Computational analysis of 'Dose/Collision Kerma' relationship and lateral boundary in Stereotatic circular fields using EGSnrc.
DOI:
https://doi.org/10.29384/rbfm.2016.v10.n1.p2-8Palavras-chave:
Small Fields, Dosimetry, Monte Carlo, EGSnrcResumo
Objectives: This work aimed to obtain data from small fields of X-rays that evidence of the hypotheses cited as cause of difficulties for the dosimetry of these. For this purpose, the verification of compatibility between the dosimetric boundary of field and the geometric size of field, was performed. Also was made, the verification of kerma dose according to the expected relationship for conventional fields. Materials and Methods: Computer simulations of smaller fields 5x5 cm² were performed using the Monte Carlo method by egs_chamber application, this derived from EGSnrc radiation transport code. As particulate sources were used phase space files of a Clinac 2100 head model coupled to cones Stereotactic Radiosurgery. Results: The simulations suggested the existence of a plateau in discrepancies between the dose FWHM and the nominal diameter of the field close to 8%. These simulations also indicated a decrease of these values for fields with diameters smaller than 12 mm and larger than 36 mm. Simultaneously, the dose kerma differences in depth reached values higher than 14% in the case where the phenomenon is more significant. Conclusion: The data showed that in fact the behavior of small fields clashes with that expected for conventional fields, and that the traditional dosimetric conventions do not apply to such fields requiring a specialized approach to the techniques that employ them. Furthermore, the existence of the aforementioned plateau of discrepancies, along with the decrease thereof in less than 15 mm diameter fields constitute a remarkable finding.
Downloads
Referências
Sean MM, Douglas SW, Bonnie H et al. Hypofractionated Stereotactic Body Radiotherapy in Low-Risk Prostate Adenocarcinoma, Nuclear Instruments and Methods in Physics Research A . 2012, 118, 3681-90.
Yasushi N, Yoshiharu N, Tetsuya A, et al. Clinical Outcomes of 3D Conformal Hypofractionated Single High-Dose Radiotherapy for one or Two Lung Tumors Using A Stereotactic Body Frame, Radiation Oncology Biology and Physics, 2002, 52, 1041-6.
Daniel AL, Jean MM, James FD, et al. Dosimetry tools and techniques for IMRT, 2011, Medical Physics, 38, 1313-38.
Sonja D, Carlo C, Cynthia FC, et al. Report of AAPM TG 135: Quality assurance for robotic radiosurgery, Medical Physics, 2011, 38, 2914-36.
Michael CS, Frank JB, David AL, et al. Stereotactic Radiosurgery: Report of Task Group 42 - Radiation Therapy, Comittee, American Association of Physicists in Medicine, 2011.
Christos A, Evaggelos P. Performance Evaluation of a CyberKnif Robotic Stereotactic RadioSurgery System, Physics in Medicine and Biology, 2008, 53, 4697-718.
Alfonso R, Andreo P, Huq MS, et al. A new formalism for reference dosimetry of small and nonstandard fields, Medical Physics, 2008, 35, 5179-186.
Indra JD, George XD, Anders A. Small Fields: Nonequilibrium Radiation Dosimetry,
Medical Physics, 2008, 35, 206-15.
Philip M, Alan N, Jean-Claude R. Handbook of Radiotherapy Physics: Theory and Practice, Boca Raton: Taylor & Francis Group; 2007.
C-M CM, Alan N. Bragg Gray theory and ion chamber dosimetry for photon beams, 1991, Physics in Medicine and Biology, 36, 413-28.
Attix FH, De La Vergne L, Ritz VH, Cavity ionisation as a function of wall material, 1958, J. Res. NBS, 60, 235.
Attix FH, The partition of kerma to account for bremsstrahlung, Health Phys, 1979, 36, 347–54.
Stanley HB, David JS, Steven JG, et al. Stereotactic Radiosurgery and Stereotactic Body Radiation Therapy, Boca Raton: Taylor & Francis Group; 2015.
Kawrakow I, Mainegra-Hing E, Rogers DWO, et al. The EGSnrc Code System: Monte Carlo Simulation of Electron and Photon Transport, Ottawa: National Research Council Canada, 2016.
Rogers DWO, Walters B, Kawrakow I, BEAMnrc Users Manual, Ottawa: National Research Council Canada, 2016.
Walters B, Kawrakow I, Rogers DWO. DOSXYZnrc Users Manual, Ottawa: National Research Council Canada, 2016.
Reginaldo GLJr, Arno HO, Rômulo VS, et al. Modeling and Commissioning of a Clinac 600 CD by Monte Carlo method using the BEAMnrc and DOSXYZnrc codes, 2015, INAC, São Paulo.
Reginaldo GLJr, Arnaldo PM, Rômulo VS, et al. Desenvolvimento de Geometria Especialista em Dosimetria Numérica de Pequenos Campos por Método de Monte Carlo, Utilizando o Código EGSNRC, 2016, III SENCIR, Belo Horizonte.
Roesch WC, Dose for nonelectronic equilibrieum conditions, 1958, Radiation Research, 9, 399-410.
Downloads
Publicado
Como Citar
Edição
Seção
Licença
A submissão de artigos originais para a Revista Brasileira de Física Médica implica na transferência, pelos autores, dos direitos de publicação impressa e digital. Os direitos autorais para os artigos publicados são do autor, com direitos do periódico sobre a primeira publicação. Os autores somente poderão utilizar os mesmos resultados em outras publicações indicando claramente este periódico como o meio da publicação original. Em virtude de sermos um periódico de acesso aberto, permite-se o uso gratuito dos artigos em aplicações educacionais, científicas, não comerciais, desde que citada a fonte.
A Revista Brasileira de Física Médica está sob a Licença Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0).
