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 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.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 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 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.Artigo IPEN-doc 13365 Characteristics of a tandem system of ionization chambers in X-ray beams mammography level2008 - AFONSO, L.C.; VIVOLO, V.; CALDAS, L.V.E.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.