Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, United States of America.
Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT 06510, United States of America.
Phys Med Biol. 2022 Aug 5;67(16). doi: 10.1088/1361-6560/ac8269.
. Irradiation with ultra-high dose rates (>40 Gy s), also known as FLASH irradiation, has the potential to shift the paradigm of radiation therapy because of its reduced toxicity to normal tissues compared to that of conventional irradiations. The goal of this study was to (1) achieve FLASH irradiation conditions suitable for pre-clinicalandbiology experiments using our synchrotron-based proton beamline and (2) commission the FLASH irradiation conditions achieved.. To achieve these suitable FLASH conditions, we made a series of adaptations to our proton beamline, including modifying the spill length and size of accelerating cycles, repurposing the reference monitor for dose control, and expanding the field size with a custom double-scattering system. We performed the dosimetric commissioning with measurements using an Advanced Markus chamber and EBT-XD films as well as with Monte Carlo simulations.. Through adaptations, we have successfully achieved FLASH irradiation conditions, with an average dose rate of up to 375 Gy s. The Advanced Markus chamber was shown to be appropriate for absolute dose calibration under our FLASH conditions with a recombination factor ranging from 1.002 to 1.006 because of the continuous nature of our synchrotron-based proton delivery within a spill. Additionally, the absolute dose measured using the Advanced Markus chamber and EBT-XD films agreed well, with average and maximum differences of 0.32% and 1.63%, respectively. We also performed a comprehensive temporal analysis for FLASH spills produced by our system, which helped us identify a unique relationship between the average dose rate and the dose in our FLASH irradiation.We have established a synchrotron-based proton FLASH irradiation platform with accurate and precise dosimetry that is suitable for pre-clinical biology experiments. The unique time structure of the FLASH irradiation produced by our synchrotron-based system may shed new light onto the mechanism behind the FLASH effect.
. 超高剂量率（>40 Gy s）照射，也称为 FLASH 照射，由于与常规照射相比对正常组织的毒性降低，因此有可能改变放射治疗的模式。本研究的目的是：(1) 使用我们基于同步加速器的质子束线实现适用于临床前和生物学实验的 FLASH 照射条件；(2) 验证所实现的 FLASH 照射条件。为了实现这些合适的 FLASH 条件，我们对质子束线进行了一系列的调整，包括修改散裂长度和加速周期的大小、重新利用参考监视器进行剂量控制以及使用定制的双散射系统扩展射野。我们使用先进的 Markus 室和 EBT-XD 胶片进行剂量学验证，并结合蒙特卡罗模拟进行测量。通过调整，我们成功地实现了 FLASH 照射条件，平均剂量率高达 375 Gy s。由于我们基于同步加速器的质子输送在散裂期间具有连续的性质，先进的 Markus 室显示出适用于我们 FLASH 条件下的绝对剂量校准，重组因子在 1.002 到 1.006 之间。此外，使用先进的 Markus 室和 EBT-XD 胶片测量的绝对剂量非常吻合，平均和最大差异分别为 0.32%和 1.63%。我们还对我们系统产生的 FLASH 散裂进行了全面的时间分析，这有助于我们确定我们 FLASH 照射中的平均剂量率和剂量之间的独特关系。我们已经建立了一个基于同步加速器的质子 FLASH 照射平台，具有准确和精确的剂量学，适用于临床前生物学实验。我们基于同步加速器的系统产生的 FLASH 照射的独特时间结构可能为 FLASH 效应背后的机制提供新的见解。
