Neutron radiography is a non-destructive analysis tool that complements X-ray transmission radiography. The use of neutrons provides the ability to image the interior of an object that has a metal core of steel or lead that would shield the interior from X-ray inspection. Neutron tomography is the use of a set of images of a single sample taken at various angles to produce a three dimensional rendition of the sample that greatly increases the effectiveness of neutron radiography as a non-destructive testing tool. A neutron radiography and tomography system has been built at the 1.1 MW TRIGA Mark II nuclear research reactor at The University of Texas at Austin in the Nuclear Engineering Teaching Lab. The Texas Neutron Imaging Facility is located on beam port five of the reactor and is housed in a shielding cave made of concrete to minimize radiation dose to users. The system itself integrates a sample positioning system and neutron sensitive camera through the use of a control code written in National Instruments Labview software. The code was written to increase the efficiency of the imaging process and to provide flexibility in the system. Precise sample positioning and timing of image acquisition provided by the code allows for the collection of data that can be used in computed tomography. The system has produced results in the form of radiographs and 3-D reconstructions of sample objects. / text

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This purpose of this work was to investigate the patient radiation doses and image quality of a Philips/Agfa computed radiographic (CR) system and a Philips indirect-capture digital radiographic (DR) system in a paediatric setting. A CDRAD digital radiographic contrast-detail phantom was used to assess radiographic image quality. Perspex slabs of three different thicknesses (6, 11 and 16 cm) were used to simulate paediatric patients of three arbitrary ages. These phantoms, in conjunction with the CDRAD digital radiographic contrast-detail phantom, were imaged under three different conditions. The CDRAD Analyser software package was used to assess the quality of each image. The first experiment conducted was a comparison of the two systems under standard conditions, with beam filtration of aluminium and copper, as recommended in European Guidelines on Quality Criteria for Diagnostic Radiographic Images in Paediatrics (European Commission 1996b). Image quality was compared for each phantom size at three doses with the same entrance exposure used for both systems. A visual comparison of the resulting contrast detail curves showed the DR system generally outperformed the CR system, especially at the lowest two doses. A chi-square analysis of the targets detected generally confirmed this visual impression. The second experiment performed was to compare the two systems under the conditions used in routine clinical practice at PMH. As a result of additional beam filtration not generally being employed, the image quality of the CR system was similar to the DR system for the two smaller phantom sizes but with a major dose cost - effective doses higher by between 38% and 100%. A chi-square analysis of the targets detected showed the CR system to be significantly better than the DR system at two of three doses for the thinnest phantom and no significant difference at any doses for the intermediate phantom size. For the largest phantom size, additional filtration - although different - was used for the CR and DR systems and so the X-ray beam spectra were more similar. Consequently, the results for this phantom size reflected those from the experiment conducted under standard conditions, ie the effective doses for both systems were similar and the image quality of the DR system superior. The chi-square analysis s howed the DR system to be significantly better than the CR at all three dose levels. A third experiment was undertaken to compare doses between the two systems at 'equal' image quality. The CDRAD Analyser software specific image quality parameter, IQFinv, was held constant for both systems. The entrance exposures required to achieve this image quality were measured and then converted to effective doses using the dose calculation software package PCXMC 1.5. The DR system offered effective dose savings of between 28 and 42% for the three phantom sizes. Overall, this work suggests that a Philips flat-panel system is superior to an Agfa CR system in paediatric radiography. This result generally reflects the findings of other authors who have conducted similar studies in adult patient settings.

Mammography is currently used to screen women in targeted risk classes for breast cancer. Computer assisted diagnosis of mammograms attempts to lower the workload on radiologists by either automating some of their tasks or acting as a second reader. The task of mammogram segmentation based on pixel intensity is addressed in this thesis. The mammographic process leads to images where intensity in the image is related to the composition of tissue in the breast; it is therefore possible to segment a mammogram into several regions using a combination of global thresholds, local thresholds and higher-level information based on the intensity histogram. A hierarchical view is taken of the segmentation process, with a series of steps that feed into each other. Methods are presented for segmentation of: 1. image background regions; 2. skin-air interface; 3. pectoral muscle; and 4. segmentation of the database by classification of mammograms into tissue types and determining a similarity measure between mammograms. All methods are automatic. After a detailed analysis of minimum cross-entropy thresholding, multi-level thresholding is used to segment the main breast tissue from the background. Scanning artefacts and high intensity noise are separated from the breast tissue using binary image operations, rectangular labels are identified from the binary image by their shape, the Radon transform is used to locate the edges of tape artefacts, and a filter is used to locate vertical running roller scratching. Orientation of the image is determined using the shape of the breast and properties of the breast tissue near the breast edge. Unlike most existing orientation algorithms, which only distinguish between left facing or right facing breasts, the algorithm developed determines orientation for images flipped upside down or rotated onto their side and works successfully on all images of the testing database. Orientation is an integral part of the segmentation process, as skin-air interface and pectoral muscle extraction rely on it. A novel way to view the skin-line on the mammogram is as two sets of functions, one set with the x-axis along the rows, and the other with the x-axis along the columns. Using this view, a local thresholding algorithm, and a more sophisticated optimisation based algorithm are presented. Using fitted polynomials along the skin-air interface, the error between polynomial and breast boundary extracted by a threshold is minimised by optimising the threshold and the degree of the polynomial. The final fitted line exhibits the inherent smoothness of the polynomial and provides a more accurate estimate of the skin-line when compared to another established technique. The edge of the pectoral muscle is a boundary between two relatively homogenous regions. A new algorithm is developed to obtain a threshold to separate adjacent regions distinguishable by intensity. Taking several local windows containing different proportions of the two regions, the threshold is found by examining the behaviour of either the median intensity or a modified cross-entropy intensity as the proportion changes. Image orientation is used to anchor the window corner in the pectoral muscle corner of the image and straight-line fitting is used to generate a more accurate result from the final threshold. An algorithm is also presented to evaluate the accuracy of different pectoral edge estimates. Identification of the image background and the pectoral muscle allows the breast tissue to be isolated in the mammogram. The density and pattern of the breast tissue is correlated with 1. Breast cancer risk, and 2. Difficulty of reading for the radiologist. Computerised density assessment methods have in the past been feature-based, a number of features extracted from the tissue or its histogram and used as input into a classifier. Here, histogram distance measures have been used to classify mammograms into density types, and ii also to order the image database according to image similarity. The advantage of histogram distance measures is that they are less reliant on the accuracy of segmentation and the quality of extracted features, as the whole histogram is used to determine distance, rather than quantifying it into a set of features. Existing histogram distance measures have been applied, and a new histogram distance presented, showing higher accuracy than other such measures, and also better performance than an established feature-based technique.

Thesis (M.Sc.)--University of Wollongong, 2005. / Typescript. Includes bibliographical references: leaf 225-238.

Thesis (M.S.D.)--Indiana University School of Dentistry, 2009. / Title from PDF t.p. (viewed Aug. 11, 2009) Advisors: Mychel Vail, Chair of the Research Committee, Susan Zunt, Ted Parks, Kenneth Sponik, Joseph Legan. Curriculum vitae. Includes abstract. Includes bibliographical references (leaves 103-119).

Thesis (M.Tech.: Radiography)-Dept. of Radiography, Durban University of Technology, 2007 xxiv, 142 leaves, Annexures A-L / The aim of the study was to evaluate CT-based treatment planning versus digitised image planning (standard planning technique) for carcinoma of the breast, using the four-field breast technique, in terms of the depth of supraclavicular and axillary nodes, the variability of the breast tissue and the dose inhomogeneity at the matchline.

O exame radiográfico interproximal vem sendo o método mais comumente utilizado como auxiliar no diagnóstico da presença e extensão de lesões de cárie nas superfícies proximais de dentes posteriores e, muitas vezes, funciona como base para a tomada de decisão restauradora. Este estudo tem o objetivo de analisar a possibilidade de previsão de cavitação clínica ou ausência desta nas superfícies proximais em contato de dentes posteriores permanentes e decíduos, de acordo com a extensão da imagem em radiografias interproximais. Para tanto, uma revisão sistemática da literatura foi realizada. Após a formulação da questão de pesquisa estruturada, dois revisores realizaram uma busca nas bases eletrônicas das bibliotecas Medline (PubMed), Embase, LILACS, Scopus e Cochrane. Apenas estudos clínicos foram incluídos. Não houve restrição de idioma ou de data de publicação, sendo incluídos estudos publicados até o mês de abril de 2016. Também foi realizada busca manual nas referências dos artigos selecionados e nas edições da revista Caries Research. Ao final, foram selecionados 11 estudos, os quais apresentaram avaliação da imagem radiográfica e relação com a condição clínica através de diferentes métodos: exame visual associado ou não à separação dentária, seguida ou não de moldagem, ou avaliação após abertura de cavidade em procedimento restaurador com ou sem fotografias. Os resultados da análise qualitativa dos dados mostram que, quando a lesão de cárie apresenta extensão de imagem radiográfica em metade externa de esmalte, a maior probabilidade é de que não haja presença de cavitação clínica; quando a imagem estende-se além da metade ou 2/3 interno de dentina, provavelmente existe cavitação. A discordância mais evidente entre os estudos ocorre quando a imagem radiolúcida atinge a metade interna de esmalte ou metade/terço externo da dentina. Quando na presença deste tipo de imagem radiográfica, o afastamento dentário e inspeção visual estão indicados para a tomada de decisão diagnóstica e consequente decisão de intervenção. Além disso, os fatores que podem influenciar na probabilidade da presença de cavitação clínica devem ser considerados, como padronização da técnica radiográfica, atividade e taxa de progressão de cárie, diferenças populacionais e idade do paciente. / Bitewing radiographic examination has been the most commonly used method to assist the diagnosis of the presence and extension of caries lesions on the proximal surfaces of posterior teeth, and often serves as a basis for restorative decision making. This study aims to analyze the possibility of prediction of clinical cavitation or absence of it in the proximal surfaces of permanent and deciduous posterior teeth, according to the extension of the image in bitewing radiographs. A systematic review of the literature was performed. After formulating the structured research question, two reviewers searched the electronic databases of the Medline (PubMed), Embase, LILACS, Scopus and Cochrane libraries. Handsearch was also carried out on the references of the selected articles and in the editions of the journal Caries Research. Only clinical studies were included. There was no restriction on language or date of publication, included studies published until the month of april of 2016. Eleven studies were selected, which presented an evaluation of the radiographic image and relation with the clinical condition through different methods: visual examination associated or not with dental separation (followed or not by impression) or evaluation during drilling with or without photographs. A qualitative analysis of the data show that when the caries lesion presents radiographic image in the outer half of the enamel, the greatest probability is that there is no clinical cavitation; when the image extends beyond to the inner half or inner 2/3 of dentine, there is a great chance of cavitation. The most evident discordance among studies occurs when the radiolucent image reaches the cut-off point of the inner half of the enamel or external half / third of the dentin. When in the presence of this type of radiographic image, the dental separation and visual inspection are indicated for the diagnostic decision making and consequent intervention decision. In addition, factors that may influence the probability of the presence of clinical cavitation should also be considered, such as standardization of the radiographic technique, activity and rate of caries progression, population differences and age of the patient.

Made available in DSpace on 2014-06-11T19:33:28Z (GMT). No. of bitstreams: 0 Previous issue date: 2005-08-29Bitstream added on 2014-06-13T20:05:24Z : No. of bitstreams: 1 sakakura_ce_dr_arafo.pdf: 1061463 bytes, checksum: 369280e6910c622911b9659ba1e551ac (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Agentes imunossupressores provocam alterações severas no metabolismo ósseo mineral podendo resultar em osteopenia. Tais alterações podem ser prejudiciais no processo e manutenção da osseointegração. Este estudo teve o objetivo de avaliar a influência da administração de ciclosporina-A (CSA) na osseointegração de implantes de titânio, através da avaliação: durante a cicatrização óssea ao redor de implantes dentais (Estudo I); da densidade óssea ao redor implantes dentais (Estudo II); da retenção do implante após a cicatrização óssea de implantes dentais (Estudo III) e radiográfica da qualidade óssea ao redor de implantes dentais já osseointegrados (Estudo IV). Os resultados permitiram concluir que a administração de CSA durante a cicatrização óssea resulta em diminuição da osseointegração e da densidade óssea ao redor do implante dental. Ainda, a administração de CSA após o período de cicatrização óssea ao redor do implante reduz a sua retenção mecânica ao tecido ósseo e promove a diminuição da qualidade e da densidade óssea radiográfica ao redor do implante dental. / Immunosupressive agents may induce severe changes on bone mineral metabolism resulting in osteopenia. These alterations may impair the osseointegration processes. The purposes of this study were evaluate the cyclosporin-A (CSA) influence: on bone healing around dental implants (Study I); on bone density around dental implants (Study II); on mechanical retention of dental implants integrated to the bone (Study III) and on radiographic bone density and quality around dental implants integrated to the bone (Study IV). The CSA administration may impair the osseointegration and bone density during the bone healing. Besides, the administration of CSA after bone healing may impair the dental implant mechanical retention and decrease the radiographic bone density and bone quality around dental implants integrated to the bone.

Made available in DSpace on 2014-10-09T12:25:41Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:03:40Z (GMT). No. of bitstreams: 1 06914.pdf: 2955248 bytes, checksum: 106449a86e70d89b0638f2132a9326c4 (MD5) / Tese [Doutoramento] / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP