| Qin Shirui,Wang Hong,Huan Fukui,et al.Methods for estimating the beam-on time of the Unity MR-Linac[J].Chinese Journal of Radiological Medicine and Protection,2026,46(6):587-591 |
| Methods for estimating the beam-on time of the Unity MR-Linac |
| Received:September 25, 2025 |
| DOI：10.3760/cma.j.cn112271-20250925-00343 |
| KeyWords:Magnetic resonance-guided linear accelerator|Beam-on time|Estimation |
| FundProject: |
| Author Name | Affiliation | E-mail | | Qin Shirui | Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100021, China | | | Wang Hong | Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100021, China | | | Huan Fukui | Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100021, China | | | Li Xiufen | Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100021, China | | | Sun Yingying | Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100021, China | | | Hong Tianhang | Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100021, China | | | Liu Fan | Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100021, China | | | Tian Yuan | Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100021, China | tianyuan1981@hotmail.com |
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| Abstract:: |
| Objective To investigate the impacts of various factors in adaptive radiotherapy plans on the beam-on time of Unity—a magnetic resonance-guided linear accelerator (MR-Linac)—using [BFQ]two different method and to estimate the beam-on time in clinical radiotherapy. These efforts are aimed at providing a reference for clinical utilization of the Unity MR-Linac. Methods Formulas for estimating the beam-on time were developed using two method: fitting through stepwise regression and component-based calculation. To develop the fitted formula, a retrospective analysis was conducted on the clinical data from 174 patients treated using the Unity MR-Linac at the department of radiation oncology, Cancer Hospital, Chinese Academy of Medical Sciences, from July 2023 to September 2024. These clinical data comprised the beam-on time (T) of the total 1 112 fractions, as well as the radiotherapy plan parameters corresponding to various fractions, including the number of irradiation fields (B), the total number of irradiation subfields (S), the total number of monitor units (MUs) of plans, the gantry angle range (ΔGA), and the fractional dose (FD). The correlations between various influencing factors and T were analyzed using Spearman's rank correlation. Then, the mathematical formula of T and parameters strongly correlated with T were fitted through linear regression. For the component-based calculation method, T was the sum of three parts: radiation exposure time, gantry rotation time, and the formation time of subfields. The accuracy of both established formulas was validated using data from 145 radiotherapy fractions of another 23 patients treated during the aforementioned period. Results The fitted formula was T=0.140MU+3.781S, with a coefficient of determination (R2) of 0.998. The conformity deviation, expressed as (x±s), was determined at 0.86%±4.00%. In contrast, the formula derived through component-based calculation was T=0.143MU-0.073B2+1.067B+3.582S+11.153, with a onformity deviation of 2.97% ±4.56%. Conclusions Primary factors influencing the beam-on time of the Unity MR-Linac include S and MU in adaptive radiotherapy plans. In the case where clinical dose requirements are satisfied, reducing S and MU can significantly shorten the beam-on time. In contrast, increasing B can improve the quality of adaptive radiotherapy plans without excessively prolonging the beam-on time. The formulas derived using the two method exhibit minimal statistically significant differences when used to verify the beam-on time. |
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