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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
61

Estudo do desempenho de géis de molibdênio formados com diferentes cátions no preparo de geradores de sup(99)Mo-sup(99m)Tc

MORAES, VANESSA 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:50:56Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:02:52Z (GMT). No. of bitstreams: 1 11105.pdf: 5490789 bytes, checksum: e5c917b212eb27dee51d17f19d0021db (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
62

Avaliação in vitro da infiltração de fluidos pela interface implante-pilar intermediário de três sistemas com conexão do tipo cone Morse e da capacidade de vedação de um material / In vitro evaluation of fluid penetration at the implant-abutment interface of three cone Morse systems and sealing ability of a material

Flavia Maria Lopes de Moraes 27 September 2010 (has links)
A infiltração de fluido e bactérias nos espaços internos dos implantes foi observada em pilares intermediários parafusados, tanto em situações in vitro quanto in vivo devido à microfenda existente entre o implante e o pilar intermediário. Esse fato pode estar relacionado com a inflamação dos tecidos periimplantares e também com a produção de mau odor. O objetivo do presente estudo in vitro foi avaliar e comparar a ocorrência de infiltração de fluidos pela interface implante-pilar intermediário em três sistemas de implante com conexão do tipo cone Morse, e a capacidade de vedação de um adesivo anaeróbico, utilizando o radioisótopo Tecnécio-99m como marcador. Na primeira etapa, dez conjuntos implante-pilar intermediário de cada sistema foram imersos em solução contendo esse marcador, após a aplicação do torque recomendado pelo fabricante, e foram mantidos em pressão constante de 2 atm por um minuto. Na segunda etapa, um adesivo anaeróbico foi aplicado no pilar intermediário antes do mesmo ser parafusado ao seu respectivo implante. Após a aplicação da pressão, o infiltrado presente no interior dos implantes foi coletado com pontas de papel. Esse material foi depositado em tubos de ensaio para posterior leitura da radioatividade presente. A infiltração de fluido pela interface implante-pilar intermediário mostrou ser um fenômeno mensurável em todas as amostras dos três sistemas de implante com conexão do tipo cone Morse testados. A quantidade de infiltrado variou entre os sistemas e entre as amostras. A inconstância das amostras foi observada em todos os sistemas, no entanto, foi observado que o valor de infiltrado encontrado no Grupo 1 foi significantemente maior (p<0,05) do que o encontrado no Grupo 2, e não houve diferença estatística significante entre os Grupos 1 e 3, e entre os Grupos 2 e 3. Também foi observado que, com o uso do adesivo anaeróbico, os sistemas apresentaram diminuição da quantidade de infiltrado, sendo que a análise estatística dos valores obtidos com e sem o seu uso, mostraram significância a 1%. Além disso, com o uso do adesivo anaeróbico os três sistemas de implante testados passaram a ter comportamento semelhante, não tendo sido encontrada diferença estatística significante entre eles (p=0,5451). Considerando os limites deste estudo, pode-se concluir que os três sistemas de implante com conexão do tipo cone Morse testados permitiram a passagem de fluido do meio externo para o interior dos implantes, e que o material testado não foi capaz de impedir a penetração de fluido, apesar de ter reduzido significantemente a quantidade de infiltrado em todos os sistemas. / It has been observed that in implants with screw-retained abutments, in in vitro as well as in vivo conditions, bacteria and fluids can penetrate the inner implant space as consequence of an existing microgap at the implant-abutment interface. This fact can be related to peri-implant tissue inflammation and malodor. The aim of the present study was to evaluate and compare the occurrence of fluid penetration throught implant-abutment interface in three cone Morse implant systems and sealing ability of an anaerobic adhesive using a radioisotope as trace. In the first phase, ten implant-abutment sets of each system were immersed in a solution with radioisotope, after manufacture recommended torque application. All assemblies were kept in a constant pressure of 2 atm for one minute. In the second phase, an anaerobic adhesive was applied before the abutments been torque-tightened to the same implant. After the pressure application, material inside implant bodies was colleted using a paper cone that was transferred to tubes for posterior verification of radioactivity. Fluid penetration at the implant-abutment interface was seen to be a recordable phenomenon in each assembly of the three cone Morse systems tested in this study. The quantity of infiltrated varied between systems and assemblies. The variable of the samples was observed in all systems, however, it was noted that the value of infiltrate found in Group 1 was significantly higher than that found in Group 2, and there was no statistical significant difference between the groups 1 and 3, and between groups 2 and 3. It was also noted that, using the adhesive anaerobic, the implant systems showed reduce infiltrate, and statistical analysis presented significance to 1%. Moreover, with the use of anaerobic adhesive, all three implant systems tested presented similar pattern, and no significant statistical difference was found (p=0,5451). Considering the limits of this study, the following conclusions can be drawn: the three cone Morse implant systems tested allowed the passage of fluid from external to the inside of the implants, and that the material tested was not capable of preventing the fluid penetration, despite having reduced significantly the amount of infiltrate in all systems.
63

A preliminary investigation into the estimation of time since death from human skeletal remains by radioisotope and trace element analysis

Howard, Sheridan January 2008 (has links)
One of the first concerns for forensic anthropologists in dealing with skeletal remains in the Australian context is the determination of whether the remains are of anthropological, historical or archaeological interest. If fewer than 75 years have elapsed since death, remains are classified as anthropological and of forensic interest. However, an accurate and reliable method for estimating time since death (TSD) from human skeletal remains has thus far eluded forensic anthropologists. This study investigates the application in an Australian context of a novel approach proposed by Swift (2001) to dating skeletal remains from their contained levels of radioisotopes 210Po, 238U and 226Ra and trace elements. Radionuclide activity concentrations were determined using alpha and gamma spectrometry. Trace element concentrations were measured on three separate occasions using inductively coupled plasma mass spectrometry (ICP-MS). Discriminant analysis of the combination of activity concentration values for 210Po, 238U and 226Ra indicated the possibility of separation of bones derived from individuals who had died in the three eras of interest. Additionally, variations in the concentration levels of specific trace elements and certain inter-element relationships between elements also showed significant correlations with TSD. The study could not be exhaustive as access to human skeletal material was limited and additionally, the archaeological material had a different origin and post-death history to material from the more recent past. However, trend lines for inter-relationships between specific metals and for radionuclides indicated that all material fitted the same generally projected trends and as such, inferences with respect to variations of trace elements and radionuclides could be made with confidence. Bone radionuclide activity and calcium concentrations were all significantly higher in bones from the archaeological era than those from more recent eras, while trace lead concentrations contained in samples from the more recent historical era were significantly higher than those from other eras. Barium, lanthanum, rubidium, strontium, cerium and neodymium concentrations were all significantly correlated with one another and with radionuclide activity concentrations. Differences were found between the patterns of radionuclide activity and trace element concentrations between the skull and femur. The results of this study lend support to suggestions that multivariate analysis of trace element concentrations and radionuclide activity levels could aid in the estimation of time since death from skeletal remains in Australia. Although this study made use of only a limited amount of material, results clearly indicated the need to take into account variations arising from lifetime activities, diagenesis and bone type in applying the techniques to estimations of time since death. It highlights the need for a large-scale study using bone of known ages that systematically examines these influences on the estimation of time since death.
64

Semi-quantificação cintilográfica de defeitos perfusionais em portadores de Doença Falciforme. Comparação com sintomas clínicos

Santos, Vitor Vasquez dos January 2019 (has links)
Orientador: Sonia Marta Moriguchi / Resumo: Introdução: A doença falciforme (DF) é a doença monogênica herdada mais comum no mundo. Acometimentos cardiopulmonares de caráter progressivo associados à vaso oclusão e fenômenos embólicos assim como, as exacerbações de sintomas respiratórios são causas recorrentes de internações nessa população. A cintilografia de perfusão é método de imagem sensível e consagrado para avaliação hipoperfusão pulmonar, notadamente em processos embólicos. A semi-quantiticação da porcentagem de obstrução vascular de perfusão (POVF) apresenta relação segura com a angiografia. Objetivo: 1) Verificar a correlação entre os sintomas clínicos (Classes funcionais) versus Porcentagem de defeitos perfusionais (POVF%) em portadores de DF e 2) Verificar a associação entre POVF% e espirometria, avaliada pela porcentagem da capacidade vital forçada do predito (CVF%). Casuística e Metodologia Trata-se de estudo transversal observacional descritivo de 22 portadores de Doença Falciforme (DF), com coleta retrospectiva de dados clínicos e de espirometria, no período de 2017-2019 e semi-quantificação da cintilografia de perfusão pulmonar (POVF%), CF de I a IV e CVF% Análise estatística descritiva e inferenciais (Coeficiente de correlação – CC), com nível de significância com p<0,05. Resultados: Foram observados cinco subtipos de DF: SS (n=13), BSB0 (n=04), SS+alfatalassemia (n=02), SS+ fetal elevada (n=02) e SC (n=1). A cintilografia de perfusão pulmonar foi sensível identificando defeitos perfusionais em 91% da ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: INTRODUCITON: Sickle cell disease (SCD) is the most common inherited monogenic disease in the world. Cardiopulmonary complications of a progressive character, associated with vessel occlusion and embolic phenomena, such as, exacerbations of respiratory symptoms are recurrent causes of hospitalization in this population. Perfusion scintigraphy is a sensitive and conspicuous imaging method for evaluating pulmonary hypoperfusion, especially in embolic processes. The semi-quantification of the percentage of vascular perfusion obstruction (POVF) presents a safe relationship with angiography. Objective: 1) To verify the correlation between clinical symptoms (functional classes- FC) versus percentage of perfusion defects (POVF%) in patients with CSD and 2) to verify the association between POVF% and spirometry, evaluated by the percentage of forced vital capacity predicted VCF%). MATERIALS AND METHODOLOGY This was a descriptive, observational cross-sectional study of 22 patients with SCD, with retrospective collection of clinical data and spirometry data for the period 2017-2019 and semi-quantification of pulmonary perfusion scintigraphy (POVF%) , FC from I to IV and VCF% Descriptive and inferential statistical analysis (Coefficient of correlation - CC), with level of significance with p <0.05. Results: Five subtypes of SCD: SS (n = 13), BSB0 (n = 04), SS + alphatassemia (n = 02), high fetal SS + (n = 02) and SC (n = 1) were observed. Pulmonary perfusion scintigraphy was sensitive b... (Complete abstract click electronic access below) / Mestre
65

Estudo da permeabilidade, limpeza e contaminação do sistema de canais radiculares, após o preparo químico-cirúrgico e aplicação de laser de alta intensidade / Study of the variation of permeability, cleaning and contamination of the root canal system after preparation and application of highintensity laser

Salgado, Ricardo Julio Cabrales 17 April 2009 (has links)
A importância do aumento da permeabilidade e da limpeza da dentina radicular está ligada à melhora da sanificação e obturação do sistema de canais radiculares. Este estudo teve como objetivo, avaliar as variações da permeabilidade dentinária radicular de dentes humanos, após o preparo químico-cirúrgico e irradiação com laseres de Er: YAG, Nd:YAG, por meio da utilização do radioisótopo 99mTc livre, assim como, analisar, valendo-se da microscopia eletrônica de varredura (MEV) a limpeza, contaminação e aderência bacteriana valendo-se de inoculação de Enterococcus faecalis. Trinta raízes palatinas de primeiros pré-molares superiores humanos hígidos e foram preparadas pela técnica seriada. Posteriormente, foram divididas, aleatoriamente, em 3 grupos experimentais com 10 raízes cada: G1 - controle, G2 - irradiação com laser de Er:YAG e G3 - irradiação com laser de Nd:YAG. As amostras preparadas receberam quantidade suficiente de 99mTc livre no interior do canal radicular para o prenchimento do mesmo e colocadas em tubos de ensaio contendo 1mL de solução salina. Após 1 hora, a contagem do isótopo radioativo (99mTc) foi realizada. Findo esse período, 3 raízes foram processadas para análise da limpeza dentinária radicular por MEV e os canais radiculares das 7 raízes restantes foram contaminados com Enterococcus faecalis por 21 dias. A presença e aderência microbiana foram constatadas e avaliadas por fotomicrografias eletrônicas. O tratamento estatístico dos dados permitiu concluir que a o G3 provocou uma diminuição significativa da permeabilidade dentinária radicular; o G2 e o G1, em relação à permeabilidade dentinária radicular, não apresentaram diferença estatisticamente significante em nível de 5%; o G2 mostrou-se eficiente na limpeza das paredes dentinárias do canal radicular e, o G1 apresentou os menores índices de aderência e contaminação da parede dentinária radicular, nos diferentes terços avaliados, sendo maior no G2, seguido pelo G3. / The permeability increasing and the cleanliness of root dentin walls are important to improve the sanitization and root canal filling. Thus, this study aimed to evaluate the variations of root dentin permeability of human teeth, after endodontic preparation followed by Er:YAG and Nd:YAG laser irradiation, using free Technetium-99m radioisotope (99mTc) as tracer. Additionally, SEM images were analyzed to evaluate the cleanliness of dentin walls and possible bacterial adhesion after Enterococcus faecalis inoculation. Thirty palatal roots of human first pre-molars were prepared by conventional technique. Therefore, the sample were randomly divided into 3 experimental groups with 10 teeth each: G1 - control, G2 - Er:YAG laser irradiation and G3 - Nd:YAG laser irradiation. Samples were filled with free 99mTc and placed in test tubes containing 1ml of saline solution. After 1 hour, the radioactive isotope (99mTc) was counted. After that, 3 roots were processed for analysis of dentin cleaning through SEM images and the 7 remaining roots were infected with Enterococcus faecalis for 21 days. The microbial presence and adhesion were verified and evaluated by SEM. After the statistical treatment (ANOVA), it was concluded that Nd:YAG irradiation significantly decreased dentin permeability. Er:YAG irradiation showed significant differences in cleaning efficacy and the G1 (control) had the lowest rates of adherence and contamination of dentin walls, followed by the G3 and G2.
66

"Avaliação de índices de erodibilidade do solo através da técnica da análise da redistribuição do "fallout" do 137Cs" / Evaluation of soil erodibility index using the 137Cs fallout redistribution analysis

Correchel, Vladia 13 February 2004 (has links)
Entre os parâmetros da USLE (Universal Soil Loss Equation), método mais utilizado na estimativa das perdas de solo por erosão hídrica, a erodibilidade do solo, representada pelo fator K e definida como a taxa de solo perdida por unidade de índice de erosividade, em parcela unitária considerada como padrão (Wischmeier et al., 1971), é o único intrínseco ao solo. Nessas condições padrão o valor encontrado é considerado como o real valor de K. Pelas dificuldades experimentais para obtenção do valor de K para todos os solos, esse fator é geralmente estimado por equações matemáticas empíricas com base em atributos físicos, químicos e mineralógicos do solo. O presente trabalho trata da avaliação de oito métodos de estimativa do fator K da USLE, tomando-se por base estimativas das taxas de erosão avaliadas pelo método do 137Cs. Foram utilizadas oito parcelas padrão de avaliação de perdas de solo e seis transeções demarcadas no campo, em diferentes solos. Nas parcelas padrão, as taxas de erosão medidas diretamente foram comparadas com as estimadas pelo método do 137Cs e os resultados indicaram uma boa concordância. Os valores de K, estimados pelos diferentes modelos, para o solo da parcela, foram comparados diretamente com o valor medido e mostram que os métodos propostos por Wischmeier et al. (1971) e Denardin (1990) desenvolvido para solos do Brasil, são os que mais se aproximam do valor medido. Os mesmos valores de K foram também avaliados por meio da comparação entre as taxas de erosão estimadas pela USLE e pelo método do 137Cs, tendo sido obtidos resultados semelhantes aos da avaliação direta. Essa última forma de avaliação dos métodos de estimativa do fator K foi aplicada também em seis transeções demarcadas em diferentes solos. Devido às grandes limitações associadas aos dois métodos, os resultados mostram uma grande discrepância entre as taxas de erosão estimadas pela USLE e pelo 137Cs o que inviabilizou a comparação proposta dos modelos. / Among the Universal Soil Loss Equation (USLE) parameters, the soil erodibility factor (K), defined as the rate of soil loss per unit of area and per unit of erosivity index for a specific soil as measured on unit plot (Wischmeier & Smith, 1978), is the only soil intrinsic factor. The K values determined on standard unit plots are considered as the real K values. However, K factor can be also estimated by empirical models based on physical, chemical and mineralogical soil attributes. Eight of such empirical methods for K factor estimation were evaluated by comparing the rates of soil loss calculated by USLE and 137Cs fallout redistribution analysis. This procedure was applied both in eight standard erosion plots and six field transects on different soils. In the standard erosion plots the measured soil erosion rates were compared with the rates estimated by the 137Cs method and the results indicate a good relationship. The K values estimated by the different models for the specific soil of the standard plots were compared with the measured K value. The results obtained by the models proposed by Wischmeier et al. (1971) and Denardin (1990) for Brazilian soils were more close to the measured K value. The same K values were also evaluated by comparing the soil erosion rates estimated by USLE and 137Cs methods and the results are in agreement with the direct comparison. This procedure was also applied for the evaluation of K estimation models on the field transects. Due to the limitations associated to both models, the soil erosion rates estimated by USLE and 137Cs methods were very discrepant which did not allow the comparison of K estimation methods when applied for the soils of the transects.
67

O emprego de radioisótopo na avaliação da permeabilidade dentinária intracanal tendo como variáveis as soluções irrigadoras e a irradiação com diferentes lasers / Polietileneglycol 400 marked with Technetium-99m to evaluate the intracanal dentin permeability taking variables as the irrigation solutions and irradiation with different lasers

Yamamoto, Angela Toshie Araki 12 February 2008 (has links)
O objetivo deste experimento foi avaliar as variações da permeabilidade dentinária do sistema endodôntico produzidas pelo protocolo de irrigação intracanal: ácido cítrico a 15%, EDTA-T a 17%, MTAD, Smear Clear e NaCl 0,9% e a influência de diferentes lasers: Diodo, Er:YAG, Nd:YAG, utilizando para isso o radioisótopo Tecnécio-99m (99m Tc) (PARTE a) e o polietilenoglicol 400 (PEG 400) marcado 99m Tc (PARTE b). Foram selecionadas 150 raízes palatinas de molares superiores, divididas em 5 grupos, com 10mL/amostra para realizar a irrigação. Inicialmente analisou-se 10 raízes de cada grupo, introduzindo-se 5?L de 99m Tc no canal radicular, sendo então imersos em NaCl 0,9%, com exceção da superfície da entrada do canal para realizar a contagem da quantidade de radioisótopo dissociado para o meio externo (salina), sendo que se realizou os mesmos procedimentos com a introdução de PEG marcado (5?ci) no canal radicular. Posteriormente, cada um dos grupos experimentais foram subdivididos em outros 3 para irradiação com os diferentes lasers: Diodo (1,5W, modo contínuo, fibra de 300?m de diâmetro); Er:YAG [100mJ (42mJ output),1W, 10Hz, fibra com 0,375?m]; Nd:YAG (100mJ, 1,5Hz, 15W, fibra com 300?m). Repetindo-se os mesmos procedimentos primeiramente com 99m Tc livre e posteriormente o PEG400 marcado com 99m Tc para a realização para a contagem do radioisótopo dissociado na solução salina. Os dados obtidos foram tabulados e a analisados estatisticamente pelo teste Tukey com 95% de confiança. Pôde-se concluir que a irradiação com laser Nd:YAG + irrigação com ácido cítrico, ou com EDTA-T apresentaram os melhores índices de permeabilidade, enquanto que a irrigação com NaCl 0,9% e o MTAD apresentaram os piores índices pe permeabilidade independente da aplicação do laser. O ácido cítrico e o EDTA-T apresentaram os melhores resultados na ausência de irradiação e também no grupo irradiado pelo Er:YAG. E ao irradiar com Diodo a irrigação com EDTA-T apresentou maior permeabilidade. / Assess the variation of root canal dentin permeability produced by intracanal irrigation protocol: 15% citric acid, 17% EDTA-T, MTAD,Smear Clear and 0,9% NaCl and irradiation with different lasers: Diodo, Er:YAG, Nd:YAG using radioisotope technetium-99m (99mTc ) (PART a) and polietileneglycol 400 (PEG) marked with 99mTc (PART b) was the aim of this study. Hundred fifty palatin roots of molar were selected and divided in 5 groups to carry out the irrigation with 10 mL/sample of the solutions. Ten roots of each group were analyzed, introducing 5?L of the 99mTc dissolved in distilled water, with aproximatly 5?L in the root canal and imersed in 0,9% NaCl to carry out the count of amount of 99mTc dissociated to the external enviroment and after introducing 5?L of PEG marked with 99m Tc (5mci). Later, the groups were (PART b) divided to other 3 to irradiate with the folowing parameters: Diodo (1,5W, continuous, 300?m filament); Er:YAG [100mJ (42mJ output),1W, 10Hz, 0,375?m fiber]; Nd:YAG (100mJ, 1,5Hz, 15W, 300?m fiber). The same procedures were repeted to count and the obteined datas were analyzed statistically by the tukey test with 95% reliance. It was concluded that Nd:YAG laser + irrigation with citric acid or EDTA-T have presented the best scores of permeability, while the NaCl and the MTAD presented the worst scores independent of the laser irradiation. The citric acid and the EDTA-T have presented the best results in absence of laser and also, in the group irradiated by Er:YAG laser. Additionaly, if we irradiate with Diode, the EDTA-T group presented higher permeability.
68

La chimie des radio-isotopes; développement de nouvelles connaissances et valorisation sociétale pour la santé et l'environnement

Montavon, G. 21 March 2009 (has links) (PDF)
Je suis arrivé dans le groupe de Radiochimie du laboratoire Subatech en décembre 1998 en tant que chargé de recherche CNRS. Il s'agissait d'un jeune groupe créé par Monsieur Jean-Charles ABBE en 1993. Le laboratoire était alors reconnu pour ses activités de métrologie nucléaire (service SMART) et ses activités de recherche sur la chimie du Technétium et sur l'effet des bactéries sur le migration des radionucléides dans l'environnement. Mon projet de recherche CNRS s'inscrivait en complément des recherches menées. Mon arrivée au laboratoire a coïncidé avec celle du responsable actuel du groupe : Bernd Grambow. Son arrivée a eu pour conséquence un développement et une sensible réorientation des activités de recherche. Aussi, durant ces 8 années, j'ai également développé, en parallèle de mon projet CNRS, d'autres projets en cohérence avec la politique scientifique du groupe. Au jour d'aujourd'hui, je suis responsable de deux projets intitulés " MATIERE COLLOIDALE " et " ARGILES COMPACTEES " qui s'inscrivent dans l'axe " Nucléaire, Energie, Matériaux et environnement " du laboratoire Subatech. Le but est de contribuer aux analyses de sûreté des centres de stockage des déchets nucléaires en surface (centre AUBE) et en couche géologique profonde (laboratoire souterrain de Bures). J'interviens également dans les projets " RADIOELEMENTS ET SANTE " et " BIOMATERIAUX " de l'axe " Nucléaire et Santé ". Il s'agit de projets coordonnés par d'autres laboratoires ligériens dans lesquels je suis l'interlocuteur à SUBATECH. L'ensemble des projets se focalisent autour d'un centre d'intérêt : l'étude des mécanismes d'interaction de solutés d'intérêt avec des molécules organiques et/ou avec des colloïdes minéraux dans le milieu aqueux. Quel que ce soit le projet, la démarche de modélisation des interactions se base d'une part sur une étude expérimentale macroscopique en solution/suspension décrivant le comportement du soluté en fonction des divers paramètres influents et d'autre part, sur une approche spectroscopique (lorsqu'elle est possible) décrivant la nature de l'interaction au niveau moléculaire. Ces recherches relèvent pour l'essentiel de la physico-chimie des interactions en solution et aux interfaces solide/liquide.
69

Small field dose measurements with Gafchromic film

Underwood, Ryan John 09 April 2013 (has links)
Purpose: To examine the dosimetric characteristics of Gafchromic EBT3 film when measuring small fields of radiation, and compare it against other common radiation detectors. Methods and Materials: EBT3 film was placed in a solid water phantom and irradiated with 6MV photons, field sizes from 10x10cm2 down to 6x6mm2. The films were scanned with a Vidar DosimetryPRO Advantage Red scanner, and analyzed with RIT113 software. The films were also scanned at different orientations and times to quantify the discrepancies associated with scanning orientation and post-exposure darkening. The same fields were measured with a PTW TN30013 farmer chamber, an Exradin T1 cylindrical ion chamber, a PTW parallel plate ion chamber, and a Sun Nuclear Edge Detector (diode). Output factors were calculated for each detector and compared for accuracy. The output factors were measured from a Varian Clinac iX, Clinac 21EX, Trilogy, and TrueBeam; as well as a Novalis Tx. The outputs from different machines at different clinics were compared. Results: The EBT3 film and Edge Detector were the only detectors that succeeded in accurately measuring the output from all field sizes; the ion chambers were too large and failed for field sizes below 4x4cm2 due to volume averaging. The dose measured with the film increased by an average of 8.8% after one week post-irradiation. The dose measured was also reduced by an average of 4.4% by scanning the film in landscape orientation, as opposed to portrait orientation. It was shown that the output factors for the smallest field of 6x6mm2--successfully measured with film and diode--varied between 0.54-0.74 for five different machines at three different clinics. Conclusions: The feasibility of using Gafchromic EBT3 film to measure very small fields of radiation is confirmed. Of the other 4 detectors used, only the diode was shown to be capable of accurately measuring small fields of radiation. The need to optimize the film dosimetry process--including the time films are scanned post-irradiation, the consistency of the scanning orientation of the calibration and subsequent films, and the measurement procedure on the computer software--is highlighted.
70

Nickel-63 microirradiators and applications

Steeb, Jennifer L. 30 June 2010 (has links)
In this thesis, manufacturing of microirradiators, electrodeposition of radioactive elements such as Ni-63, and applications of these radioactive sources are discussed. Ni-63 has a half life of 100 years and a low energy beta electron of 67 keV, ideal for low dose low linear energy transfer (LET) research. The main focus of the research is on the novel Ni-63 microirradiator. It contains a small amount of total activity of radiation but a large flux, allowing the user to safely handle the microirradiator without extensive shielding. This thesis is divided into nine chapters. Properties of microirradiators and various competing radioactive sources are compared in the introduction (chapter 1). Detailed description of manufacturing Ni-63 microirradiator using the microelectrode as the starting point is outlined in chapter 2. The microelectrode is a 25 µm in diameter Pt disk sealed in a pulled 1 mm diameter borosilicate capillary tube, as a protruding wire or recessed disk microelectrode. The electrochemically active surface area of each is verified by cyclic voltammetry. Electrodeposition of nickel with a detailed description of formulation of the electrochemical bath in a cold "non-radioactive setting" was optimized by using parameters as defined by pourbaix diagrams, radioactive electroplating of Ni-63, and incorporation of safety regulations into electrodeposition. Calibration and characterization of the Ni-63 microirradiators as protruding wire and recessed disk microirradiators is presented in chapter 3. In chapters 4 through 6, applications of the Ni-63 microirradiators and wire sources are presented. Chapter 4 provides a radiobiological application of the recessed disk microirradiator and a modified flush microirradiator with osteosarcoma cancer cells. Cells were irradiated with 2000 to 1 Bq, and real time observations of DNA double strand breaks were observed. A novel benchtop detection system for the microirradiators is presented in chapter 5. Ni-63 is most commonly measured by liquid scintillation counters, which are expensive and not easily accessible within a benchtop setting. Results show liquid scintillation measurements overestimates the amount of radiation coming from the recessed disk. A novel 10 µCi Ni-63 electrochemically deposited wire acting as an ambient chemical ionization source for pharmaceutical tablets in mass spectrometry is in chapter 6. Typically, larger radioactive sources (15 mCi) of Ni-63 have been used in an ambient ionization scenario. Additionally, this is the first application of using Ni-63 to ionize in atmosphere pharmaceutical tablets, leading to a possible field portable device. In the last chapters, chapters 7 through 8, previous microirradiator experiments and future work are summarized. Chapter 7 illustrates the prototype of the electrochemically deposited microirradiator, the Te-125 microirradiator. In conjunction with Oak Ridge National Laboratory, Te-125m is a low dose x-ray emitting element determined to be the best first prototype of an electrochemically deposited microirradiator. Manufacturing, characterization, and experiments that were not successful leading to the development of the Ni-63 microirradiator are discussed. In chapter 8, future work is entailed in continuing on with this thesis project. The work presented in the thesis is concluded in chapter 9.

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