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Vol. 23 No. 1 (2023)
January - June

ARTICULOS DE INVESTIGACION

ON THE CORRECTION OF DOSE PROFILE DISCREPANCIES BY INTRODUCING AIR IN THE DERIVATION OF AN ELECTRON SPECTRUM

https://doi.org/10.19053/1900771X.v23.n1.2023.14751

Published 2023-06-25

  • Jorge Homero Wilches Visbal

Jorge Homero Wilches Visbal
a:1:{s:5:"es_ES";s:25:"Universidad del Magdalena";}

Abstract

Knowledge of the energy spectrum of an electron beam is relevant for accurate dose calculation in radiotherapy. In previous works, it has been possible to reconstruct the electron spectrum of various clinical energies (6, 9, 12 and 15 MeV) within the typical percentage of clinical acceptance (Pa > 95 %) according to the gamma index (GI) (2 %/2mm), for both depth dose percentages (PDD) and dose profiles (DP), except for 6 MeV profiles. Therefore, the purpose of this work was to introduce air between the radiation source and the phantom surface to simulate both the monoenergetic PDDs necessary in the reconstruction of the spectrum of a 6 MeV beam and to obtain the PDD of this spectrum. Validation was performed using the gamma index with the typical threshold for clinical acceptance. The results showed that the PDP of the vacuum spectrum had a better agreement than the PDP of the air spectrum (Pa = 100 %), with respect to the measured PDD (Pa = 97 %). Regarding the PD, the introduction of air improved the agreement in clinical interest but not enough to reach the acceptance percentage. It is concluded that this technique does not seem to be a good alternative to correct the discrepancies in the field edges between the DP of an inversely reconstructed spectrum and the measured DP.

Keywords

inverse reconstruction, electrons, air, gamma index, dose profile

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References

  • J. H. Visbal y A. M. Costa, "Inverse reconstruction of energy spectra of clinical electron beams using the generalized simulated annealing method", Radiat. Phys. Chem., vol. 162, pp. 31-38, Sep. 2019, https://doi. 10.1016/j.radphyschem.2019.04.022.
  • J. H. Wilches Visbal y P. Nicolucci, "Improved reconstruction methodology of clinical electron energy spectra based on Tikhonov regularization and generalized simulated annealing", J. Appl. Res. Technol., vol. 19, n.o 6, pp. 622-632, DSic. 2021, https://doi. 10.22201/ icat.24486736e.2021.19.6.1213.
  • J. H. Wilches Visbal y D. G. Apaza Veliz, "Obtención del espectro de energía de un haz de electrones a partir del método de mínimos cuadrados", Ing. USBMed, vol. 13, n.o 1, pp. 40-45, May 2022, https://doi.10.21500/20275846.5387.
  • A. V. Chvetsov y G. A. Sandison, "Reconstruction of electron spectra using singular component decomposition", Med. Phys., vol. 29, n.o 4, pp. 578- 591, Mar. 2002, https://doi. 10.1118/1.1461840.
  • A. V. Chvetsov y G. A. Sandison, "Angular correction in reconstruction of electron spectra from depth dose
  • distributions", Med. Phys., vol. 30, n.o 8, pp. 2155-2158, Jul. 2003, https://doi. 10.1118/1.1592031.
  • B. A. Faddegon y I. Blevis, "Electron spectra derived from depth dose distributions", Med. Phys.,
  • vol. 27, n.o 3, pp. 514-526, 2000, https://doi.10.1118/1.598919.
  • T. C. Zhu, I. J. Das, y B. E. Bjärngard, "Characteristics of bremsstrahlung in electron beams", Med. Phys.,
  • vol. 28, n.o 7, pp. 1352-1358, Jul. 2001, https://doi.10.1118/1.1382608.
  • J. H. Wilches Visbal y A. M. Da Costa, "Algoritmo de recocido simulado generalizado para Matlab", Ing.
  • y Cienc., vol. 15, n.o 30, pp. 117-140, Nov. 2019, https://doi.10.17230/ingciencia.15.30.6.
  • P. C. Hansen, "Regularization Tools version 4.0 for Matlab 7.3", Number. Algorithms, vol. 46, n.o 2, pp.
  • -194, Nov. 2007, https://doi.10.1007/s11075-007-9136-9.
  • L. Zhengming y D. Jette, "On the possibility of determining an effective energy spectrum of clinical electron beams from percentage depth dose (PDD) data of broad beams", Phys. Med. Biol., vol. 44, n.o 8, pp. 177-182, 1999, https://doi.10.1088/0031-9155/44/8/401.
  • J. H. Wilches Visbal y A. Martins Da Costa, "Determinação da Dose dos Fótons Contaminantes de Feixes de Elétrons Clínicos usando o Método de Recozimento Simulado Generalizado", Rev. Bras. Física Médica, vol. 11, n.o 2, p. 2, Dic. 2017, https://doi.10.29384/rbfm.2017.v11.n2.p2-6.
  • I. J. Chetty et al., "Report of the AAPM Task Group No. 105: Issues associated with clinical implementation of Monte Carlo-based photon and electron external beam treatment planning", Med. Phys., vol. 34, n.o 12, pp. 4818-4853, Nov. 2007, https://doi.10.1118/1.2795842.

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