Thesis (Ph. D.)--University of Texas at Austin, 2005. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Idaho, 2005. / Abstract. "December, 2005." Includes bibliographical references. Also available online in PDF format.

Thesis (Ph. D.)--University of Texas at Austin, 2005. / Supervisor: Thomas E. Milner. Vita. Includes bibliographical references.

In Electrical Impedance Tomography the conductivity of an object is estimated from boundary measurements. An array of electrodes is attached to the surface of the object and current stimuli are applied via these electrodes. The resulting volt ages are measured. The process of estimating the conductivity as a function of space inside the object from voltage measurements at the surface is called reconstruction. Mathematically the ElT reconstruction is a non linear inverse problem, the stable solution of which requires regularisation nwthods. Most common regularisation methods impose that the reconstructed image should be smooth. Such methods confer stability to the reconstruction process, but limit the capability of describing sharp variations in the sought parameter. In this thesis two new methods of regularisation are proposed. The first method, Gallssian anisotropic regularisation, enhances the reconstruction of sharp conductivity changes occurring at the interface between a contrasting object and the background. As such changes are step changes, reconstruction with traditional smoothing regularisation techniques is unsatisfactory. The Gaussian anisotropic filtering works by incorporating prior structural information. The approximate knowledge of the shapes of contrasts allows us to relax the smoothness in the direction normal to the expected boundary. The construction of Gaussian regularisation filters that express such directional properties on the basis of the structural information is discussed, and the results of numerical experiments are analysed. The method gives good results when the actual conductivity distribution is in accordance with the prior information. When the conductivity distribution violates the prior information the method is still capable of properly locating the regions of contrast. The second part of the thesis is concerned with regularisation via the total variation functional. This functional allows the reconstruction of discontinuous parameters. The properties of the functional are briefly introduced, and an application in inverse problems in image denoising is shown. As the functional is non-differentiable, numerical difficulties are encountered in its use. The aim is therefore to propose an efficient numerical implementation for application in ElT. Several well known optimisation methods arc analysed, as possible candidates, by theoretical considerations and by numerical experiments. Such methods are shown to be inefficient. The application of recent optimisation methods called primal- dual interior point methods is analysed be theoretical considerations and by numerical experiments, and an efficient and stable algorithm is developed. Numerical experiments demonstrate the capability of the algorithm in reconstructing sharp conductivity profiles.

Global assessment of myocardial function is widely performed by estimating ejection fraction (EF), but many common cardiac diseases initially affect the myocardium on a regional, rather than global, basis. Computed tomography (CT), most commonly applied to assess the coronary arteries, is a prime candidate for such regional analysis. This doctoral thesis makes steps towards regional CT functional analysis with two clinical and two technical contributions. The first clinical contribution focuses on evaluating the feasibility and utility of functional analysis with currently available CT technology. Our study found that CT strain analysis could identify regional wall motion abnormalities in cardiomyopathy that are not otherwise detected using conventional metrics of myocardial function such as EF. In order for cine CT of the heart to become routine clinical practice, improvements need to be made to the image acquisition protocol. The second clinical contribution focus on making these improvements with results pointing to the possibility of one millisievert range cine CT images with high (>50 milliseconds) temporal resolutions. Moving to technical considerations, a key concern has been how to better characterise the myocardium in CT. To address this, the first technical contribution examines the use of feature-based attribute vectors, which were found to improve image registration towards deriving more reliable motion estimations. The second technical contribution focus on developing a pipeline tailored towards CT strain analysis. Noting that CT naturally provides information in 3D, a 3D hyperelastic biomechanical model fitting method was evaluated. Analysis of an infarction model demonstrated that regional myocardial strain can be estimated in the 3D space and areas of infarction can be detected. By considering both technical and clinical perspectives, these advances will contribute to the the field of regional cardiac functional analysis towards improving patient care.

Orientadores: José Flávio Affonso de Almeida, Maria Cristina Volpato / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-17T16:39:58Z (GMT). No. of bitstreams: 1 Monteiro_MariaRachelFigueiredoPenalva_M.pdf: 1282276 bytes, checksum: b7401c79964f58abbced19c5c4e238eb (MD5) Previous issue date: 2011 / Resumo: Processos inflamatórios com pulpite irreversível podem promover alterações que levam à hiperalgesia e alodínia, tornando mais difícil a obtenção de anestesia local efetiva. Este estudo teve como objetivo avaliar a eficácia anestésica de duas soluções e técnicas anestésicas em molares inferiores com pulpite irreversível, comparando a técnica infiltrativa vestibular mandibular com a solução de articaína 4% (grupo 1) com a técnica de bloqueio dos nervos alveolar inferior e lingual com o uso da lidocaína 2% (grupo 2), ambas associadas à epinefrina 1:100.000. Também foi avaliada a eficácia da técnica inicial mais uma complementação (técnica infiltrativa- articaína com técnica intraligamentar- articaína e, bloqueio- lidocaína com técnica infiltrativa- articaína) entre os grupos e comparadas às eficácias anestésicas da técnica inicial e técnica inicial mais uma complementação no mesmo grupo. Além disso, foi avaliada a relação entre o desempenho da articaína e a espessura da cortical óssea vestibular e a distância das raízes mesial e distal à mesma cortical, por meio de tomografia computadorizada ¿Cone Beam¿. Para tal, foram distribuídos 43 voluntários em 2 grupos experimentais 43 pacientes (28 do grupo 1; 15 do grupo 2) com molares inferiores diagnosticados com pulpite irreversível. Todos foram orientados a preencher escalas analógicas visuais (EAV) para demonstrar a intensidade de dor anteriormente ao tratamento (calibração), durante o exame de diagnóstico clínico (endofrost) e após 5 e 10 minutos da aplicação da anestesia. Foram considerados sucessos os casos tratados sem dor com a técnica inicial e com a técnica inicial mais complementação anestésica. Não foi observada diferença estatisticamente significante (p=0,0955) para a técnica inicial (articaína 4% sucesso de 39,7% e lidocaína 2% sucesso de 13,3%) nem para a técnica inicial mais uma complementação quando comparados os grupos (p=0,7448). No entanto, quando analisado o mesmo grupo, foi encontrada diferença estatisticamente significante para a técnica inicial mais complementação anestésica no grupo da lidocaína (p=0,0025). Em relação à análise tomográfica, não houve influência da espessura da cortical óssea vestibular e da distância entre as raízes mesial e distal até a mesma cortical óssea no desempenho da articaína (p>0,05). Concluiu-se que, a infiltração com articaína obteve desempenho semelhante ao bloqueio com lidocaína pela técnica inicial ou após complementação anestésica e que a espessura da cortical óssea e a distâncias das raízes à cortical óssea não tem relação direta com o sucesso ou insucesso da eficácia anestésica da articaína. / Abstract: Inflammatory process due to irreversible pulpits can cause hyperalgesia and allodynia that can difficult proper profound local anesthesia. The main goal of this study was to evaluate the anesthetic efficacy of two initial techniques and solutions in mandibular molars, one in mandibular infiltrations with 4% articaine (group 1) an alveolar nerve block with 2% lidocaine (group 2), both with 1:100.000 epinephrine. Likewise, evaluated the efficacy of the initial technique and one supplemental injection between groups and inside the same group (mandibular infiltration and intraligamentary infiltration both with articaine and alveolar nerve block with lidocaine and mandibular infiltration with articaine) and the relationship of success and failure of articaine with buccal cortical thicknesses and mesial and distal root distance to the same cortical (cone beam tomography). Data (43 volunteers), admitted with a clinical diagnostic of irreversible pulpits, were randomized into two experimental groups (28 from group 1 and 15 from group 2). All patients were instructed to assess their pain in a visual analogue scale (VAS) before treatment, after cold testing and 5 and 10 minutes after the injection. Success criteria were painless treatment with only an initial anesthesia or adding one supplemental injection. There was no statistic difference between group 1 (39.7%) and group 2 (13.3%) (p=0.0955) with the initial technique and with one supplemental injection when groups were compared (p=0.7448). However, there was statistical difference when analyzed inside the same group for lidocaine (p=0.0025). Yet, no statistical difference was observed in tomography evaluation between articaine efficacy and buccal cortical thickness in mesial and distal root or between articaine efficacy and mesial and distal root distance to the buccal cortical (p>0.05). It was concluded that articaine was similar to lidocaine effectiveness with the initial technique or with one supplemental injection and that the buccal cortical thickness and the mesial and distal root distance to the same cortical had no relationship to the success or failure of articaine efficacy. / Mestrado / Endodontia / Mestre em Clínica Odontológica

Since the first introduction of reconstructive tomography in medicine more than a decade ago, research into this technique has continued to arrest the interest of a growing number of scientists especially in the area of industrial non-destructive testing. It is thus an advantage for a laboratory to have a test rig that combines the various Imaging modalities using ionising radiations. Such a test rig has been designed and built around a BBC-B microcomputer complete with its own display system. It combines the ability for transmission and emission tomography with a capability for Compton scattering imaging. Imaging characteristics of the rig including the detectors efficiency, response, collimating systems line spread functions, resolution and the modulation transfer functions are determined. A model has been established to numerically calculate accurately the scattering volume and predict the scattering field at any scattering angle for bore-hole type of collimation. Images of aluminium phantom with lead and brass inclusions have been used to demonstrate the particular suitability of the Compton scattering technique for detecting dense materials within a low density medium. The use of an attenuation correction method for the scattered photons has proved very successful in improving contrast and signal-to-noise ratio of the images. None of the established imaging methods has proved capable of elemental distribution analysis and the methods used in elemental analysis lack the spatial information provided in imaging. A new and novel method is presented in this work that combines the elemental capability of neutron activation analysis with the spatial information of emission tomography. This method has been termed neutron induced gamma-ray emission tomography (NIGET). NIGET images obtained of a freeze-dried water pellet, a piece of human tibia and a study of the diffusion of a preservative solution in a sample of Scots-pine, have been used to demonstrate the potentials of this method.

No description available.

This work presents an analytic three dimensional image reconstruction algorithm that was developed for a proposed volume-imaging PET scanner. The development of the algorithm was motivated by the scanner's ability to collect an order of magnitude more data than current PET systems and the lack of an efficient algorithm that could use the extra data. The algorithm is based on an extension of the Recovery Operator of Orlov[68] and operates by convolution in object space. This method of operation sets it apart from other analytic direct image reconstruction algorithms that rely on Fourier transforms. The algorithm is tested with ideal data and parameters that are appropriate to the new PET scanner. The results of the test show that the algorithm behaves as expected except for a 17% overshoot in the reconstructed value in one area. An explanation of this artifact is suggested, although not verified. Finally, the efficacy of the algorithm is demonstrated by proving that it is functionally equivalent to Fourier transform methods. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Most downhole tools in use today measure properties immediately adjacent to the borehole, and as such, only a small portion of the subsurface volume is known with any degree of certainty. When dealing with geologic situations which are characteristically heterogeneous, the engineer often requires more information than what present tests can provide. Tomography is an in-situ testing method that allows the generation of a two dimensional subsurface image by reconstructing material property variations between boreholes. It is essentially a solution to the inverse problem where signals are measured and, through computer manipulation, are used to infer material contrasts in the subsurface. For the purposes of this thesis, a two dimensional configuration is used to demonstrate and evaluate the tomographic technique with source and receiver locations positioned at intervals down adjacent and nearly vertical boreholes. Both iterative and direct matrix solution methods are used to evaluate the use of seismic and groundwater flow data for subsurface tomography. The iterative methods include a variation of the classical algebraic reconstruction technique (CART), a modified version of the ART algorithm (MART), and a modified version of the ART algorithm using the Chebyshev norm criterion (LART). The purpose of the iterative tests is to determine the best algorithm for signal reconstruction when data noise and different damping parameters are applied. The matrix methodologies include a constrained L¹ linear approximation algorithm and singular value decomposition routines (SVD). These methods solve the set of linear equations (Ax = b) which the tomographic techniques produce. The purpose of this stage of testing is to optimize a direct method of solution to the sets of linear equations such that different forms of anomaly can be discerned. Numerous synthetic seismic and groundwater data sets are used by both iterative and matrix algorithms. Seismic test data sets are generated by calculation of transit times through materials of known seismic velocity. Groundwater test data sets are generated by drawdown analyses and finite element procedures. All algorithms demonstrate a reasonable ability at reconstructing sections which closely re-sembled the known profiles. Vertical anomalies, however, are not as well defined as horizontal anomalies. This is primarily a result of incomplete cross-hole scanning geometry which also affects the rank and condition of the matrices used by the direct forms of solution. The addition of Gaussian noise to the data produces poor reconstructions regardless of the type of algorithm used. This emphasizes the fact that tomographic techniques require clear and relatively error-free signals. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate