Inter-comparison of Dose Distributions Calculated by FLUKA, GEANT4, MCNP, and PHITS for Proton Therapy

Zi-Yi Yang,Rong-Jiun Sheu,Pi-En Tsai,Chin-Cheng Chen,Tatsuhiko Sato,Yen-Chiang Liu,Shao-Chun Lee,F Malvagi,C.M’B Diop,J Miss,F Malouch,J.C Trama

doi:10.1051/epjconf/201715304011

Abstract

The dose distributions from proton pencil beam scanning were calculated by FLUKA, GEANT4, MCNP, and PHITS, in order to investigate their applicability in proton radiotherapy. The first studied case was the integrated depth dose curves (IDDCs), respectively from a 100 and a 226-MeV proton pencil beam impinging a water phantom. The calculated IDDCs agree with each other as long as each code employs 75 eV for the ionization potential of water. The second case considered a similar condition of the first case but with proton energies in a Gaussian distribution. The comparison to the measurement indicates the inter-code differences might not only due to different stopping power but also the nuclear physics models. How the physics parameter setting affect the computation time was also discussed. In the third case, the applicability of each code for pencil beam scanning was confirmed by delivering a uniform volumetric dose distribution based on the treatment plan, and the results showed general agreement between each codes, the treatment plan, and the measurement, except that some deviations were found in the penumbra region. This study has demonstrated that the selected codes are all capable of performing dose calculations for therapeutic scanning proton beams with proper physics settings.

Highlights

Proton radiotherapy, compared to the conventional radiation therapy using photons, has the advantages of a more pronounced dose profile, as the so called Bragg peak, and a sharper distal dose falloff (DDF) followed by the Bragg peak
Prior to comparing the proton ranges calculated by different Monte Carlo (MC) codes, it is necessary to check the mean ionization potential (I) of the medium used in each MC code, since the stopping power described by the BetheBloch formula [24-26] is dependent on I-1, and since range is determined by integrating the reciprocal stopping power over energy from the projectile energy down to zero
The ionization potential was set at 75 eV for later calculations in GEANT4 to be consistent with the other codes

Summary

Introduction

Proton radiotherapy, compared to the conventional radiation therapy using photons, has the advantages of a more pronounced dose profile, as the so called Bragg peak, and a sharper distal dose falloff (DDF) followed by the Bragg peak. Monte Carlo (MC) simulations by using the general-purpose radiation transport codes, such as FLUKA [1], GEANT4 [2, 3], MCNPX [4, 5], MCNP6 [6], and PHITS [7], are able to calculate the dose profiles delivered by energetic protons. This study aims to investigate the applicability of these four MC codes in the proton therapy using the pencil beam scanning technique. The simulation results with respect to the accuracy, computing efficiency, and capability of performing complicated source setup of each code were intercompared and discussed in this study. The simulation results were validated by the experimental data

Objectives

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Results

Conclusion