Technical note: Validation of an ultrahigh dose rate pulsed electron beam monitoring system using a current transformer for FLASH preclinical studies.
Technical note: Validation of an ultrahigh dose rate pulsed electron beam monitoring system using a current transformer for FLASH preclinical studies.
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Oriatron eRT6 是一款用于 FLASH 临床前研究的直线加速器 (linac)，能够达到从常规 (CONV) 到超高 (UHDR) 的剂量率。这项工作描述了商用束电流互感器 (BCT) 作为与 CONV 和 UHDR 辐照兼容的在线监测工具的实施，用于临床前 FLASH 研究。使用两个 BCT 来测量 Oriatron eRT6 直线加速器的输出。首先，检查设定的标称光束参数与 BCT 测量的光束参数之间的对应关系。然后，我们建立了总出口电荷（通过 BCT 测量）与水吸收剂量之间的关系。表征了 UHDR 下脉冲宽度 (PW) 和脉冲重复频率 (PRF) 的影响，以及 CONV 和 UHDR 下出射电荷与剂量之间关系的短期和长期稳定性。 BCT 能够一致地确定脉冲数、PW 和 PRF。对于固定 PW 和脉冲高度，从 BCT 测量的出射电荷与剂量相关，并且在 CONV 和 UHDR 模式下发现线性关系，不确定性分别为 0.5% 和 3%。剂量电荷比的短期和长期稳定性低于 1.6%。我们实施了商用 BCT，并展示了它们作为在线光束监测系统的能力，以支持 CONV 和 UHDR 照射的 FLASH 临床前研究。实施的 BCT 支持剂量测量，突出显示连续多次测量之间的变化，能够监测用于照射的物理参数，并且是 FLASH 放射治疗临床转化安全的重要一步。
The Oriatron eRT6 is a linear accelerator (linac) used in FLASH preclinical studies able to reach dose rates ranging from conventional (CONV) up to ultrahigh (UHDR). This work describes the implementation of commercially available beam current transformers (BCTs) as online monitoring tools compatible with CONV and UHDR irradiations for preclinical FLASH studies. Two BCTs were used to measure the output of the Oriatron eRT6 linac. First, the correspondence between the set nominal beam parameters and those measured by the BCTs was checked. Then, we established the relationship between the total exit charge (measured by BCTs) and the absorbed dose to water. The influence of the pulse width (PW) and the pulse repetition frequency (PRF) at UHDR was characterized, as well as the short‐ and long‐term stabilities of the relationship between the exit charge and the dose at CONV and UHDR. The BCTs were able to determine consistently the number of pulses, PW, and PRF. For fixed PW and pulse height, the exit charge measured from BCTs was correlated with the dose, and linear relationships were found with uncertainties of 0.5 % and 3 % in CONV and UHDR mode, respectively. Short‐ and long‐term stabilities of the dose‐to‐charge ratio were below 1.6 %. We implemented commercially available BCTs and demonstrated their ability to act as online beam monitoring systems to support FLASH preclinical studies with CONV and UHDR irradiations. The implemented BCTs support dosimetric measurements, highlight variations among multiple measurements in a row, enable monitoring of the physics parameters used for irradiation, and are an important step for the safety of the clinical translation of FLASH radiation therapy.