A method for range calculation of proton in liquid water: Validation study using Monte Carlo method and NIST data

Document Type: Conference Proceedings

Authors

1 MSc. Student of medical physics, Department of Medical Physics, Semnan University of Medical Sciences, Semnan, Iran.

2 Professor of medical physics, Department of Medical Physics, Semnan University of Medical Sciences, Semnan, Iran.

3 Professor of physics, Department of Physics, Bojnord University, Bojnord, Iran.

4 Department of Medical Physics, Babol University of Medical Sciences, Babol, Iran

Abstract

Introduction: The main advantage of using ion beams over photons in radiotherapy is due to their inverse depth-dose profiles, allowing higher doses to tumors, while better sparing normal tissues. When calculating dose distributions with ion beams, one crucial point is the uncertainty of the Bragg-peak range. Recently great effort is devoted to enhance the accuracy of the computation for proton treatments without increasing the calculation time. The highest accuracy in these calculations is obtained by Monte Carlo simulation methods. GATE is a Monte Carlo simulation platform based on geant4 which was found to be a convenient simulation environment to perform this study. This study shows how a stochastic method such as Monte Carlo can be utilized to obtain certain quantities of practical importance related to charged particle transport
Materials and Methods: In this study, GATE code was used to compute absorbed dose and fluence of protons in the energy range of 50-200 MeV and with energy step of 50 MeV. A water phantom (40*40*40 cm3) was modeled in a vacuum world volume (5*5*5 m3). Several physics lists have been defined in the GATE code that we used FTFP_BERT. The mono-energetic protons were emitted mono-directionally from a point source at one end of the water phantom. The simulations were carried out for 10^6 proton histories that yielded better than 0.3% statistical errors.
Results: In this study, we validated the Gate code in proton therapy applications. This study examined different physics lists and showed that the results obtained using FTFP_BERT physics are in a good agreement with NIST database. Our Results were compared to the CSDA ranges from NIST database using the GATE simulation code. The FTFP_BERT results showed good agreement within 1% for energies higher than 30 MeV and within 0.1% for energies higher than 70 MeV .We also conclude that the value of 0.1 mm is optimal for the SetCut.
Conclusion: The results were found to be ±0.1% compared to the data from the NIST compilation. It is safe to conclude that this approach can be extended to determine dosimetric quantities for other media, energies and charged particle types.

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