Dissertations / Theses on the topic 'Phantom energy'

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior<br>O fenômeno do colapso gravitacional e a estrutura de estrelas relativísticas são de grande importância em astrofísica desde a formulação da relatividade geral. Alguns trabalhos mais recentes revelam avanços importantes em nosso entendimento da formação de estruturas como buracos negros e singularidades nuas e do comportamento de fluidos exóticos tais como matéria e energia escura, incluindo aqui os fluidos fantasmas. A complexidade do estudo do colapso gravitacional está relacionada à existência de poucas soluções analíticas disponíveis para este fim. Recentemente, soluções auto-similares das equações de campo de Einstein têm atraído grande atenção, não somente pela possibilidade de serem estudadas analiticamente, simplificando o problema, mas também por sua relevância em astrofísica. Neste trabalho, estudamos o colapso gravitacional do fluido anisotrópico com auto-similaridade do segundo e primeiro tipos em espaços-tempos (2 + 1)-dimensionais, com simetria circular. Impondo as equações de estado pr = 0 e p&#952; = &#969;&#961;, onde &#961; determina a densidade de energia e pr, p&#952; as pressões nas direções radial e tangencial do fluido, mostramos que, para soluções com auto-similaridade do segundo tipo, há duas distintas famílias. Para uma delas, as únicas soluções são as que representam fluido de poeira. Todas as soluções para as equações de campo de Einstein são encontradas e suas propriedades locais e globais são estudadas em detalhes. Algumas delas podem ser interpretadas como um processo de colapso gravitacional, em que singularidades nuas e buracos negros são formados. Para a outra família de soluções, temos um modelo cosmológico, com expansão acelerada, que começa em uma singularidade inicial (t = 0), com todas as condições de energia satisfeitas. Nosso propósito foi investigar o papel da não-homogeneidade na aceleração do fluido. Na intenção de estudar as soluções com auto-similaridade do primeiro tipo, mostramos que existe uma solução que representa um processo de colapso gravitacional, resultando em uma estrutura final de buraco negro ou singularidade nua, que podem ser constituídos de um fluido bem comportado ou fantasma.

Objectifs : L’objectif a été de d’optimiser les protocoles d’acquisition des examens d’angiomammographie double-énergie, d’étudier la faisabilité de l’angiotomosynthèse pour la détection et la caractérisation des tumeurs mammaires, et d’étudier la faisabilité des biopsies stéréotaxiques sous guidage de l’angiomammographie. Méthodes : Une étude d’optimisation des paramètres d’acquisition de l’angiomammographie a été réalisée dans 4 situations cliniques pour lesquelles la qualité diagnostique requise des images de basse énergie et la dose totale délivrée à la patiente ne sont pas identiques. L’optimisation des paramètres d'exposition (anode/filtre, kVp, mAs) des images de basse énergie (BE) et haute énergie (HE) a été réalisée à partir d’une modélisation théorique de la chaîne d’acquisition. Une validation a été effectuée par mesures expérimentales sur des images de fantôme d’inserts d’iode. Nous avons ensuite étudié la technique d’angiotomosynthèse mammaire basée sur une approche double-énergie. Un nouveau fantôme anthropomorphique numérique du sein et de ses lésions, basé sur l’utilisation de primitives géométriques complexes et d’une technique de maillage surfacique, a été amélioré et utilisé pour évaluer les performances de l’angiomammographie optimisée, puis de l’angiotomosynthèse en comparaison à l’angiomammographie. Enfin, nous avons proposé un scénario pour la réalisation d’un examen de stéréotaxie avec injection d’un agent de contraste iodé et étudié la faisabilité de recombinaison d’image de haute et de basse énergie acquises à des temps différents de l’injection.Résultats et conclusion : Les optima des paramètres d’exposition trouvés par simulation avec les valeurs de SDNRpixel et SDNR2pixel /Dosetotale qui en résultent, ont été confirmés expérimentalement. Les valeurs de SDNR par pixel dans les images recombinées sont augmentées pour toutes les indications cliniques en comparaison à celle obtenues avec SenoBright ® (produit commercial de référence). L'impact sur la qualité de l’image de BE, évalué par des expérimentations sur fantôme CDMAM, a montré que les paramètres optimisés fournissent une détection similaire ou acceptable par rapport à la mammographie standard, à l’exception de l'indication de dépistage lorsque l’on considère les objets de très petits diamètres.L’étude de lecture humaine d’images simulées d’un fantôme anthropomorphique du sein incluant le rehaussement glandulaire physiologique et différents modèle tumoraux n’a pas montré d’augmentation significative de sensibilité de détection des acquisition 3D d’angiotomosynthèse comparativement aux acquisitions 2D d’angiomammographie. Les deux paramètres qui influençaient le plus la sensibilité était la concentration en iode des tumeurs et la densité du sein. L’angiomammographie était par ailleurs significativement plus spécifique que l’angiotomosynthèse. Une perspective d’amélioration pour l’angiotomosynthèse pourrait donc être l’utilisation d’algorithmes de reconstruction 3D spécifiques de cette modalité qui minimiseraient le bruit de reconstruction. Le scénario proposé pour la réalisation de biopsies sous guidage de l’angiomammographie, a mis en évidence deux contraintes techniques que sont l’échauffement du tube à rayons X et le surcroit de dose dû à la répétition des paires d’acquisitions en haute et basse énergies. Une des solutions envisagées a été de limiter le nombre d’acquisitions de BE. Notre étude a montré que la recombinaison d’une image HE avec une image BE acquise antérieurement modifiait le SDNR des lésions simulées comparativement à une recombinaison appariée d’images BE et HE acquises au même temps de l’injection. Ces modifications dépendaient du temps du pic de rehaussement maximal et du washout de la lésion<br>Objectives: The purpose was to optimize the exposure parameters of CESM examinations, to assess the feasibility of contrast-enhanced DBT (CE-DBT) for the detection and the characterization of breast tumors, and to assess CESM-guided stereotactic biopsies. Methods: At first, we optimized the CESM exposure parameters in four different clinical applications for which different levels of average glandular dose and different low energy image quality are required. The optimization of exposure parameters (anode/filter, kVp, mAs) for low energy (LE) and high energy (HE) images at different levels of average glandular dose and different ratios between LE and total doses has been conducted using a simulator of the x-ray mammographic image chain. An experimental validation was then performed through phantom experiments. Secondly, we assessed the potential of CE-DBT based on a dual-energy approach. A new mesh-based anthropomorphic breast phantom was improved and used to evaluate the performance of CESM and then to compare CESM and CE-DBT. Finally, we evaluated the technical feasibility of CESM-guided biopsy. After identifying some technical constraints, we assessed the performance of the recombination of LE and HE images acquired at different times after injection, using simulated images of a geometric phantom with uniform texture, and simulated images of an anthropomorphic textured phantom with and without motion artifacts.Results and conclusion : For the four different clinical indications, optima found by simulation, with resulting SDNRpixel and SDNR2pixel/Dosetotal, were confirmed through real acquisition of images on phantoms. Our results indicate that the SDNR per pixel in recombined CESM images increased in all of the four clinical indications compared to recombined images obtained using SenoBright ® (commercial product used as reference). This result suggests the possibility to detect more subtle contrast enhancements and to decrease the number of false negatives found in clinical CESM examinations. The impact of a new dose allocation between LE and HE exposures was also evaluated on LE image quality. Results from CDMAM phantom experiments indicate that optimized parameters provide similar or acceptable detection compared to standard mammography, except for screening indication when considering the very small diameter objects.The human observer study on anthropomorphic phantom images, taking into account tumor and breast parenchyma enhancement, revealed that detection and characterization sensitivity of iodine-enhanced lesions are not statistically different between 2D CESM and 3D CE-DBT. The most influencing parameters for the detectability and the lesion size assessment were the lesion iodine concentration and the breast density. CESM was significantly more specific than CE-DBT. One of the assumptions to explain this result is the presence of higher noise in CE-DBT than in CESM images. A future improvement for CE-DBT could therefore be the design of a specific reconstruction algorithm minimizing reconstructed noise.With respect to CESM-guided biopsy the proposed scenario pointed out two major constraints, one related to the thermal load of the x-ray tube, the second related to the increased dose due to the repetition of LE and HE images. One proposed solution was to limit the number of LE exposures, requiring the possibility to recombined LE and HE images acquired at different injection time points. Our study showed that the recombination of a HE image with a LE image acquired earlier leads to SDNR changes compared to paired recombination. These changes are function of the enhancement time to peak and the washout of the lesion, and had a limited impact on the lesion detectability

This work encompasses the study of energy dispersive X-ray diffraction CT (EDXRDCT) system to be installed outside breast tissue biopsy subtraction operation theatre. The system was tested using different materials that simulate breast tissue diffraction pattern contrast and shape compactness. The system spatial resolution was assessed to detect the smallest possible details in each position. The system detection of detail shapes was calculated using compactness parameter. Initially the EDXRDCT system was used with a pinhole CdTe detector to radiate samples of raw materials and different combinations of materials were counted to simulate the contrast between breast tissue at 1.1 nm- i and 1.6 nm- i . The system was then tested using cylindrical samples of two materials with different details sizes (2 mm, 1 mm and O.5mm) that simulate the contrast between breast tissues. Profiles of the EDXRDCT images were plotted and found that details until 1 mm of size can be detected. Some samples of different shapes and materials that simulate breast tissue was scanned using the EDXRDCT system with HEXITEC detector. Scanned parameters were optimised for the beast compactness results that give close values to MicroCT findings. Furthermore a waxed real tissue of liver was scanned to prove the feasibility of scanning waxed tissue instead of fresh ones. The compactness and diffraction of sample details was measured. Finally, a phantom that simulates breast tissue contrast and shapes was designed to test the EDXRDCT system with HEXITEC detector. The system was capable to show details shape and give close compactness values to Micro CT results in 2.5 hours scanning time.

This thesis presents work around 3 themes: dark energy, gravitational waves and Bayesian inference. Both dark energy and gravitational wave physics are not yet well constrained. They present interesting challenges for Bayesian inference, which attempts to quantify our knowledge of the universe given our astrophysical data. A dark energy equation of state reconstruction analysis finds that the data favours the vacuum dark energy equation of state $w {=} -1$ model. Deviations from vacuum dark energy are shown to favour the super-negative ‘phantom’ dark energy regime of $w {< } -1$, but at low statistical significance. The constraining power of various datasets is quantified, finding that data constraints peak around redshift $z = 0.2$ due to baryonic acoustic oscillation and supernovae data constraints, whilst cosmic microwave background radiation and Lyman-$\alpha$ forest constraints are less significant. Specific models with a conformal time symmetry in the Friedmann equation and with an additional dark energy component are tested and shown to be competitive to the vacuum dark energy model by Bayesian model selection analysis: that they are not ruled out is believed to be largely due to poor data quality for deciding between existing models. Recent detections of gravitational waves by the LIGO collaboration enable the first gravitational wave tests of general relativity. An existing test in the literature is used and sped up significantly by a novel method developed in this thesis. The test computes posterior odds ratios, and the new method is shown to compute these accurately and efficiently. Compared to computing evidences, the method presented provides an approximate 100 times reduction in the number of likelihood calculations required to compute evidences at a given accuracy. Further testing may identify a significant advance in Bayesian model selection using nested sampling, as the method is completely general and straightforward to implement. We note that efficiency gains are not guaranteed and may be problem specific: further research is needed.

CNPq; CAPES<br>A termografia permite a visualização de valores de temperatura de um corpo por meio de imagens. Na área médica, encontra aplicações em oncologia, análise de queimaduras, doenças vasculares, doenças respiratórias, doenças de pele e como forma geral de verificação da vitalidade dos tecidos. A termografia 3D consiste de uma malha 3D com uma textura térmica projetada em sua superfície, oferecendo uma visualização mais precisa dos padrões de temperatura das estruturas anatômicas. Propõe-se, por meio do presente trabalho, um sistema capaz de combinar imagens termográficas 2D com sua malha 3D correspondente e, como resultado, entregar uma imagem termográfica 3D para aplicações médicas. Para isso foram utilizadas as técnicas de Otimização por Enxame de Partículas (PSO) e de reconstrução 3D Structure from Motion (SfM). Diferentemente de outros trabalhos na literatura, a malha 3D e as imagens térmicas não precisam ser adquiridas simultaneamente, não sendo necessário um arranjo mecânico dedicado. A malha 3D pode ter origem em um scanner 3D ou em uma imagem de ressonância magnética, por exemplo. Para avaliar os resultados, um phantom, isto é, um objeto estático de avaliação, com propriedades conhecidas, foi construído. Para tal, uma técnica inédita, utilizando placas de circuito impresso foi desenvolvida. Como resultado, comparações entre a saída do método proposto e o phantom, apresentaram um erro máximo de 3,73 mm e médio de 1,41 mm, com desvio padrão de 0,74 mm, em um phantom de 100 x 150 x 103,2 mm.<br>Thermography is an imaging method that allows temperature visualization of various regions of an object. In medicine, it finds applications related to oncology, burn trauma, vascular, respiratory and skin diseases, and as a general tissue vitality checking tool. 3D thermography adds tridimensional information to the conventional 2D thermography. It is made from a 3D mesh wrapped by thermal texture, enabling a more precise visualization of thermal patterns of anatomical structures. We propose a system capable of combining 2D thermal images with their corresponding 3D mesh, delivering a 3D thermogram for medical applications as a result. We used Particle Swarm Optimization (PSO) for mesh alignment and Structure from Motion (SfM) for 3D reconstruction in the present method. In contrast to most research found in the literature, the 3D mesh and the thermal images do not need to be acquired simultaneously, and a mechanical support for the thermal camera and the 3D scanner is not required. The 3D mesh may be acquired, for instance, from a 3D scanner or a magnetic resonance imaging machine. In order to evaluate the results, a phantom, that is, a static assessment object of known properties has been built. For this purpose, a novel technique using printed circuit boards has been developed. As a result, comparison between the output of the method and the phantom shows a maximum error of 3.73 mm and a mean error of 1.41 mm with 0.74 mm of standard deviation in phantom of 100 x 150 x 103.2 mm.<br>5000

A terapia com prótons está presente em 16 países e até 2015 tratou mais de 130 mil pacientes. No entanto, no Brasil essa terapia ainda não está presente por diversos motivos, sendo o principal o alto custo. Antes de realizar tratamentos, é necessário fazer alguns testes para verificação da entrega de energia dos feixes de prótons. Como as medidas de microdosimetria são muito caras, a principal alternativa é a realização de simulações em programas computacionais, como o GEANT4 e SRIM. O GEANT4 é um programa que permite simular geometrias complexas, enquanto que o SRIM realiza simulações mais simples e ambas trabalham com o método de Monte Carlo. Neste trabalho foram utilizadas estas duas ferramentas para realizar simulações de feixes de prótons em fantomas com três diferentes composições (água, água e tecido ósseo, tecido ósseo e cerebral). Para realizar a análise da entrega de energia dos feixes de prótons ao longo destes fantomas, tornou-se necessário criar um programa denominada “Programa de Processamento de Dados em Próton Terapia Simulada”, que proporcionou criar matrizes, além dos cálculos dos picos de Bragg para avaliação da interação. Além disso, foi analisada a homogeneidade da interação de um feixe de prótons em um detector, em que foi verificado que as simulações em GEANT4 são homogêneas, não tendo uma tendência do feixe em se localizar em uma determinada região, assim como as energias depositadas são iguais nas regiões do fantoma. Também foram avaliados os valores do alcance de profundidade dos picos de Bragg em fantomas cilíndricos com três diferentes densidades: 1,03 g/cm³, 1,53 g/cm³ e 2,03 g/cm³, sendo a primeira, a densidade fornecida pelo GEANT4 para tecido cerebral. Foi verificado que as distâncias do alcance de profundidade dos picos de Bragg são iguais nestas três diferentes densidades.<br>Proton therapy is present in 16 countries and by 2015 has treated more than 130,000 Patients. However, in Brazil this therapy is not yet present for several reasons, Being the main the high cost. Before performing treatments, it is necessary to do some tests to verify the energy delivery of the proton bundles. As the Microdosimetry are very expensive, the main alternative is to carry out simulations in Programs such as GEANT4 and SRIM. GEANT4 is a program that Allows you to simulate complex geometries, while SRIM performs more complex simulations. Simple and both work with the Monte Carlo method. On this work were used these twain tools to perform a proton beam simulation in phantom with three different compositions (water, bones and water, brain and bones). To perform the energy delivery analysis of the proton beams along these phantoms, has become necessary create a program denominated “Data Processing Program Proton Therapy Simulated”, which allowed to create matrices, beyond the calculations of the Bragg peaks for interaction evaluation. Besides that, it was analyzing the homogeneity of the integration of a proton beam into a detector, in which it was verified that the simulations on GEANT4 are homogeneous, not having a tendency of the beam in locating in a certain region, just as the energies deposited are equal. The value of the depth range of the Bragg peaks were also evaluated in cylindrical phantoms with three different densities: 1,03 g/cm³, 1,53g/cm³ and 2,03 g/cm³, the first being the density provided by GEANT4 for brain tissue. It has been found that the depth range distances of the Bragg peaks are the same at these three different densities.

Multi-tier heterogeneous networks have become an essential constituent for next generation cellular networks. Meanwhile, energy efficiency (EE) has been considered a critical design criterion along with the traditional spectral efficiency (SE) metric. In this context, we study power and spectrum allocation for the recently proposed two-tier network architecture known as phantom cellular networks. The optimization framework includes both EE and SE. First, we consider sparsely deployed cells experiencing negligible interference and assume perfect channel state information (CSI). For this setting, we propose an algorithm that finds the SE and EE resource allocation strategies. Then, we compare the performance of both design strategies versus number of users, and phantom cells share of the total available resource units (RUs). We aim to investigate the effect of some system parameters to achieve improved SE performance at a non-significant loss in EE performance, or vice versa. It is found that increasing phantom cells share of RUs decreases the SE performance loss due to EE optimization when compared with the optimized SE performance. Second, we consider the densely deployed phantom cellular networks and model the EE optimization problem having into consideration the inevitable interference and imperfect channel estimation. To this end, we propose three resource allocation strategies aiming at optimizing the EE performance metric of this network. Furthermore, we investigate the effect of changing some of the system parameters on the performance of the proposed strategies, such as phantom cells share of RUs, number of deployed phantom cells within a macro cell coverage, number of pilots and the maximum power available for transmission by the phantom cells BSs. It is found that increasing the number of pilots deteriorates the EE performance of the whole setup, while increasing maximum power available for phantom cells transmissions reduces the EE of the whole setup in a less severe way than increasing the number of pilots. It is found also that increasing phantom cells share increases the EE metric in the dense deployment case. Thus, it is always useful to allocate most of the network RUs to the phantom cells tier.

碩士<br>國立臺灣大學<br>物理研究所<br>100<br>In 1998, two groups studying supernovae have made a Nobel-Prize discovery, that the universe is under accelerating expansion. This suggests a substance, called dark energy, with strong negative pressure required to explain the acceleration. Numeral models have been proposed in order to explain the nature of dark energy, and they have to be tested with observations. Apart from ΛCDM, one type of promising dark energy candidate is scalar-field dark energy. Some of the scalar-field dark energy have attractor property that can alleviate cosmic coincidence problem. Quintessence and phantom are both scalar- field dark energy, with w > −1 and w < −1, respectively. This thesis is a work on confronting scalar-field dark energy models with current observations. The models we have considered are tracker quintessence and attractor/tracker phantom with several po- tential forms, which are all insensitive to initial conditions. While observation data come from latest SNIa, CMB and BAO, we obtain the best-fit and constraints on parameters for each model, showing that current observations limit dynamical behavior. By assess- ing Goodness-of-Fit and information criteria of models, it shows that ΛCDM is still the most preferred. Furthermore, current data favors phantom with w < −1 than quintessence with w > −1.

碩士<br>義守大學<br>生物醫學工程學系<br>105<br>Dual energy computed tomography (DECT) has grown rapidly in the last decade. It is widely applied in clinical applications, commonly on brain and cardiovascular angiography, blood perfusion angiography, carotid artery, pediatric non-sedative ultra-fast CT scan and discriminates different high-brightness substances, including soft and hard vascular wall plaques, contrast agents and calculus and gout of calcified substances. In order to ensure the image quality of computed tomography examination in our country. Annual quality assurance (QA) test of computed tomography scanner should be carried out to guarantee the system status, which is required and specified by Atomic Energy Council (AEC). One of the most important X-ray computed tomography QA test tools is ACR Phantom which is a phantom certified by American College of Radiography Phantom. The current definition form AEC is only for single-energy computer tomography. The present specification demands on single energy CT (SECT) scanner. In this study, we compared the SECT and DECT using the same scanning parameters to perform scanning on ACR phantom and to reconstruct CT images. In the meantime, it was proposed to investigate the changes of image features on the ACR Phantom’s Module1, Module2, Module3 and Module4 by shifting phantom’s position individually. The results showed that the measurements of SECT scan were more reliable because smaller deviations for all of the modules’ measurements (CT number, low contrast resolution, in-plane distance accuracy or high contrast resolution) which were within the range of Atomic Energy Council (AEC) specification. However, excluding the measurement of module 3, the measurements of the other three modules had large variations by DECT scan. And there had similar variations with SECT measurements for all three measurements under some specific conditions using DECT scan.

碩士<br>中原大學<br>生物醫學工程研究所<br>103<br>The purpose of this study evaluated the bone mineral density (BMD) values of a phantom in different models of bone densitometer of a particular brand, and difference estimated. In this study, the N series densitometers were applied to evaluate the BMD of a lumbar phantom. The N brand XR 600 was used to scan the lumbar phantom for 15 times and calibrated, and the data used as standard. The imitations were repeated under the same condition using other series of N. According The SigmaPlot v.12.5 was used to analyze collected data. Difference between standardized phantom BMD and other imitated BMD values was analyzed using one way ANOVA. The p value of bone density, bone content and bone area were less than 0.01, 0.01 and 0.05, respectively. The average of BMD values of different modalities was analyzed by Results (% True) of measurements, and homogeneity of BMD values was indicated. Therefore, no obvious deviation was observed under different modalities, and the results of examinations may be used in relevant research.

碩士<br>中原大學<br>生物醫學工程研究所<br>99<br>Abstract The purpose of this research is to investigate the capability of detecting slight bone mineral density value changes of those dual-emission X-ray absorptiometries used in clinical. This experiment is designed based on the combination of clinical experiences and academic research method to demonstrate the sensitivity of those dual-emission X-ray absorptiometries widely used in clinical. In this research, a standard phantom is produced based on the different X-ray attenuation factors of Aluminum and acrylics and a standard scan pattern is also established. The values generated from the phantom scanned by clinical used absorptiometries under standard scan pattern are analyzed and compared. The experiment is comprised of standard phantom production, the investigation of quality assurance and quality control results of each absorptiometry, comparison of detected radiation dose, data analysis and recognition of realistic and arithmetic values. According to the data from this research, the factors, which might affect the capability of absorptiometry of detecting slight bone mineral density value changes, such as, scan model, thickness of body and the patient information changes are discussed. The result of this experiment will be used as the reference of absorptiometry quality investigation. Key word: Dual-emission X-ray absorptiometry, Accuracy, Precision, realistic value, arithmetic value.

碩士<br>中山醫學大學<br>生物醫學科學學系碩士班<br>100<br>The traditional spiral scans of computer tomography using a single energy, and recently the Siemens CT using dual-energy scanning protocol apply to arterial phase scan of liver triple-phase examination, and improve the diagnosis rate of the lesion. The Toshiba CT has a 320-row detector, the lap maximum scan range of up to 16 cm, can be an extension of the wide volume scan. The study use Siemens CT and Toshiba CT to evaluate the effective dose of the liver triple-phase examination. In image quality evaluation, the study use the dual energy mode of Siemens CT and the wide-volume mode of Toshiba CT to scan Catphan phantom and reconstruct image by FBP and IR mode to compare their traditional spiral scan mode. The Rando phantom filled with TLDs to evaluate dose in the liver triple-phase examination. In addition, the experiment also used a single topogram scan protocol to assess the doses of the liver triple-phase examination. The Catphan phantom with self-made body annulus phantom was scanned by the AEC system and the 12 manual dose modes to evaluate the image quality of the four scan mode. In clinical examinations of the liver triple-phase, the lowest effective dose is in Siemens CT, the next is the wide-volume mode of Toshiba CT and the helical mode of Toshiba CT. In the FOMCNR of AEC mode reconstructed by FBP method, the best of FOMCNR is the dual energy scan mode of Siemens CT, and the next is the helical mode of Toshiba CT. If we use the IR mode of image reconstructions, the best of FOMCNR is also the dual energy scan mode of Siemens CT, and the next is the single energy scan mode of Siemens CT and the wide-volume mode of Toshiba CT.

abstract: Coronary computed tomography angiography (CTA) has a high negative predictive value for ruling out coronary artery disease with non-invasive evaluation of the coronary arteries. My work has attempted to provide metrics that could increase the positive predictive value of coronary CTA through the use of dual energy CTA imaging. After developing an algorithm for obtaining calcium scores from a CTA exam, a dual energy CTA exam was performed on patients at dose levels equivalent to levels for single energy CTA with a calcium scoring exam. Calcium Agatston scores obtained from the dual energy CTA exam were within ±11% of scores obtained with conventional calcium scoring exams. In the presence of highly attenuating coronary calcium plaques, the virtual non-calcium images obtained with dual energy CTA were able to successfully measure percent coronary stenosis within 5% of known stenosis values, which is not possible with single energy CTA images due to the presence of the calcium blooming artifact. After fabricating an anthropomorphic beating heart phantom with coronary plaques, characterization of soft plaque vulnerability to rupture or erosion was demonstrated with measurements of the distance from soft plaque to aortic ostium, percent stenosis, and percent lipid volume in soft plaque. A classification model was developed, with training data from the beating heart phantom and plaques, which utilized support vector machines to classify coronary soft plaque pixels as lipid or fibrous. Lipid versus fibrous classification with single energy CTA images exhibited a 17% error while dual energy CTA images in the classification model developed here only exhibited a 4% error. Combining the calcium blooming correction and the percent lipid volume methods developed in this work will provide physicians with metrics for increasing the positive predictive value of coronary CTA as well as expanding the use of coronary CTA to patients with highly attenuating calcium plaques.<br>Dissertation/Thesis<br>Ph.D. Bioengineering 2013