Metodologia para a digitalização de radiografias através do mapeamento da concentração de prata por microfluorescência de raios X

• Ano de defesa: 2016
• Autor(a) principal: Gonçalves, Elicardo Alves de Souza
• Orientador(a): Oliveira, Luís Fernando de
• Banca de defesa: Lopes, Ricardo Tadeu , Conti, Cláudio de Carvalho , Assis, Joaquim Teixeira de , Anjos, Marcelino José dos , Machado, Alessandra Silveira
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade do Estado do Rio de Janeiro
• Programa de Pós-Graduação: Programa de Pós-Graduação em Física
• Departamento: Centro de Tecnologia e Ciências::Instituto de Física Armando Dias Tavares
• País: BR
• Palavras-chave em Português: Densidade óptica; Microfluorescência de raios X; Imagem radiográfica
• Palavras-chave em Inglês: Optical density; X-Ray Microfluorescence; Radiographic image
• Área do conhecimento CNPq: CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA::FISICA DA MATERIA CONDENSADA
• Link de acesso: http://www.bdtd.uerj.br/handle/1/12860

The Hurter & Driffield curve, primary tool for the evaluation of radiographic film characteristics is defined as the optical density as a function of exposure. This optical density is traditionally measured by the transmittance of a beam of light through the film, and their it is important to understand the film behavior in sensitometry, scanning by optical scanners and also on visual inspection against a light source, such as a light box. There are many mathematical and computational models to characterize the curve behavior and its properties, but none of them considers the interference caused by the equipment used. In a first approach, in an attempt to fit a theoretical models, it was found that for high values of exposure, there was inconsistency toward the experimental data and the values predicted by theoretical models were higher than the measured values. This inconsistency would suggest a limitation of optical density. When it tried to measure the silver concentration in function of exposure by another method such as X-ray fluorescence, it was noticed that the silver concentration is reasonably according to the models. This led to the conclusion that the limitation perceived in optical density is mainly caused by measurement. The objectives of this thesis were: 1 - To characterize this limitation in measure the optical density; 2 - Suggest X-ray fluorescence as a technique that solves the difficulty caused by this limitation; and 3 - With x-ray microfluorescense, reconstruct images and show what kind of information is hidden and what the new method can reveal. The study shows that the transmittance of light is a limited way of measuring the silver concentration, and gave birth to a mathematical model of this limitation, which established a reasonable fit to the experimental data. The model showed a significant adjustment to the optical density measured when it considered the optical limitation; and also with the silver concentration values when the limitation is disregarded. Three curves were build in function of exposure: one for optical density measured in the traditional way, another to the peak of silver in fluorescence X-ray and a third for model theoretical data. The three data agree with each other to lower exposure values, and above this, only the optical density diverges. Also it was suggested fluorescence X-ray method to circumvent the restriction, showing data that are more consistent with models that do not consider the limitation. The mapping was successful in reconstructing images and show visually that a good portion of the dynamic range is lost with the measurement of light transmission. Details hidden by the lack of contrast due to the optical limitation may be revealed by mapping, so that a fully blackened region of radiography can display an image.