Abstract：
OBJECTIVE: To investigate quality assurance (QA) techniques for in vivo dosimetry and establish its routine uses for proton FLASH small animal experiments with a saturated monitor chamber.
METHODS: 227 mice were irradiated at FLASH or conventional (CONV) dose rates with a 250 MeV FLASH-capable proton beamline using pencil beam scanning to characterize the proton FLASH effect on abdominal irradiation and examining various endpoints. A 2D strip ionization chamber array (SICA) detector was positioned upstream of collimation and used for in vivo dose monitoring during irradiation. Before each irradiation series, SICA signal was correlated with the isocenter dose at each delivered dose rate. Dose, dose rate, and 2D dose distribution for each mouse were monitored with the SICA detector.
RESULTS: Calibration curves between the upstream SICA detector signal and the delivered dose at isocenter had good linearity with minimal R2 values of 0.991 (FLASH) and 0.985 (CONV), and slopes were consistent for each modality. After reassigning mice, standard deviations were less than 1.85 % (FLASH) and 0.83 % (CONV) for all dose levels, with no individual subject dose falling outside a ± 3.6 % range of the designated dose. FLASH fields had a field-averaged dose rate of 79.0 ± 0.8 Gy/s and mean local average dose rate of 160.6 ± 3.0 Gy/s. In vivo dosimetry allowed for the accurate detection of variation between the delivered and the planned dose.
CONCLUSIONS: In vivo dosimetry benefits FLASH experiments through enabling real-time dose and dose rate monitoring allowing mouse cohort regrouping when beam fluctuation causes delivered dose to vary from planned dose.
METHODS: 227 mice were irradiated at FLASH or conventional (CONV) dose rates with a 250 MeV FLASH-capable proton beamline using pencil beam scanning to characterize the proton FLASH effect on abdominal irradiation and examining various endpoints. A 2D strip ionization chamber array (SICA) detector was positioned upstream of collimation and used for in vivo dose monitoring during irradiation. Before each irradiation series, SICA signal was correlated with the isocenter dose at each delivered dose rate. Dose, dose rate, and 2D dose distribution for each mouse were monitored with the SICA detector.
RESULTS: Calibration curves between the upstream SICA detector signal and the delivered dose at isocenter had good linearity with minimal R2 values of 0.991 (FLASH) and 0.985 (CONV), and slopes were consistent for each modality. After reassigning mice, standard deviations were less than 1.85 % (FLASH) and 0.83 % (CONV) for all dose levels, with no individual subject dose falling outside a ± 3.6 % range of the designated dose. FLASH fields had a field-averaged dose rate of 79.0 ± 0.8 Gy/s and mean local average dose rate of 160.6 ± 3.0 Gy/s. In vivo dosimetry allowed for the accurate detection of variation between the delivered and the planned dose.
CONCLUSIONS: In vivo dosimetry benefits FLASH experiments through enabling real-time dose and dose rate monitoring allowing mouse cohort regrouping when beam fluctuation causes delivered dose to vary from planned dose.
摘要：
目的：研究体内剂量测定的质量保证（QA）技术，并建立其在具有饱和监测室的质子FLASH小动物实验中的常规用途。
方法：227只小鼠以FLASH或常规（CONV）剂量率用250MeV具有FLASH能力的质子束线进行照射，使用笔形束扫描表征质子FLASH对腹部照射的影响并检查各种终点。2D带状电离室阵列（SICA）检测器位于准直的上游，并用于辐照期间的体内剂量监测。在每个辐照系列之前，SICA信号与每个递送剂量率下的等中心剂量相关。剂量,剂量率,用SICA检测器监测每只小鼠的2D剂量分布。
结果：上游SICA检测器信号与等中心的输送剂量之间的校准曲线具有良好的线性，最小R2值为0.991（FLASH）和0.985（CONV），每个模态的斜率都是一致的。重新分配老鼠后，所有剂量水平的标准偏差均小于1.85%(FLASH)和0.83%(CONV)，没有个体受试者剂量落在指定剂量的±3.6%范围之外。FLASH场的场平均剂量率为79.0±0.8Gy/s，平均局部平均剂量率为160.6±3.0Gy/s。体内剂量测定允许准确检测递送剂量和计划剂量之间的变化。
结论：通过实时剂量和剂量率监测，体内剂量测定有利于FLASH实验，从而在波束波动导致递送剂量与计划剂量不同时允许小鼠队列重组。
方法：227只小鼠以FLASH或常规（CONV）剂量率用250MeV具有FLASH能力的质子束线进行照射，使用笔形束扫描表征质子FLASH对腹部照射的影响并检查各种终点。2D带状电离室阵列（SICA）检测器位于准直的上游，并用于辐照期间的体内剂量监测。在每个辐照系列之前，SICA信号与每个递送剂量率下的等中心剂量相关。剂量,剂量率,用SICA检测器监测每只小鼠的2D剂量分布。
结果：上游SICA检测器信号与等中心的输送剂量之间的校准曲线具有良好的线性，最小R2值为0.991（FLASH）和0.985（CONV），每个模态的斜率都是一致的。重新分配老鼠后，所有剂量水平的标准偏差均小于1.85%(FLASH)和0.83%(CONV)，没有个体受试者剂量落在指定剂量的±3.6%范围之外。FLASH场的场平均剂量率为79.0±0.8Gy/s，平均局部平均剂量率为160.6±3.0Gy/s。体内剂量测定允许准确检测递送剂量和计划剂量之间的变化。
结论：通过实时剂量和剂量率监测，体内剂量测定有利于FLASH实验，从而在波束波动导致递送剂量与计划剂量不同时允许小鼠队列重组。
