FLASH radiotherapy using high-energy X-rays: Current status of PARTER platform in FLASH research

• Published in: Radiotherapy and oncology 2024-01, Vol.190, p.109967, Article 109967
• Main Authors: 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
• Format: Article
• Language: English
• Subjects: Beam monitoring; Dosimetry; FLASH radiotherapy; Megavoltage X-ray; PARTER platform
• ISSN: 0167-8140; 1879-0887; 1879-0887
• DOI: 10.1016/j.radonc.2023.109967

•The first high-energy X-ray FLASH radiotherapy platform (PARTER) has been upgraded.•6–8 MVs X-ray is available for FLASH irradiation at dose rate of 40–1000 Gy/s.•Treatment system and dosimetry were improved to provide verified high-performance FLASH X-rays.•The FLASH effect was demonstrated by numerous experiments using PARTER’s MV X-rays.•The accelerator is being upgraded for FLASH irradiation at 80-cm SSD at the end of 2025. 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 requiremen