@misc{oai:repo.qst.go.jp:00084422,
 author = {Urago, Yuka and Sakama, Makoto and Katayose, Tetsurou and Chang, Weishan and Yuka, Urago and Makoto, Sakama and Chang, Weishan},
 month = {Sep},
 note = {Background:
In IAEA TRS-398, the uncertainty of the absorbed dose to water Dw for carbon-ion beams is estimated to be over 3 %, which is larger than photons and protons. The standard uncertainty of the beam quality correction factor ????Q, a component of Dw, for carbon-ion beams is estimated to be 2.8 % for the cylindrical chambers and 3.2 % for the plane-parallel chambers. Therefore, ????Q is the dominant factor in the uncertainty of Dw. Calorimetry has been performed recently to reduce this uncertainty of ????Q in carbon-ion beams. However, the calorimetry condition is limited and the calorimetry results will need to be verified for consistency in the dosimetry chain data. Systematically estimated ????Q using MC simulation can make up for the shortcoming while it has hardly ever been reported. In this study, ????Q of 6 type ionization chambers for carbon-ion beams were evaluated using experimental measurements and MC simulations.
Methods:
The ????Q for each chamber was evaluated by 2 processes: measurements in QST-HIMAC in Japan and simulations with Geant4 ver. 10.2.p03. For the measurements, Dw in 60Co gamma-ray and 290 MeV/u-12C beams were measured using the subjected chambers and the reference chamber (PTW 30011) for obtaining ????Q ratio for each chamber of interest. For the simulations, absorbed dose to air in the sensitive volume of each chamber and the absorbed dose to water were calculated to acquire fQ, which is the product of the water-to-air stopping power ratio and the chamber-specific perturbation correction factor. The ????Q was calculated with fQ (simulations) and Wair (literature value).
Results:
The calculated ????Q ratios between the subjected chamber and the reference chamber showed good agreement with the measured ????Q ratios. The differences between the currently recommended ????Q in TRS-398 and calculated ????Q were 0.4 % for the cylindrical chambers and 0.9 % for the plane-parallel chambers at the maximum, respectively. The uncertainty of calculated ????Q was decreased by more than 1 % compared with 3 % at TRS-398.
Conclusion:
It was shown that it is possible to calculate ????Q for carbon-ion beams with high accuracy by MC simulations using Geant4., The 9th Korea-Japan Joint Meeting on Medical Physics},
 title = {Evaluation of Monte Carlo calculated beam quality correction factors for several ionization chamber types in carbon-ion beams},
 year = {2021}
}