| Yang Jingzhe,Li Junli,Qiu Rui,Yi Hongchang,Wu Zhen.Study on microdosimetry for carbon ion radiotherapy[J].Chinese Journal of Radiological Medicine and Protection,2021,41(10):758-764 |
| Study on microdosimetry for carbon ion radiotherapy |
| Received:January 21, 2021 |
| DOI：10.3760/cma.j.issn.0254-5098.2021.10.007 |
| KeyWords:Carbon ion beam Microdosimetric spectrum Silicon on insulator microdosimetry Relative biological effectiveness |
| FundProject:国家自然科学基金（11875036） |
| Author Name | Affiliation | E-mail | | Yang Jingzhe | Department of Engineering Physics, Tsinghua University, Beijing 100084, China | | | Li Junli | Department of Engineering Physics, Tsinghua University, Beijing 100084, China | lijunli@mail.tsinghua.edu.cn | | Qiu Rui | Department of Engineering Physics, Tsinghua University, Beijing 100084, China | | | Yi Hongchang | Department of Engineering Physics, Tsinghua University, Beijing 100084, China | | | Wu Zhen | Department of Engineering Physics, Tsinghua University, Beijing 100084, China | |
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| Abstract:: |
| Objective To measure the microdosimetric spectrum of carbon ion beam and calculate the relative biological effect (RBE) distribution, so as to provide reference for radiotherapy microdosimetric research. Methods A silicon on insulator (SOI) microdosimeter was used to measure the microdosimetric spectrum of 12C ion beam, at 260 MeV/u, provided by Lanzhou Heavy Ion Accelerator National Laboratory. The measured pulse amplitude spectrum was converted to obtain the dose distribution. The microdosimetric spectra and RBE values at different polymethyl methacrylate depths were measured by the combination of different thickness PMMA. Results The microdosimetric spectra of 12C ion beam at 260 MeV/u were measured at different PMMA depths, and the relationship between dose line energy yD and RBE and different PMMA depths was also obtained. The measurement result showed that the RBE value reached a peak of 2.6 at the PMMA depth of 116.5 mm, and decreased rapidly after the Bragg peak. However, the RBE value was still 1.3 at the trailing point, which was about twice as much as the entrance of the flat zone. Conclusions This paper provides basic data for carbon ion beam microdosimetric spectroscopy through measurement. The RBE value of 12C ion beam gradually rises and reaches a peak with the increase of PMMA depth. After the Bragg peak position, it drops rapidly, but the biological effect at the tail cannot be ignored. At the same time, it reflects the dose fraction caused by different line energy intervals, and provides a reference for assessing the risk of heavy ion therapy for secondary cancer. |
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