LUCIANA CAMINHA AFONSO
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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.Tese IPEN-doc 17208 Estudo da influência de partículas de ouro na dose absorvida em tecido mole utilizando dosimetria com gel polimérico2011 - AFONSO, LUCIANA C.A presença de material de alto número atômico adjacente ao tecido mole aumenta localmente a dose absorvida pelo tecido quando submetido à radiação. Este efeito ocorre devido aos fotoelétrons ejetados do material de alto número atômico. Dosímetros de gel polimérico com partículas de ouro foram utilizados para investigar este efeito. Foram realizados cálculos analíticos para estimar o aumento de dose e simulações com o método de Monte Carlo. A irradiação de amostras de gel polimérico (GP) puro e com 0,005 gAu/gGP utilizando um feixe de raios X produzido por um potencial de 150 kV filtrado com 4 mmAl e 5 mmCu resultou em uma dose absorvida pelas amostras com ouro aproximadamente 20% maior que a dose absorvida pelas amostras de gel polimérico puro. Os cálculos analíticos e a simulação com o método de Monte Carlo resultaram em um aumento de aproximadamente 30% na dose absorvida.Artigo IPEN-doc 14493 Characteristics of a tandem system of ionization chambers in x-ray beams mammography level2010 - AFONSO, L.C.; VIVOLO, VITOR; CALDAS, L.V.E.Artigo IPEN-doc 18308 Dose sensitivity enhancement on polymer gel with suspended gold particles2012 - AFONSO, LUCIANA C.; SCHOFER, FELIX; HOESCHEN, CHRISTOPH; CALDAS, LINDA V.E.