GEANT4 Simulation of Proton Beam Properties from a Cyclotron Accelerator at King Chulalongkorn Memorial Hospital
The main objective of proton beam therapy is to precisely irradiate diseased tissue while minimizing damage to healthy cells. For effective treatment, the linear energy transfer (LET) is a key parameter in ensuring the destruction of diseased cells, and both the dose and LET are typically represente...
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| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-07-01
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| Series: | Applied Sciences |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2076-3417/15/14/7670 |
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| Summary: | The main objective of proton beam therapy is to precisely irradiate diseased tissue while minimizing damage to healthy cells. For effective treatment, the linear energy transfer (LET) is a key parameter in ensuring the destruction of diseased cells, and both the dose and LET are typically represented as functions of depth. The distribution of dose and LET in the target depends on the beam properties, including beam energy, energy spread, beam size, and beam emittance. The aim of this work is to present the method used to characterize the proton beam properties obtained from the machine employed in the simulation and to determine the dose and dose-averaged LET (LET<sub>d</sub>) values, including their peak positions in depth. These results are used to predict the dose and LET<sub>d</sub> at different depth positions under experimental conditions. We utilized GEANT4, a Monte Carlo (MC) simulation-based software, to examine the integral depth-dose position and the peak position of the LET<sub>d</sub>. The proton source was obtained from a cyclotron accelerator, specifically the Varian ProBeam Compact spot scanning system at King Chulalongkorn Memorial Hospital in Bangkok, Thailand. The system provides proton energies ranging from 70 MeV to 220 MeV. In this study, four proton energies—70 MeV, 100 MeV, 150 MeV, and 220 MeV—were chosen to characterize the beam properties. The 80%–20% distal fall-off obtained from the simulation was used to determine the energy spread for each selected energy by matching the depth-dose peak with the measurement data. The optimal energy spreads were found to be 1.5%, 1.25%, 1%, and 0.5% for proton energies of 70 MeV, 100 MeV, 150 MeV, and 220 MeV, respectively. These energy spreads ensure that the difference in the depth-dose profile is below 1% when comparing the simulated and measured depth-dose profiles. Furthermore, the peak LET<sub>d</sub> was found to be approximately 1 mm away from the R<sub>80</sub> position, a depth that corresponds to 80% of maximum dose, for each energy. This information can be used to guide the desired LET<sub>d</sub> position by utilizing the R<sub>80</sub> depth position. |
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| ISSN: | 2076-3417 |