Calorimeter for Real-Time Dosimetry of Pulsed Ultra-High Dose Rate Electron Beams
Calorimeter for Real-Time Dosimetry of Pulsed Ultra-High Dose Rate Electron Beams
复制标题
DOI：
10.3389/fphy.2020.567340
复制
发表时间：
2020-10-30
影响因子：
3.1
通讯作者：
McEwen, Malcolm
中科院分区：
文献类型：
--
作者：
Bourgouin, Alexandra;Schueller, Andreas;McEwen, Malcolm
研究了一种铝量热计作为一种可能的实时剂量计，用于每脉冲超高剂量（DPP）的电子束，如FLASH放射治疗（几Gy/脉冲）。电离室是传统外束放射治疗中应用最广泛的主动剂量计类型，在这些条件下离子重组损失很大。被动剂量计，如丙氨酸，与剂量率无关，但不提供实时读数。在研究的超高DPP范围内（高达2.3 Gy/脉冲），丙氨酸的响应与DPP无关。在超高DPP条件下，利用丙氨酸剂量测量确定了先进Markus平面平行电离室的离子重组校正。离子收集损失大于50%。因此，电离室被认为不适合用于FLASH放射治疗的精确剂量测定。作为替代方案，在第二个（独立）实验中，研究了在超高DPP电子辐射下以准绝热模式工作的铝制开放式大气量热计。在0.3 ~ 1.8 Gy/脉冲的DPP范围内，通过改变光束脉冲电荷和DPP来评估量热计响应的线性度。量热计响应的平均标准差为0.1%。响应与调查范围内的DPP成正比。量热计剂量随束流脉冲电荷的线性拟合的平均偏差为
An aluminum calorimeter was investigated as a possible real-time dosimeter for electron beams with an ultra-high dose per pulse (DPP), as used in FLASH radiation therapy (a few Gy/pulse). Ionization chambers, the most widely used active dosimeter type in conventional external beam radiation therapy, suffer from large ion recombination losses at these conditions. Passive dosimeters, such as alanine, are independent of dose rate but do not provide real-time read-out. In this work it is shown that the response of alanine is independent of the DPP in the investigated ultra-high DPP range (up to 2.3 Gy/pulse). Alanine dose measurements were then used to determine the ion recombination correction for an Advanced Markus plane-parallel ionization chamber at ultra-high DPP. Ion collection losses larger than 50% were observed. Therefore, ionization chambers are not considered suitable for accurate dosimetry in FLASH radiation therapy. As an alternative, in a second (independent) experiment an aluminum open-to-atmosphere calorimeter, operated in the quasi-adiabatic mode was investigated at ultra-high DPP electron radiation. The beam pulse charge, and thus the DPP, was varied to evaluate the linearity of the calorimeter response in the DPP range between 0.3 and 1.8 Gy/pulse. On average, the standard deviation of the calorimeter response was 0.1%. The response was proportional to the DPP in the investigated range. The average deviation of the linear fit of the calorimeter dose as a function of the beam pulse charge was