Introducing a Method to Derive a Multiple Virtual Point Source Model of Linac for Photon Beam Dose Calculation Using Monte Carlo Method

Jabbari, I; Shahriari, M; Aghamiri, S.M.R; Monadi, SH

Introducing a Method to Derive a Multiple Virtual Point Source Model of Linac for Photon Beam Dose Calculation Using Monte Carlo Method

Document Type : Research Paper

Authors

I Jabbari

M Shahriari

S.M.R Aghamiri

SH Monadi

Abstract

In this study a new simple but a very effective method is introduced for the beam modeling of the invariant part of a medical linear accelerator. In this method, instead of segmentation of scoring plane and analysis of phase space file, the mirror image of a virtual point source, energy and angular distributions and dependencies between them are derived, directly. Then, the method was used for the beam modeling of a 6MeV photon beam of the Siemens ONCOR Impression accelerator, where the TALLYX capability of MCNP4C was used. Consequently, a multiple point source model with angular dependent photon energy spectra was obtained. Then, the percentage depth dose curves and the lateral dose distributions in water phantom were calculated using the present model for three field sizes including 4cm×4cm, 10cm×10cm and 40cm×40cm, and the results were compared to those of full Monte Carlo simulations. The results showed excellent agreement between them for all the field sizes. The benefits ofthe present method were verified as comparedwiththephasespacefileanalysismethod,including the easeofapplicationand the errors removal caused by the spatial segmentation of the phase space data.

Highlights

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D.W.O. Rogers, B.A. Faddegon, G.X. Ding, C.M. Ma, J.S. Wei, T.R. Mackie, “BEAM: a Monte Carlo code to simulate radiotherapy treatment units,” Med. Phys. 22, 503–24 (1995).

C.M. Ma, B.A. Faddegon, D.W.P. Rogers, T.R. Mackie, “Accurate characterization of Monte Carlo calculated electron beams for radio-therapy,” Med. Phys. 24, 401–16 (1997).

J. Deng, S.B. Jiang, A. Kapur, J. Li, T. Pawlicki, C.M. Ma, “Photon beam characterization and modelling for Monte Carlo treatment planning,” Phys. Med. Biol. 45, 411–27 (2000).

M.K. Fix, M. Stampanoni, P. Manser, E.J. Born, R. Mini, P. Ru¨egsegger, “A multiple source model for 6MV photon beam dose calculations using Monte Carlo,” Phys. Med. Biol. 46, 1407–1457 (2001).

D. Scora and B. Faddegon, “A Monte Carlo based phase-space evolution for electron dose calculation,” Med. Phys. 24, 177–87 (1997).

W. van der Zee and J. Welleweerd, “Calculating photon beam characteristics with Monte Carlo techniques,” Med. Phys. 26, 1883–92 (1999).

M.K. Fix, H. Keller, E.J. Born E J, P. R¨uegsegger, “Simple beam models for Monte Carlo photon dose calculations in radiotherapy,” Med. Phys. 27, 2739–47 (2000).

A. Chaves, M.C. Lopes, C.C. Alves, C. Oliveira, L. Peralta, P. Rodrigues, A. Trindade, “A Monte Carlo multiple source model applied to radiosurgery narrow photon beams,” Med. Phys. 31, 2192-2204 (2004).

I. Chetty, J.J. DeMarco, T.D. Solberg, “A virtual source model for Monte Carlo modeling of arbitrary intensity distributions,” Med. Phys. 27(1), 165-172 (2000).

A.E. Schach von Wittenau, L.J. Cox, P.M. Bergstrom, W.P. Chandler, C.L. Hartmann Siantar, R. Mohan, “Correlated histogram representation of Monte Carlo derived medical accelerator photon-output phase space,” Med. Phys. 26, 1196-1211 (1999).

Keywords

Monte Carlo Simulation

MCNP

Photon Beam Modeling

Medical Linear Accelerator

1. T. Yamamoto, T. Mizowaki, Y. Miyabe, H. Takegawa, Y. Narita, S. Yano, Y. Nagata, T. Teshima, M. Hiraoka, “An integrated Monte Carlo dosimetric verification system for radiotherapy treatment planning,” Phys. Med. Biol. 52, 1991-2008 (2007).
2. P. Schiapparelli, D. Zefiro, G. Taccini, “Dosimetric verification of a commercial Monte Carlo treatment planning system (VMC++) for a 9MeV electron beam,” Med. Phys. 36(5), 1759-1767 (2009).
1. D.W.O. Rogers, B.A. Faddegon, G.X. Ding, C.M. Ma, J.S. Wei, T.R. Mackie, “BEAM: a Monte Carlo code to simulate radiotherapy treatment units,” Med. Phys. 22, 503–24 (1995).
1. C.M. Ma, B.A. Faddegon, D.W.P. Rogers, T.R. Mackie, “Accurate characterization of Monte Carlo calculated electron beams for radio-therapy,” Med. Phys. 24, 401–16 (1997).
1. J. Deng, S.B. Jiang, A. Kapur, J. Li, T. Pawlicki, C.M. Ma, “Photon beam characterization and modelling for Monte Carlo treatment planning,” Phys. Med. Biol. 45, 411–27 (2000).
1. M.K. Fix, M. Stampanoni, P. Manser, E.J. Born, R. Mini, P. Ru¨egsegger, “A multiple source model for 6MV photon beam dose calculations using Monte Carlo,” Phys. Med. Biol. 46, 1407–1457 (2001).
1. D. Scora and B. Faddegon, “A Monte Carlo based phase-space evolution for electron dose calculation,” Med. Phys. 24, 177–87 (1997).
1. W. van der Zee and J. Welleweerd, “Calculating photon beam characteristics with Monte Carlo techniques,” Med. Phys. 26, 1883–92 (1999).
1. M.K. Fix, H. Keller, E.J. Born E J, P. R¨uegsegger, “Simple beam models for Monte Carlo photon dose calculations in radiotherapy,” Med. Phys. 27, 2739–47 (2000).
1. A. Chaves, M.C. Lopes, C.C. Alves, C. Oliveira, L. Peralta, P. Rodrigues, A. Trindade, “A Monte Carlo multiple source model applied to radiosurgery narrow photon beams,” Med. Phys. 31, 2192-2204 (2004).
1. I. Chetty, J.J. DeMarco, T.D. Solberg, “A virtual source model for Monte Carlo modeling of arbitrary intensity distributions,” Med. Phys. 27(1), 165-172 (2000).
1. A.E. Schach von Wittenau, L.J. Cox, P.M. Bergstrom, W.P. Chandler, C.L. Hartmann Siantar, R. Mohan, “Correlated histogram representation of Monte Carlo derived medical accelerator photon-output phase space,” Med. Phys. 26, 1196-1211 (1999).