Baikalov Alexander, Tho Daline, Liu Kevin, Bartzsch Stefan, Beddar Sam, Schüler Emil
Department of Radiation Physics, University of Texas MD Anderson Cancer Center; Department of Radiation Oncology, School of Medicine and Klinikum rechts der Isar, Technical University of Munich, Munich, Germany; Institute of Radiation Medicine, Helmholtz Zentrum München GmbH, German Research Center for Environmental Health, Neuherberg, Germany.
Department of Radiation Physics, University of Texas MD Anderson Cancer Center.
Int J Radiat Oncol Biol Phys. 2025 Apr 1;121(5):1372-1383. doi: 10.1016/j.ijrobp.2024.11.092. Epub 2024 Nov 28.
Scintillation dosimetry has promising qualities for ultra-high-dose-rate (UHDR) radiation therapy (RT), but no system has shown compatibility with mean dose rates (DR¯) above 100 Gy/s and doses per pulse (D) exceeding 1.5 Gy typical of UHDR (FLASH)-RT. The aim of this study was to characterize a novel scintillation dosimetry system with the potential of accommodating UHDRs.
We undertook a thorough dosimetric characterization of the system on an UHDR electron beamline. The system's response as a function of dose, DR¯, D, and the pulse dose-rate (DR) was investigated, as was the system's dose sensitivity (signal per unit dose) as a function of dose history. The capabilities of the system for time-resolved dosimetric readout were also evaluated.
Within a tolerance of ±3%, the system exhibited dose linearity and was independent of DR¯ and D within the tested ranges of 1.8 to 1341 Gy/s and 0.005 to 7.68 Gy, respectively. A 6% reduction in the signal per unit dose was observed as DR was increased from 8.9e4 to 1.8e6 Gy/s. The dose delivered per integration window of the continuously sampling photodetector had to remain between 0.028 and 11.56 Gy to preserve a stable signal response per unit dose. The system accurately measured D of individual pulses delivered at up to 120 Hz. The day-to-day variation of the signal per unit dose in a reference setup varied by up to ±13% but remained consistent (<±2%) within each treatment day and showed no signal loss as a function of dose history.
With daily calibrations and DR-specific correction factors, the system reliably provides real-time, millisecond-resolved dosimetric measurements of pulsed conventional and UHDR beams from typical electron linacs, marking an important advancement in UHDR dosimetry and offering diverse applications to FLASH-RT and related fields.
闪烁剂量测定法在超高剂量率（UHDR）放射治疗（RT）方面具有良好的特性，但尚无系统显示出与高于100 Gy/s的平均剂量率（DR¯）以及超过1.5 Gy的单脉冲剂量（D）兼容，而这是UHDR（FLASH）-RT的典型特征。本研究的目的是对一种具有适应UHDR潜力的新型闪烁剂量测定系统进行特性描述。
我们在一条UHDR电子束线上对该系统进行了全面的剂量学特性描述。研究了系统响应作为剂量、DR¯、D和脉冲剂量率（DR）的函数，以及系统剂量灵敏度（单位剂量信号）作为剂量历史的函数。还评估了系统进行时间分辨剂量学读出的能力。
在±3%的公差范围内，该系统呈现剂量线性，并且在分别为1.8至1341 Gy/s和0.005至7.68 Gy的测试范围内与DR¯和D无关。当DR从8.9e4增加到1.8e6 Gy/s时，观察到单位剂量信号降低了6%。连续采样光电探测器的每个积分窗口输送的剂量必须保持在0.028至11.56 Gy之间，以保持单位剂量的稳定信号响应。该系统准确测量了高达120 Hz时单个脉冲的D。在参考设置中，单位剂量信号的每日变化高达±13%，但在每个治疗日内保持一致（<±2%），并且未显示出作为剂量历史函数的信号损失。
通过每日校准和特定于DR的校正因子，该系统可靠地提供来自典型电子直线加速器的脉冲传统和UHDR束的实时、毫秒分辨剂量学测量，标志着UHDR剂量测定法的一项重要进展，并为FLASH-RT及相关领域提供了多种应用。
