Clinical dose assessment for scanned carbon-ion radiotherapy using linear energy transfer measurements and Monte Carlo simulations

Taku Nakaji; Tatsuaki Kanai; Masaaki Takashina; Akihiko Matsumura; Kohei Osaki; Masashi Yagi; Toshiro Tsubouchi; Noriaki Hamatani; Kazuhiko Ogawa

doi:10.1088/1361-6560/aca003

Clinical dose assessment for scanned carbon-ion radiotherapy using linear energy transfer measurements and Monte Carlo simulations

Phys Med Biol. 2022 Dec 15;67(24). doi: 10.1088/1361-6560/aca003.

Authors

Taku Nakaji^{1

2}, Tatsuaki Kanai^{2

3}, Masaaki Takashina^{2

3}, Akihiko Matsumura⁴, Kohei Osaki⁵, Masashi Yagi^{2

3}, Toshiro Tsubouchi³, Noriaki Hamatani³, Kazuhiko Ogawa²

Affiliations

¹ QST Hospital, Quantum Life and Medical Science Directorate, National Institutes for Quantum Science and Technology (QST), 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan.
² Graduate School of Medicine, Osaka University, 2-2 Yamada-oka, Suita, Osaka 565-0871, Japan.
³ Division of Medical Physics, Osaka Heavy Ion Therapy Center, 3-1-10 Otemae, Chuo-ku, Osaka City, Osaka 540-0008, Japan.
⁴ Heavy Ion Medical Center, Gunma University, 3-39-22 Showa-Machi, Maebashi, Gunma 371-8511, Japan.
⁵ Graduate School of Medicine, Gunma University, 3-39-22 Showa-Machi, Maebashi, Gunma 371-8511, Japan.

PMID: 36327456
DOI: 10.1088/1361-6560/aca003

Abstract

Objective. Dosimetric commissioning of treatment planning systems (TPS) focuses on validating the agreement of the physical dose with experimental data. For carbon-ion radiotherapy, the commissioning of the relative biological effectiveness (RBE) is necessary to predict the clinical outcome based on the radiation quality of the mixed radiation field. In this study, we proposed a approach for RBE commissioning using Monte Carlo (MC) simulations, which was further strengthen by RBE validation based on linear energy transfer (LET) measurements.Approach. First, we tuned the MC simulation based on the results of dosimetric experiments including the beam ranges, beam sizes, and MU calibrations. Furthermore, we compared simulated results to measured depth- and radial-LET distributions of the 430 MeV u^-1carbon-ion spot beam with a 1.5 mm², 36μm thick silicon detector. The measured dose-averaged LET (LET_d) and RBE were compared with the simulated results. The RBE was calculated based on the mixed beam model with linear-quadratic parameters depending on the LET. Finally, TPS-calculated clinical dose profiles were validated through the tuned MC-based calculations.Main results. A 10 keVμm^-1and 0.15 agreement for LET_dand RBE, respectively, were found between simulation and measurement results obtained for a 2σlateral size of 430 MeV u^-1carbon-ion spot beam in water. These results suggested that the tuned MC simulation can be used with acceptable precision for the RBE and LET calculations of carbon-ion spot beam within the clinical energy range. For physical and clinical doses, the TPS- and MC-based calculations showed good agreements within 1.0% at the centre of the spread-out Bragg peaks.Significance. The tuned MC simulation can accurately reproduce the actual carbon-ion beams, and it can be used to validate the physical and clinical dose distributions calculated by TPS. Moreover, the MC simulation can be used for dosimetric commissioning, including clinical doses, without LET measurements.

Keywords: LET measurements; Monte Carlo simulation; RBE; carbon-ion radiotherapy; mixed beam model; silicon detector.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Carbon / therapeutic use
Linear Energy Transfer*
Monte Carlo Method
Proton Therapy* / methods
Radiometry
Radiotherapy Planning, Computer-Assisted / methods
Relative Biological Effectiveness

Substances

Carbon