ESTUDO DA INFLUÊNCIA DE PARTÍCULAS DE OURO NA DOSE ...

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IC3DDose 2010 – 6th International Conference on 3D Radiation DosimetryX-raysMonitor ChamberFiltersDiaphragmsAluminiumsupportFoam0 34 4370Distance (cm)37 48Figure 2: Irradiation set-up (not to scale).3.3. NMR ScanningAfter approximately 17 hours the samples were scanned using a Bruker BioSpin system (BioSpec94/20 USR, 9.4 T). A Multi Slice Multi Echo sequence (MSME) was used with FOV = 6 x 6 cm 2 ,echo times of 20, 40, …, 320 ms and a repetition time of 2500 ms. One slice with 1mm thickness wasmeasured in the surface of each sample. The T2 values were obtained by fitting all signal echoes to amonoexponential function. Then, the transversal relaxation rates (R2 = 1/T2) were related to the doses.Two R2 in different regions of interest (ROI) per sample were measured; one under the area coveredby the gold foil and the other out of the area covered with gold. The gold foils were removed beforethe scanning.4. Results and DiscussionThe relation between R2 and the dose is represented in the Figure 3. It is observed that the relaxationrates measured under the gold foils are greater than those measured in the area free of gold. One canobserve that the slope from the linear regression of the measurements in the area with gold is greaterthan the slope obtained from the measurements in the area without gold. This indicates that thepresence of gold foils on the surface of the samples caused a dose enhancement in the vicinity of thesegold foils by 16 %. This result can serve just as an estimate because of two important factors: thethickness of the gold foils was not known exactly; and the gold foils were very flexible and easily torn,so the difficulty of dealing with such foils caused that some small areas were not well covered.459
R2 (s -1 )IC3DDose 2010 – 6th International Conference on 3D Radiation Dosimetry7.06.5Slope Intercept R 2No Au 0.304 4.551 0.98With Au 0.354 4.595 0.97No AuWith Au6.05.55.04.50 1 2 3 4 5 6Dose (Gy)Figure 3: Relation between R2 and the dose. The red squares represent the area covered with goldfoils and the black lozenges represent the area not covered with gold foils. The error bars represent thestandard deviation of the R2 in the ROI.5. ConclusionThe result of this study indicates the effect of dose enhancement in the area adjacent to the goldfoils. Nevertheless, taking into account that difficulties mentioned above may play an important role,the experiment will be repeated using more resistant gold surfaces (i.e., thicker foils or plates) in orderto assure this result and achieve a better quantification. The scanning will be performed with thinnerslices, with a sequence of slices into the depth of the gels.References[1] Regulla D, Friedland W, Hieber L et al (2000) Spatially Limited Effects of Dose and LETEnhancement Near Tissue/Gold Interfaces at Diagnostic X Ray Qualities. RadiationProtection Dosimetry, 90, Nos 1–2, pp. 159–163[2] Regulla D, Panzer W, Schmid E et al (2001) Detection of Elevated RBE in HumanLymphocytes Exposed to Secondary Electrons Released from X-Irradiated Metal Surfaces.Ratiation Research, 155, pp. 744–747[3] Herold DM, Das IJ, Stobbe CC et al (2000) Gold Microspheres: a Selective Technique forProducing Biologically Effective Dose Enhancement. International Journal of RadiationBiology, 76, No 10, pp. 1357-1364[4] Alexander P, Charlesby A, Ross M (1954) The Degradation of Solid Polymethyl-methacrylateby Ionizing Radiations. Proceedings of the Royal Society, pp. 392-404[5] Hoecker FE, Watkins IW (1958) Radiation Polymerization Dosimetry. International Journal ofApplied Radiation and Isotopes, 3, pp. 31-36[6] Maryanski MJ, Gore JC, Schulz RJ (1992) 3-D Radiation Dosimetry by MRI: Solvent ProtonRelaxation Enhancement by Radiation-Controlled Polymerisation and Cross-Linking inGels. Proc. Intl. Soc. Mag. Reson. Med.460
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AUTARQUIA ASSOCIADA À UNIVERSIDADE
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AGRADECIMENTOSÀ Dra. Linda V. E. C
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STUDY OF THE INFLUENCE OF GOLD PART
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5.1.3 Dependência do Dosímetro em
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A resposta dos tecidos às radiaç
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1978), indicando que pode haver um
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delta (δ). Feixes contínuos de el
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da energia do fóton. Quando intera
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Figura 3.1 - Esquema de interação
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material atravessado. A Figura 3.2
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em que E b é a energia de ligaçã
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esultados experimentais, complement
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Já o processo de transição não
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K tr(Eq. 3.24)Outra grandeza impor
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comum. Este tipo de gel ficou conhe
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Estes radicais peróxido reagem rap
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submetidos ao mesmo campo magnétic
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t T1M zM01 e(Eq. 3.45) em que T
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3.4.4 Avaliação dos Dosímetros d
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3.5 Método de Monte CarloO método
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A probabilidade de obter um valor d
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método de Monte Carlo. Porém, par
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Tabela 4.1 - Especificações dos f
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- Sistema de Ressonância Magnétic
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5 METODOLOGIA E RESULTADOSNeste cap
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Os parâmetros TE (tempo de eco, in
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Figura 5.3 - Ajuste monoexponencial
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Tubo de raios XFiltrosCâmara monit
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IA = 1, 4 e 5 dias.Figura 5.8 - PI
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Figura 5.9 - Relação entre R 2 -R
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As amostras foram avaliadas 1 dia a
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As amostras foram avaliadas 1 dia a
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polimérico deveriam seguir uma dis
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Coeficiente angularFigura 5.16 - Re
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Coeficiente angularOs dados de cada
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Page 73 and 74: 5.3 Experimentos Preliminares com F
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Page 77 and 78: sem ouro.Figura 5.24 - Relações e
Page 79 and 80: 5.4 Feixes de Raios X que aumentam
Page 81 and 82: Figura 5.28 - Espectro do feixe N-8
Page 83 and 84: Figura 5.32 - Espectro do feixe N-2
Page 85 and 86: Figura 5.34 - Espectros dos feixes
Page 87 and 88: Tabela 5.4 - Composição detalhada
Page 89 and 90: Figura 5.36 - Coeficiente de absor
Page 91 and 92: para o tecido mole padrão da ICRP
Page 93 and 94: 0,005 gAu/gGP apresenta um aumento
Page 95 and 96: Fator de aumento de doseOs valores
Page 97 and 98: Figura 5.45 - Distribuição da tax
Page 99 and 100: Figura 5.47 - Relação entre a dos
Page 101 and 102: Figura 5.49 - Aumento da dose absor
Page 103 and 104: Figura 5.51 - Espectros dos feixes
Page 105 and 106: R 2 - R 2 (0) (s -1 )Esta diferenç
Page 107 and 108: R 2 - R 2 (0) (s -1 )com microesfer
Page 109 and 110: Fator de aumento de doseprevisto, p
Page 111 and 112: Os coeficientes de absorção máss
Page 113 and 114: 7 REFERÊNCIASAFONSO, L.C.; SCHÖFE
Page 115 and 116: MARYANSKI, M.J.; GORE, J.C.; KENNAN
Page 117 and 118: Anexo: Trabalhos publicados em anai
Page 119 and 120: Absorbed Dose Enhancement Caused by
Page 121: IC3DDose 2010 - 6th International C
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ESTUDO DA INFLUÊNCIA DE PARTÍCULAS DE OURO NA DOSE ...

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