Thesis (M.S.)--University of Michigan, 1979.

Thesis (M.S.)--University of Michigan, 1979.

Thesis (M.S.)--University of Michigan, 1985.

Thesis (M.S.)--University of Michigan, 1985.

A feasibility study into the use of UHF-EM transillumination measurements in geophysics is presented. The electrical properties and absorption rates of common crustal materials are examined with the goal of identifying specific conditions under which sufficient material penetration at UHF frequencies is available. / A prototype 445 MHz continuous-wave transillumination instrument designed for underground use is described. Test surveys, with this instrument, were conducted at the Big Nickel Mine in Sudbury, Ontario, to obtain a number of through-rock absorption rates. Estimated effective resistivities of between 500 and 1500 ohm-metres are determined from the survey data. / Effective conductivities and permittivities from AC and DC electrical property measurements on geological samples from the mine site corroborate these transillumination survey results. / The results of the field surveys indicate that the UHF-EM transillumination technique is a feasible and useful geophysical method.

No description available.

Breast transillumination has received renewed interest as a noninvasive diagnostic method. However, it is still considered an experimental technique. Many aspects of the physics involved in transillumination have not yet been studied. In this project transillumination was simulated by experiments with a simple breast phantom of realistic dimensions. The light source used was a HeNe laser. From the experiments we found how the contrast of images of a spherical inhomogeneity (simulating a lesion e.g. tumor or cyst) depended on its size and position. The contrast was also measured as a function of the scattering and absorption coefficients of the inhomogeneity. The contrast of the image is shown to fit very well to the curve A(1-exp(-d(Σ^inh_eff – Σ_eff))), where a simple analytical model is developed, where A is identified to (1+B)^-1, B being a build-up factor depending on the surrounding medium and on the position of the inhomogeneity in the medium and d is identified as an effective optical diameter of the inhomogeneity. A three dimensional numerical diffusion program was developed to model the transillumination situation. It was found that diffusion theory gave accurate predictions of the contrast within the constraints of the mathematical model. The three dimensional diffusion approximation and its limitations are discussed in some detail. / Thesis / Master of Science (MSc)

Cracked teeth may be difficult to diagnose. Craze lines rarely become symptomatic or require treatment. Cracks in the enamel and dentin alone may or may not become symptomatic and require restorative treatment. However, cracks extending into the enamel, dentin, and pulp chamber provide an avenue for bacteria to establish infection and this commonly results in symptoms and the need for endodontic and restorative treatment. The published endodontic literature has limited information regarding the prevalence or predictive factors for cracks extending into the pulp chamber of teeth. The purpose of this study was to determine the prevalence and classification of intrapulpal cracks in maxillary premolars and to identify factors that may aid in diagnosing the existence and extent of a crack. The cracks were classified according to the Intrapulpal Crack Classification System proposed by Detar in 2014. All maxillary premolar teeth treatment planned for non-surgical root canal therapy (NSRCT) or retreatment (RETX) at Virginia Commonwealth University (VCU) Graduate Endodontic Practice from January 2014 through February 2015 were included in the study after obtaining patient consent. Teeth were examined visually, stained, and examined microscopically for the presence of an intrapulpal crack. Demographic information, subjective data associated with the chief complaint, objective results of diagnostic testing (percussion, palpation, bite stick test, transillumination, probing depths), existing restorations, pulpal diagnosis, and periapical diagnosis were analyzed using chi-square and multiple logistic regression (P

A proposta desse trabalho é demonstrar a viabilidade da técnica de transiluminação com a captação de imagens digitais através de uma pastilha de resina com pinos metálicos posicionados sobre sua superfície e imagens geradas a partir de elementos dentais, também, foram realizados processamentos matemáticos com base na transformada rápida de Fourier. Para a geração das imagens foram utilizadas fontes de laser e led com comprimentos de onda que vão do visível ao infravermelho. A análise das imagens mostrou que imagens formadas com led foram superiores as imagens formadas com laser e a cor azul não apresentou contraste suficiente independente da fonte de iluminação. Os resultados mostraram que o uso de Lasers não obteve sucesso devido à difração da luz pelos pinos e à interferência entre as radiações laser, o que provocou imagens com baixa resolução. No entanto, usando a fonte de led, foi possível definir a morfologia dos pinos na resina. Como conclusão verificou-se que os efeitos ópticos de absorção e espalhamento da luz pela resina e pelo dente, a difração da luz pelos pinos e a interferência da luz coerente foram os fatores de maior influência para a análise das imagens. / The propose of this work is to demonstrate the feasibility of the technique of transillumination to capture digital images through a resin with metal pins placed on its surface and images generated from dental elements. In addition has been made on the basis of mathematical processing transformed rapidly from Fourier. For the generation of images were used sources of laser and led with a wavelength ranging from visible to infrared. The analysis of the images showed that images formed with higher led the images were formed with laser and the blue not presented sufficient contrast independent of the source of illumination. The results showed that the use of Lasers not succeeded because of diffraction of light by pins and the interference between the laser radiation, which caused images with low resolution. However, using the source of led, it was possible to define the morphology of pins in the resin. In conclusion we note that the effects of optical absorption and scattering of light by the resin and the tooth, the diffraction of light by pins and interference of light were consistent factors of greater influence for the analysis of images.

A proposta desse trabalho é demonstrar a viabilidade da técnica de transiluminação com a captação de imagens digitais através de uma pastilha de resina com pinos metálicos posicionados sobre sua superfície e imagens geradas a partir de elementos dentais, também, foram realizados processamentos matemáticos com base na transformada rápida de Fourier. Para a geração das imagens foram utilizadas fontes de laser e led com comprimentos de onda que vão do visível ao infravermelho. A análise das imagens mostrou que imagens formadas com led foram superiores as imagens formadas com laser e a cor azul não apresentou contraste suficiente independente da fonte de iluminação. Os resultados mostraram que o uso de Lasers não obteve sucesso devido à difração da luz pelos pinos e à interferência entre as radiações laser, o que provocou imagens com baixa resolução. No entanto, usando a fonte de led, foi possível definir a morfologia dos pinos na resina. Como conclusão verificou-se que os efeitos ópticos de absorção e espalhamento da luz pela resina e pelo dente, a difração da luz pelos pinos e a interferência da luz coerente foram os fatores de maior influência para a análise das imagens. / The propose of this work is to demonstrate the feasibility of the technique of transillumination to capture digital images through a resin with metal pins placed on its surface and images generated from dental elements. In addition has been made on the basis of mathematical processing transformed rapidly from Fourier. For the generation of images were used sources of laser and led with a wavelength ranging from visible to infrared. The analysis of the images showed that images formed with higher led the images were formed with laser and the blue not presented sufficient contrast independent of the source of illumination. The results showed that the use of Lasers not succeeded because of diffraction of light by pins and the interference between the laser radiation, which caused images with low resolution. However, using the source of led, it was possible to define the morphology of pins in the resin. In conclusion we note that the effects of optical absorption and scattering of light by the resin and the tooth, the diffraction of light by pins and interference of light were consistent factors of greater influence for the analysis of images.