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Image Quality and Radiation Dose Comparison of a Computed Radiography System and an Amorphous Silicon Flat Panel System in Paediatric Radiography: A Phantom StudyIrvine, Michael Alan, thebovus@yahoo.com January 2009 (has links)
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.
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Visual linearization of image data for the display of digital intraoral radiographs /Li, Gang, January 2004 (has links)
Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 6 uppsatser.
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Avaliação da radiopacidade de diferentes sistemas cerâmicos livres de metalBeghini, Ana Cristina da Rocha Duque 02 May 2011 (has links)
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Previous issue date: 2011-05-02 / No presente estudo avaliou-se a radiopacidade de restaurações cerâmicas livres de
metal de forma objetiva, subjetiva e por meio de MEV/EDS. Foram utilizadas as
cerâmicas: Noritake EX-3 (Noritake), VM13 (Vita), IPS Empress II (Ivoclar Vivadent),
IPS E.max ZirPress (Ivoclar Vivadent) e PM9 (Vita). Para a avaliação objetiva foram
confeccionados cinco corpos de prova nas espessuras de 1, 2, 3 e 4 mm, que foram
radiografados juntamente com uma escala de densidade e uma secção dental,
utilizando-se sistema digital direto. As imagens radiográficas foram submetidas à
leitura de densidade óptica. Para a avaliação subjetiva foram confeccionados
phantoms, simulando a parte posterior das arcadas dentárias, no qual dois dentes
de cada phantom foram submetidos a preparos inlay, restaurados com as cerâmicas
estudadas, e radiografados pela técnica interproximal. Essas radiografias foram
avaliadas por três grupos de examinadores: cirurgiões-dentistas, radiologistas e
protesistas. Para a análise dos elementos químicos que dão características de
radiopacidade aos materiais, foi realizada avaliação pelo MEV/EDS. Os resultados
da avaliação objetiva indicaram diferenças significativas entre as radiopacidades das
cerâmicas estudadas. Para 1 e 2 mm de espessuras todas as cerâmicas
apresentaram radiopacidade superior a da dentina e inferior a do esmalte. A
cerâmica Noritake EX3 apresentou maior radiopacidade em todas as espessuras.
Não se puderam constatar, nas avaliações simulando condições clínicas, as
diferenças de radiopacidades observadas na avaliação objetiva. O grupo dos
cirurgiões-dentistas apresentou a menor acurácia diagnóstica quando comparados
aos grupos de especialistas, sendo que os radiologistas apresentaram a maior
acurácia diagnóstica para cerâmica (0,57). Independente do grupo de avaliadores,
não foi possível a distinção radiográfica entre cerâmicas livre de metal e compósitos.
O resultado da avaliação dos materiais pelo MEV/EDS indicou como possíveis
elementos radiopacificadores: bário para as cerâmicas Noritake EX-3 (2,19%), VM13
(1,04%), PM9 (0,70%) e IPS Empress II (0,70%); e zinco (4,50%) e cério (1,45%)
para a cerâmica IPS E.max ZirPress. / The aim of this study to evaluate the radiopacity of metal-free ceramic restorations in
an objective, subjective and by SEM and EDS. Ceramics were used: Noritake EX-3
(Noritake), VM13 (Vita), IPS Empress II (Ivoclar Vivadent), IPS e.max ZirPress
(Ivoclar Vivadent) and PM9 (Vita). For the objective evaluation were prepared five
specimens with thickness of 1, 2, 3 and 4 mm, which were radiographed with a
aluminum step and a dental section, using direct digital system. The radiographic
images were submitted to the reading of optical density. For subjective evaluation
were fabricated phantoms, simulating the back of the dental arches, in which two
teeth of each phantom received an inlay preparation, were restored with the studied
ceramics, and were x-rayed by the interproximal technique. These radiographs were
evaluated by three groups of examiners, dentists, radiologists, and prosthetists. To
analyze the chemical elements that provide radiopacity characteristics of the
materials, evaluation was performed by SEM and EDS. The results of objective
evaluation indicated significant differences between the radiopacity of the studied
ceramics. For 1 and 2 mm in thickness and the ceramics were all higher radiopacity
dentin and enamel below. Ceramics Noritake EX3 showed higher radiopacity in all
thicknesses. There was evident on the evaluations simulating clinical conditions, the
differences observed in the radiopacity of objective evaluation. The group of dentists
had a lower diagnostic accuracy when compared to groups of specialists, and
radiologists had the highest diagnostic accuracy for ceramics (0.57). Independent
group of evaluators was not possible to distinguish between X-ray and metal-free
ceramic composites. The result of evaluation of materials by SEM and EDS indicated
as possible elements radiopacifiers barium to ceramic Noritake EX-3 (2.19%), VM13
(1.04%), PM9 (0.70%) and IPS Empress II (0.70%) and zinc (4.50%) and cerium
(1.45%) for the ceramic IPS E.max ZirPress.
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