LUCIANA CAMINHA AFONSO
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Resumo IPEN-doc 22223 Estabelecimento de feixes padrões de radiação X de energias médias, nível radioproteção2005 - AFONSO, LUCIANA C.; CALDAS, LINDA V.E.Resumo IPEN-doc 10966 Estabilidade de câmaras de ionização especiais para utilização em programas de controle da qualidade em radioterapia e radiodiagnóstico2004 - AFONSO, LUCIANA C.; CALDAS, LINDA V.E.Resumo IPEN-doc 17548 Dose sensitivity enhancement on polymer gel with suspended gold particles2011 - AFONSO, L.C.; SCHOFER, F.; HOESCHEN, C.; CALDAS, L.V.E.The presence of high-Z materials adjacent to soft tissues, when submitted to irradiation, enhances locally the absorbed dose in these soft tissues. Such effects happen due to the outscattering of photoelectrons from the high-Z materials [1,2,3]. To investigate this effect, polymer gel dosimeters with suspended gold microspheres were used. This study was performed using the polymer gel dosimeter known as MAGIC [4]. The polymer gel was produced and divided into two parts. One part was uniformly mixed with gold microspheres at a concentration of 0.5 % by weight and the other part contained only polymer gel. Each part was poured into test tubes, 4 samples per dose were used, in a range from 0 to 6 Gy. The unirradiated samples were taken as control. The samples were irradiated with X-rays generated at 150 kV, filtered with 4 mm Al and 5 mm Cu, at a constant air kerma rate of 18.9 mGy/min. All samples were read using a Bruker 9.4 T Magnetic Resonance scanner. The transversal relaxation rate R2 (measured in terms of T2=1/R2) from each sample (minus the R2 value from the control) was plotted against the nominal delivered dose to obtain the calibration curves. The samples containing polymer gel with gold microspheres presented approximately 20 % higher change of the R2 value per dose in comparison to the samples containing only polymer gel. This result indicates a dose enhancement factor of approximately 20 %. An analytic estimation predicted a dose enhancement factor of 30 %. The calculations are being refined for a closer description of the experimental parameters.Resumo IPEN-doc 12403 Estudo do comportamento dos feixes de um irradiador gama (sup(137Cs e sup(60)Co a curtas distancias2007 - AFONSO, LUCIANA C.; POTIENS, MARIA da P.A.; CALDAS, LINDA V.E.Artigo IPEN-doc 11035 Estabilidade de camaras de ionizacao especiais para utilizacao em programas de controle da qualidade em radioterapia e radiodiagnostico2004 - AFONSO, L.C.; COSTA, A.M.; CALDAS, L.V.E.Artigo IPEN-doc 10645 Estabelecimento de campos padroes de radiacao X de energias medias no IPEN, nivel radioprotecao2005 - AFONSO, L.C.; CALDAS, L.V.E.Artigo IPEN-doc 12124 Evaluation of an ionization chamber response at small distances during dosimetry of gamma radiation beams2007 - AFONSO, LUCIANA C.; POTIENS, MARIA da P.A.; CALDAS, LINDA V.E.Artigo IPEN-doc 14347 Use of a standard ionization chamber at different distances in diagnostic radiology beams2009 - YOSHIZUMI, M.T.; AFONSO, L.C.; CALDAS, L.V.E.A secondary standard ionization chamber was calibrated, by a primary standard laboratory, at a determined distance. However, in the routine procedures of a calibration laboratory, sometimes the radiation detector cannot be positioned exactly at the calibration distance, for any reason. In this work, the response of a secondary standard ionization chamber was tested to verify the possibility of its use at different distances than at the calibration distance, using the same calibration factor.Artigo IPEN-doc 13447 Study of the influence of scattered radiation at a gamma irradiator2008 - AFONSO, LUCIANA C.; CALDAS, LINDA V.E.The Calibration Laboratory of IPEN offers calibration services for portable radiation monitors using a Buchler gamma irradiator with 137Cs and 60Co radioactive sources. The beam dosimetry measurements are taken periodically between the source-instrument distances of 1m and 4m. The ISO 4037 standard (International Organization for Standardization) states that the air kerma rate due to scattered radiation shall not exceed 5% of that due to direct radiation. To verify if the facility was in accordance to the requirements, the evaluation of the scattered radiation was performed in this work. The air kerma rates were measured on the beam axis at various distances from the source up to 5.5m, and the radiation attenuation curve was obtained. The air kerma rates were proportional within 5% of deviation to the inverse square law from the source centre to the detector centre, as required by the ISO 4037 standard.Artigo IPEN-doc 13383 Comparison between filters with different purities for the HVL determination of X-ray beams2008 - AFONSO, LUCIANA C.; PEREIRA, MARCO A.G.; COSTA, PAULO R.; CALDAS, LINDA V.E.