Filipuzzi, Maximiliano J. (2013) Determinación experimental de penumbra de pequeños haces de radiación y corrección por función de repuesta mediante deconvolución. / Experimental determination of small beams of radiation and correction by response function through deconvolution. Maestría en Física Médica, Universidad Nacional de Cuyo, Instituto Balseiro.
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Resumen en español
La dosimetría de pequeños campos de radiación es un reto debido a la falta de equilibrio de partículas cargadas (CPE), al bloqueo parcial de la fuente y al tamaño de los detectores utilizados (1). Por esta razón se requiere una gran precisión en la medición de los perfiles de dosis del campo radiante (2). La exactitud con la cual la dosis absorbida puede ser conocida en los bordes de campo depende del conocimiento de la función de respuesta espacial de los detectores (3) (4). La determinación de la misma permite conocer el comportamiento del detector, pudiendo corregir las mediciones, eliminando las perturbaciones introducidas y estimando el perfil real del campo radiante. El objetivo de este trabajo fue comparar la distribución de dosis de dos sistemas de colimación de radiocirugía (micro-multiláminas y conos) y calcular la función de respuesta de una serie de detectores de radiación de distinto diámetro, para distintos tamaños de campo. Los resultados mostraron una mejor conformación del haz con el sistema de conos, disminuyendo la penumbra (de 1,84mm a 1,39mm) y la dosis de fondo fuera del campo. Con respecto a las funciones de respuesta, se evidenció una independencia con el tamaño de campo y se concluyó que una gaussiana de desviación estándar igual al radio del detector corrige los perfiles medidos con una diferencia al perfil real menor a 0,1mm, en la zona de penumbra.
Resumen en inglés
Dosimetry of small fields is challenging due to the lack of charged particle equilibrium (CPE), the partial obstruction of the source and the size of detector used (1). The use of small fields requires great precision in the measurement of the dose in the penumbra area of the radiant field (2). The accuracy with which the absorbed dose can be known at the field’s edges depends on the knowledge of the spatial response of the detector (3) (4). The determination of these response functions allows knowing the spatial behavior of the detector, and can be used to correct the measurements using deconvolution techniques, eliminating the perturbations introduced, and estimating the real profile of the radiation field. Therefore, the aim of this study was to compare the dose distribution of two collimation systems of radiosurgery (micro-multileaf and cones) and calculate the response function of a series of radiation detectors for different field sizes. The results showed a better conformation with the cones collimation system, reducing the penumbra (from 1,84mm to 1,39mm) and the background dose outside the field. The detector response function does not depends on the field size, and the use of a single Gaussian function with a standard deviation equal to the detector’s radio corrects the profiles with a difference less than 0,1mm to the real profile.
| Tipo de objeto: | Tesis (Maestría en Física Médica) |
|---|---|
| Palabras Clave: | Dosimetry; Dosimetría; Doses; Dosis; Collimators; Colimadores; [Penumbra; Deconvolution; Deconvolución; Small radiation beams; Pequeños haces de radiación] |
| Referencias: | 1. Das, I, Ding, G, Ahnesjö, A. Small fields: Nonequilibrium radiation dosimetry. Medical Physics, 35, 206-217, 2007. 2. Alfonso, R, Andreo, P. A new formalism for reference dosimetry of small and nonstandard fields. Medical Physics, 35(11), 5179-5186, 2008. 3. Higgins, P, Sibata, C, Siskind, L, Sohn, J. Deconvolution of detector size effect for small field measurement. Medical Physics, 22, 1663-1666, 1995. 4. Francescon, P, Cora, S, Cavedon, C. Use of a new type of radiochromic film, a new parallel-plate micrho-chamber, MOSFETs, and TLD800 microcubes in the dosimetry of small beams. Medical Physics, 25(4), 503-511 ,1998. 5. García-Garduño, O, Lárraga-Gutiérrez, J, Rodríguez-Villafuerte, M. Small photon beam measurements using radiochromic film and Monte Carlo simulations in a water phantom. Radiotherapy and Oncology, 96, 250-253, 2010. 6. Attix, Frank Herbert. Introduction to Radiological Physics and Radiation Dosimetry. Wisconsin : Wiley-VCH, 2004. 978-0-471-01146-0. 7. Bassinet, C, Huet, C, Derreumaux, S. Small fields output factors measurements and correction factors determination for several detectors for a CyberKnife and linear accelerators equipped with microMLC and circular cones. Medical Physics, 40(7), 2013. 8. Johns, Harold Elford y Cunningham, John Robert. The Physics of Radiology (Fourth Edition). s.l. : Charles C Thomas, 1983. 0-398-04669-7. 9. Chin, Lawrence S. y Regine, William F. Principles and Practice of Stereotactic Radiosurgery. s.l. : Springer, 2008. 978-0-387-71069-3. 10. Keller, B, Beachey, D, Pignol, J. Experimental measurement of radiological penumbra associated with intermediate energy x-rays (1 MV) and small radiosurgery field sizes. Medical Physics, 34(7), 2007. 11. O'Malley, L, Pignol, JP, Beachey, DJ. Improvement of radiological penumbra using intermediate energy photons (IEP) for stereotactic radiosurgery. Phys. Med. Biol., 51(1), 2537-2548, 2006. 12. García-Vicente, F, Delgado, J, Rodríguez, C. Exact analytical solution of the convolution integral equation for a general profile fitting function and Gaussian detector kernel. Phys. Med. Biol.45, 645, 2000. 13. Influence of Ionization Chamber Size for Intesity Modulation Treatment Planning Modeling. Venencia, C.D., Besa, P., Somarriba, F. Washington : 47th AAPM Annual Meeting, 2005. 14. Schell, M., Bova, F. Report of Task Group 42 - AAPM REPORT NO. 54. s.l. : AAPM, 1995. 15. Wilcox, E, Daskalov, G. Evaluation of GAFCHROMIC EBT film for CyberKnife dosimetry. Medical Physics, 31(6), 2007. 16. Cheung, T, Butson, M. Measurement of high energy x-ray beam penumbra with Gafchromic EBT radiochromic film. Medical Physics, 33(8), 2006. 17. Fiandra, C, Fusella, M. Comparison of Gafchromic EBT2 and EBT3 for patient-specific quality assurance: Cranial stereotactic radiosurgery using volumetric modulated arc therapy with multiple noncoplanar arcs. Medical Physics, 40(8), 2013. 18. Lárraga-Gutiérrez, J, García-Hernández, D. Evaluation of the Gafchromic EBT2 film for the dosimetry of radiosurgical beams. Medical Physics, 39(10), 2012. 19. Reinhardt, S, Hillbrand, M. Comparison of Gafchromic EBT2 and EBT3 films for clinical photon and proton beams. Medical Physics, 39(8), 5257-5262, 2012. 20. Menegotti, L, Delana, A, Martignano, A. Radiochromic film dosimetry with flatbed scanners: A fast and accurate method for dose calibration and uniformity correction with single film exposure. Medical Physics, 35(3078), 2008. 21. García-Vicente, F, Delgado, JM, Peraza, C. Experimental determination of the convolution kernel for the study of the spatial response of a detector. Medical Physics, 25(2), 1998. 22. Bassinet, C, Robbes, I, Barbier, L. Characterization of 7LiF:Mg,Ti TLD micro-cubes. Radiation Measurements, 45, 646-648, 2010. 23. Da Rosa, L, Regulla, D. Reproducibility study of TLD-100 micro-cubes at radiotherapy level. Appl. Radiat. Isot., 50(573), 1999. 24. Yu, C, Jozsef, G. Measurements of the relative output factors for CyberKnife collimators. Neurosurgery, 54(157), 2004. 25. Kron, T, Elliott, A, Metcalfe, T. The penumbra of a 6-MV x-ray as measured by thermoluminescent dosimetry and evaluated using an inverse square root function. Medical Physics, 20(5), 1429-1438. 1993. 26. Dosimetry, PTW. Detectors: including Codes of Practice. Ionizing Radiation. 2013. 27. Diamond Dosimetry. Das, I.J. AAPM Summer School - Clinical Dosimetry Measurements in Radiotherapy, 2009. 28. Desrosiers, MF, Peters, M, Puhl, JM. A study of the alanine dosimeter irradiation temperature coefficient from 25 to 80 °C. Radiation Physics and Chemistry, 78, 465-467, 2009. 29. Pappas, E, Maris, T, Papadakis, A. Experimental determination of the effect of detector size on profile measurements in narrow photon beams. Medical Physics, 33(10), 2006. 30. Beddar, A. Plastic scintillation dosimetry and its application to radiotherapy. Radiation Measurements, 41, 2006. 31. Beddar, AS, Mackie, TR. Water-equivalent plastic scintillation detectors for high-energy beam dosimetry: II. Proporties and measurements. Phys. Med. Biol., 37, 1901-1913, 1992. 32. Beddar, A, Mason, D. Absorbed dose perturbation caused by diodes for small field photon dosimetry. Medical Physics, 21(7), 1994. 33. Dosimetry, PTW. Small Field Dosimetry: Application Guide. Radiation Therapy. 2013. 34. Metcalfe, P. Dosimetry of 6 MV x-ray beam penumbra. Medical Physics, 20, 1934-1939, 1993. 35. Engl, H. W., Hanke, M. y Neubauer, A. Regularization of Inverse Problems. s.l. : Kluwer Academic Publishers, 1996. 36. Richardson, W. Bayesian-Based Iterative Method of Image Restoration. Journal of the Optical Society of America, 62, 1970. 37. Fish, D, Brinicombe, A, Pike, E. Blind deconvolution by means of the Richardson-Lucy algorithm. J. Opt. Soc. Am, 12(1), 1995. 38. Khan, M, Morigi, S. Iterative methods of Richardson-Lucy-type for image deblurring. Numerical Mathematics: Theory, Methods and Applications, 12, 2003. 39. Yan, G, Fox, C. The extraction of true profiles for TPS commissioning and its impact on IMRT patient-specific QA. Med. Phys., 35(8), 2008. 40. Fox, C, Simon, T. Assessment of the setup depende of detector response functions for megavoltaje linear accelerators. Med Phys, 37, 2010. |
| Materias: | Medicina > Radioterapia Medicina > Dosimetría |
| Divisiones: | Instituto privado de radioterapia (Córdoba) |
| Código ID: | 437 |
| Depositado Por: | Marisa G. Velazco Aldao |
| Depositado En: | 11 Abr 2014 10:27 |
| Última Modificación: | 11 Abr 2014 10:27 |
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