背景:评估FLASH放射治疗在人类中的可行性的第一个临床试验已经开始(FAST-01,FAST-02),并且可以预见更多的试验。为了增加试验之间的可比性,重要的是确保治疗质量,因此建立机器质量保证(QA)标准。目前,AAPMTG-224报告被认为是质子治疗机器QA的标准,然而,它不打算用于超高剂量率(UHDR)质子束,由于对FLASH效应的观察,它们获得了兴趣。
目的:本研究的目的是就需要QA的传输模式下UHDR质子束的机器QA的实用指南达成共识,他们应该如何做,哪些检测器适用于UHDR机器QA,以及应该应用什么公差限制。
方法:一个国际医学物理学家小组进行了风险评估,以确定当前机器QA标准的差距。基于此,提出了如何对UHDR质子束执行机器QA的实用指南。
结果:风险评估清楚地确定了对时间剂量学的额外指导的需要,寻址剂量率(恒定性),剂量溢出,和扫描速度。此外,确定了AAPMTG-224的几个微小变化;定义所需的剂量率水平,临床相关剂量水平的使用,以及使用适应的光束设置,以最大程度地减少检测器和体模材料的激活或避免特定检测器的饱和效应。最终报告是在讨论和共识的基础上编写的。
结论:在基于同步回旋加速器的系统的透射模式下,UHDR扫描质子束所需的QA以及应如何执行方面达成共识。然而,小组讨论还表明,缺乏高时间分辨率的探测器和足够的质量保证数据来为一些拟议的质量保证程序设定适当的限制。
BACKGROUND: The first clinical trials to assess the feasibility of FLASH radiotherapy in humans have started (FAST-01, FAST-02) and more trials are foreseen. To increase comparability between trials it is important to assure treatment quality and therefore establish a standard for machine quality assurance (QA). Currently, the AAPM TG-224 report is considered as the standard on machine QA for proton therapy, however, it was not intended to be used for ultra-high dose rate (UHDR) proton beams, which have gained interest due to the observation of the FLASH effect.
OBJECTIVE: The aim of this study is to find
consensus on practical
guidelines on machine QA for UHDR proton beams in transmission mode in terms of which QA is required, how they should be done, which detectors are suitable for UHDR machine QA, and what tolerance limits should be applied.
METHODS: A risk assessment to determine the gaps in the current standard for machine QA was performed by an international group of medical physicists. Based on that, practical
guidelines on how to perform machine QA for UHDR proton beams were proposed.
RESULTS: The risk assessment clearly identified the need for additional guidance on temporal dosimetry, addressing dose rate (constancy), dose spillage, and scanning speed. In addition, several minor changes from AAPM TG-224 were identified; define required dose rate levels, the use of clinically relevant dose levels, and the use of adapted beam settings to minimize activation of detector and phantom materials or to avoid saturation effects of specific detectors. The final report was created based on discussions and
consensus.
CONCLUSIONS: Consensus was reached on what QA is required for UHDR scanning proton beams in transmission mode for isochronous cyclotron-based systems and how they should be performed. However, the group discussions also showed that there is a lack of high temporal resolution detectors and sufficient QA data to set appropriate limits for some of the proposed QA procedures.