Abstract
The purpose was to perform beam modeling and plan verification for uniform scanned (US) carbon ion therapy delivered by Heavy Ion Medical Machine (HIMM). As the field inhomogeneity is larger than the commonly accepted 3% gamma pass rate criteria, a simple flat broad beam model is no longer accurate. A modified broad beam model accounting for field inhomogeneity was proposed and validated. The commissioning process for automatic beam modeling was described. Characteristic lateral dose distributions were collected at different depths for each field combination. The field inhomogeneities were modeled as two-dimensional interpolations of the lateral dose data. Dose calculation was based on ray-tracing combined with an asymmetric double-sigmoid function describing the dose at field edge. Two types of plan verifications on three US nozzles were carried out: 1) without range compensators 2) with range compensators. The distance-to-agreement at distal fall-off was within 1 mm. The absolute dose calibration was within 1.9% and the mean value was 0.6 (±0.5%). The verification plans satisfied 95% pass rate based on 3mm/3% gamma analysis for all three nozzles. Comparison with literature suggested a clinical factor of 1.33. The modified broad beam model satisfied the gamma analysis requirement and could be used for commissioning carbon US beams.
Data availability
The datasets used and analyzed during the current study are available from the corresponding author on reasonable request.
References
Kanai, T. et al. Irradiation of mixed beam and design of spread-out Bragg peak for heavy-ion radiotherapy. Radiat. Res. 147, 78–85. https://doi.org/10.2307/3579446 (1997).
Moyers, M. F. & Vatnitsky, S. M. Practical Implementation of Light Ion Beam Treatments (Medical Physics Publishing, 2012).
Li, Q. et al. Progress in heavy ion cancer therapy at imp and future development. Malignancy Spectrum 1, 91–98. https://doi.org/10.1002/msp2.22 (2024).
Matsubara, H. et al. Comparison of passive and scanning irradiation methods for carbon-ion radiotherapy for breast cancer. J. Radiat. Res. 59, 625–631. https://doi.org/10.1093/jrr/rry052 (2018).
Karube, M. et al. Carbon-ion pencil beam scanning for thoracic treatment - initiation report and dose metrics evaluation. J. Radiat. Res. 57, 576–581. https://doi.org/10.1093/jrr/rrw057. https://academic.oup.com/jrr/article-pdf/57/5/576/31614611/rrw057.pdf (2016).
Sato, K., Miyamoto, A., Kameda, D. & Takayama, S. Carbon-ion synchrotron accelerator and raster scanning irradiation system. In Advances in Accelerators and Medical Physics. 111–127. https://doi.org/10.1016/B978-0-323-99191-9.00018-9 (Academic Press, 2023).
Kanematsu, N. et al. Treatment planning for the layer-stacking irradiation system for three-dimensional conformal heavy-ion radiotherapy. Med. Phys. 29, 2823–2829. https://doi.org/10.1118/1.1521938 (2002).
Futami, Y. et al. Broad-beam three-dimensional irradiation system for heavy-ion radiotherapy at Himac. Nucl. Instrum. Methods Physics Res. Sect. A Acceler. Spectrom. Detect. Assoc. Equip. 430, 143–153. https://doi.org/10.1016/S0168-9002(99)00194-1 (1999).
Sakamoto, Y. et al. A robust optimization method for weighted-layer-stacking proton beam therapy. Phys. Med. Biol. 65. https://doi.org/10.1088/1361-6560/ab9efd (2020).
Endo, M. Hiplan—A heavy ion treatment planning system at Himac. J. Jpn. Soc. Ther. Radiol. Oncol. 8, 231–238. https://jglobal.jst.go.jp/en/detail?JGLOBAL_ID=200902131446109757 (1996) .
Tomura, H. et al. Analysis of the penumbra for uniform irradiation fields delivered by a Wobbler method. Jpn. J. Med. Phys. 18, 42–56. https://doi.org/10.11323/jjmp1992.18.1_42 (1998).
Torikoshi, M. & Minohara, S. Irradiation system for Himac. Tech. Rep. https://doi.org/10.1269/jrr.48.a15 (2007).
RaySearch Laboratories. RayStation User Manual. (RaySearch Laboratories, 2023).
Inaniwa, T. et al. Reformulation of a clinical-dose system for carbon-ion radiotherapy treatment planning at the National Institute of Radiological Sciences, Japan. Phys. Med. Biol. 60, 3271–3286. https://doi.org/10.1088/0031-9155/60/8/3271 (2015).
Yonai, S. et al. Evaluation of beam wobbling methods for heavy-ion radiotherapy. Med. Phys. 35, 927–938. https://doi.org/10.1118/1.2836953 (2008).
Zhang, H. et al. A novel pencil beam model for carbon-ion dose calculation derived from Monte Carlo simulations. Phys. Med. 55, 15–24. https://doi.org/10.1016/j.ejmp.2018.10.014 (2018).
Fujitaka, S. et al. Physical and biological beam modeling for carbon beam scanning at Osaka Heavy Ion Therapy Center. J. Appl. Clin. Med. Phys. 22, 77–92. https://doi.org/10.1002/acm2.13262 (2021).
Abou-Haïdar, Z., Alvarez, M. A. G., Espino, J. M., Gallardo, M. I. & Nieto, F. J. P. Output factor determination for dose measurements in axial and perpendicular planes using a silicon strip detector. Phys. Rev. Acc. Beams 15, 42802–42802. https://doi.org/10.1103/PhysRevSTAB.15.042802 (2012).
McMahon, S. J. The linear quadratic model: Usage, interpretation and challenges. Phys Med. Biol. 64. https://doi.org/10.1088/1361-6560/aaf26a (2019).
Liu, X., Li, Q. & Dai, Z. Dose calculation methods in heavy ion cancer therapy at imp. Nucl. Phys. Rev. 26, 69–75. https://doi.org/10.11804/NuclPhysRev.26.01.069 (2009).
Allison, J. et al. Recent developments in geant4. Nucl. Instrum. Methods Phys. Res. Sect. A Acc. Spectrom. Detect. Assoc. Equip. 835, 186–225. https://doi.org/10.1016/j.nima.2016.06.125 (2016).
Acknowledgements
The author would like to thank the HIMM engineering and maintenance team for their assistance with data collection.
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Yunzhou Xia conceived the study, developed the methodology, conducted the investigation, performed formal analysis, curated the data, created visualizations, wrote the original draft, and reviewed and edited the manuscript.
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Yunzhou Xia is an employee of CAS Ion Medical Technology Co. Ltd., which is involved in the development of carbon ion treatment planning systems. This employment may be perceived as a potential conflict of interest. The author declares that the scientific conclusions of this manuscript were developed independently and are not influenced by the commercial interests of the company.
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Xia, Y. A modified broad beam model for uniformly scanned carbon ion therapy accounting for field inhomogeneities. Sci Rep (2026). https://doi.org/10.1038/s41598-026-39619-9
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DOI: https://doi.org/10.1038/s41598-026-39619-9
