two dimensional image. This dissertation presents a method for the segmentation of the left ventricle in myocardial SPECT studies and the construction of polar maps. The segmentation of the left ventricle is performed to facilitate the process of automatic generation of polar maps. The method uses the watershed transform, in the context of the Beucher-Meyer paradigm. To display the results, it was developed an application called Medical Image Visualizer (MIV). MIV will be available as an Open Source project and the communities of users, developers and researchers will be able to freely use and/or modify the application.