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Master's Dissertation
DOI
10.11606/D.43.2013.tde-26032014-113306
Document
Author
Full name
Josilene Cerqueira Santos
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2013
Supervisor
Committee
Costa, Paulo Roberto (President)
Freitas, Marcelo Baptista de
Maidana, Nora Lia
Title in Portuguese
Estudo experimental das relações entre Kerma no ar e equivalente de dose ambiente para o cálculo de barreiras primárias em salas radiológicas.
Keywords in Portuguese
Cálculo de Barrieras
Espectros de Raios X
Proteção Radiológica
Abstract in Portuguese
A manutenção dos níveis de dose abaixo dos limites exigidos pelas normas nacionais e internacionais é essencial em todas as aplicações das radiações ionizantes. Os níveis de restrição de dose no Brasil são estabelecidos utilizando a grandeza equivalente de dose ambiente, H* (10) e na prática de levantamentos radiométricos, os níveis de radiação são calculados por meio de medições com câmaras de ionização utilizando a grandeza kerma no ar convertidas para equivalente de dose ambiente por urn coeficiente constante. 0 presente trabalho tern por objetivo o estudo experimental das relações entre kerma no ar e a grandeza operacional equivalente de dose ambiente, pela medição de feixes de raios X transmitidos através de materiais utilizados em salas radiológicas dedicadas à exames de tórax. Uma metodologia experimental, baseada em técnicas de espectroscopia, foi desenvolvida para a medição dos espectros de raios X. Com os resultados, as estimativas da grandeza equivalente de dose ambiente, obtidas através de coeficientes de conversão entre o kerma no ar e esta grandeza, tornam-se mais realistas por levar em consideração as alterações espectrais decorrentes da atenuação dos feixes primários por objetos simuladores antropomórficos e por diferentes materiais atenuadores. Foi encontrada uma diferença máxima de 53,52% entre esses coeficientes e aquele adotado no Brasil por meio da ANVISA (1,14 Sv/Gy), o que indica uma subestimação desse valor. 0 comportamento espectral dos feixes de raios X transmitidos por barreiras primárias e atenuadores presentes em procedimentos radiológicos apresentou influencia sobre resultados relacionados a levantamentos radiométricos e procedimento de cálculos de barreiras.
Title in English
Experimental study of the relationship between air Kerma and ambient dose equivalent for the calculation of primary radiological barriers in rooms.
Keywords in English
Calculation of Barrieras
Radiological Protection
X-ray spectra
Abstract in English
The maintenance of dose levels below the limits required by national and international standards are essential in all applications of ionizing radiation. The dose constrains levels in Brazil are established in terms of the quantity ambient dose equivalent, H*(10), while the radiation levels in radiometric surveys are calculated by means of measurements with ion chambers using the quantity air-kerma converted to ambient dose equivalent by a constant factor. The present work aims the experimental study of the relationship between the air­ kerma and the operational quantity ambient dose equivalent, by measuring X-ray beams transmitted through materials used in dedicated chest radiographic facility. An experimental methodology, based on spectroscopic techniques was developed for the X-ray spectra measurements. With the results, estimates of ambient dose equivalent quantity through conversion factors between this quantity and the air-kerma, become more realistic by taking into account the spectral changes resulting from the attenuation of primary beams by anthropomorphic phantoms and different attenuating materials. The maximum difference founded between these coefficients and the one adopted in Brazil by ANVISA (1.14 Sv I Gy) was 53.52%, which indicates underestimation of the value. The spectral behavior of the X-ray beam transmitted by primary barriers and attenuators present in radiological procedures presented influences on results related to radiometric surveys and procedure calculations barriers.
 
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54771Santos.pdf (6.83 Mbytes)
Publishing Date
2014-09-29
 
WARNING: The material described below relates to works resulting from this thesis or dissertation. The contents of these works are the author's responsibility.
  • SANTOS, J.C., and COSTA, P.R. Evaluation of the Effective Energy of Primary and Transmmitted Workload Weighted X-Ray Spectra [doi:10.1016/j.radphyschem.2013.03.042]. Radiation Physics and Chemistry (1993) [online], 2013, p. on line.
  • COSTA, P. R., and SANTOS, J. C. Qualitative Analysis of X-ray Spectra Transmitted by an Anthropomorphic Phantom and a Shielding Barrier. In International Conference on Radiation protection in Medicine: setting the scene for the next decade, Bonn, Alemanha, 2012. International Conference on Radiation protection in Medicine: setting the scene for the next decade., 2012.
  • SANTOS, J. C., e Costa, P R. Espetros de Raios X Transmitidos por um Objeto Simulador Antropomórfico em Procedimentos de Imagem Torácica. In Congresso Brasileiro de Física Médica, Salvador, 2012. Anais do Congresso Brasileiro de Física Médica., 2012. Resumo.
  • COSTA, P. R., and SANTOS, J. C. Evaluation of the Effective Energy of Primary and Transmmitted Workload Weighted Spectra. In 12th International Symposium on Radiation Physics, Rio de Janeiro, 2012. Anais do 12th International Symposium on Radiation Physics., 2012.
  • SANTOS, J. C., et al. Evaluation of x-ray spectra transmitted by shielding material used in Brazil. In Internationsl Conference of Medical Physics, Brighton, UK, 2013. Medical Physics International. : IOMP, 2013. Abstract.
  • SANTOS, J.C., e COSTA, P.R. Análise da Transmissão de Feixes de Raios X Através de Atenuadores Típicos de uma Sala Radiológica. In Congresso Brasileido de Física Médica, São Pedro, 2013. Anais do Congresso Brasileido de Física Médica., 2013. Resumo.
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