Yang Yiwei, Wang Jianxin, Gao Feng, Liu Zhen, Dai Tangzhi, Zhang Haowen, Zhu Hongyu, Wang Tingting, Xiao Dexin, Zhou Kui, Zhou Zheng, Wu Dai, Du Xiaobo, Bai Sen
Institute of Applied Electronics, China Academy of Engineering Physics, Mianyang 621900, China.
Department of Oncology, NHC Key Laboratory of Nuclear Technology Medical Transformation (Mianyang Central Hospital), Mianyang Central Hospital, School of Medicine, University of Electronic Science and Technology, Mianyang 621000, China.
Radiother Oncol. 2023 Oct 27:109967. doi: 10.1016/j.radonc.2023.109967.
Recent studies indicated that ultrahigh dose rate (FLASH) radiation can reduce damage to normal tissue while maintaining anti-tumour activity compared to conventional dose rate (CONV) radiation. This paper provides a comprehensive description of the current status of the Platform for Advanced Radiotherapy Research (PARTER), which serves as the first experimental FLASH platform utilizing megavoltage X-rays and has facilitated numerous experiments.
PARTER was established in 2019 based on a superconducting linac to support experimental FLASH studies using megavoltage X-rays. Continuous upgrades have been made to the accelerator, collimators, flattening filters, monitors, other auxiliary devices, and irradiation process in order to achieve optimal results. Passive and active dosimeters are employed for measuring dose distribution and to ensure traceability of radiation doses.
The dose monitors and dosimeters demonstrate reliable performance with acceptable stability. At PARTER, the maximum mean dose rate is approximately 400 Gy/s at a surface-source distance of 20 cm (over 1000 Gy/s at smaller distances), with an instantaneous dose rate of approximately 8E5 Gy/s. Both passive and active dosimeters exhibit good linearity and agreement during FLASH X-ray irradiation. The monitors show good linearity to dose rate, with short-term fluctuations within 1.5% for the diamond monitor. The discrepancy between measured absorbed dose and dose protocol is typically less than 4%. The X-ray energy spectra on PARTER are comparable to those for megavoltage CONV linacs operating in flattening filter-free mode. The maximum field size of the FLASH beam is 4.5 cm × 4.5 cm. The FLASH dose profile demonstrates satisfactory flatness (1.04) and similar penumbra compared to clinical CONV linac, while the percentage depth dose curve of FLASH X-rays is steeper than that of the clinical megavoltage CONV X-ray.
PARTER represents a pioneering platform for conducting megavolts FLASH X-ray irradiation in biological experiments. It effectively fulfills the requirements of preclinical research on megavoltage X-ray FLASH and undergoes continuous upgrades to meet increasingly demanding performance criteria.
近期研究表明，与传统剂量率（CONV）辐射相比，超高剂量率（FLASH）辐射在保持抗肿瘤活性的同时可减少对正常组织的损伤。本文全面描述了先进放射治疗研究平台（PARTER）的现状，该平台是首个利用兆伏级X射线的实验性FLASH平台，并推动了众多实验。
PARTER于2019年基于超导直线加速器建立，以支持使用兆伏级X射线的实验性FLASH研究。对加速器、准直器、均整滤过器、监测器、其他辅助设备以及辐照过程进行了持续升级，以实现最佳效果。采用被动和主动剂量计测量剂量分布并确保辐射剂量的可追溯性。
剂量监测器和剂量计表现出可靠的性能和可接受的稳定性。在PARTER，在表面源距离为20 cm时最大平均剂量率约为400 Gy/s（在较小距离时超过1000 Gy/s），瞬时剂量率约为8E5 Gy/s。被动和主动剂量计在FLASH X射线辐照期间均表现出良好的线性和一致性。监测器对剂量率表现出良好的线性，金刚石监测器的短期波动在1.5%以内。测量的吸收剂量与剂量方案之间的差异通常小于4%。PARTER上的X射线能谱与在无均整滤过模式下运行的兆伏级CONV直线加速器的能谱相当。FLASH束的最大射野尺寸为4.5 cm×4.5 cm。FLASH剂量分布显示出令人满意的平坦度（1.04），与临床CONV直线加速器相比半影相似，而FLASH X射线的百分深度剂量曲线比临床兆伏级CONV X射线的更陡。
PARTER是在生物实验中进行兆伏级FLASH X射线辐照的开创性平台。它有效地满足了兆伏级X射线FLASH临床前研究的要求，并不断升级以满足日益严格的性能标准。
