背景:超高剂量率(UHDR)电子束已普遍用于FLASH研究以及将FLASH放射疗法(RT)转化为临床。EDGE二极管检测器具有用于UHDR剂量测定的潜在用途,尽管观察到射束能量依赖性。
目的:目的是根据束能量呈现EDGE探测器的电子束响应,为了表征EDGE检测器在UHDR条件下的响应,并根据测量结果验证从EDGE二极管的第一个详细蒙特卡罗模型得出的校正因子,特别是在UHDR条件下。
方法:用EDGE检测器和胶片测量UHDRMobetron的百分比深度剂量(PDD)。已根据制造商根据NDA协议提供的蓝图配置了EDGE检测器的详细蒙特卡罗(MC)模型。已计算出EDGE检测器对一系列单能电子束的水/硅剂量比。还研究了FLASH相关电子束的水/硅剂量比对深度的依赖性。建立了用EDGE检测器校正PDD的分析方法。
结果:水/硅剂量比随着电子束能量的降低而降低。对于Mobetron9MeVUHDR电子束,在积聚区域,该比率从1.09下降到1.03,在下降区域保持在0.98-1.02的范围内,并在尾部上升到1.08的平台值。通过应用更正,通过EDGE检测器测量的PDD与用胶片测量的PDD之间实现了良好的一致性。
结论:具有UHDR能力的EDGE检测器的电子束响应从利用复杂的MC模型的第一原理导出。对UHDR电子束的PDD进行了分析方法的验证。结果证明了EDGE检测器在测量UHDR电子束的PDD中的能力。
BACKGROUND: Ultra-high-dose-rate (UHDR) electron beams have been commonly utilized in FLASH studies and the translation of FLASH Radiotherapy (RT) to the clinic. The EDGE diode detector has potential use for UHDR dosimetry albeit with a beam energy dependency observed.
OBJECTIVE: The purpose is to present the electron beam response for an EDGE detector in dependence on beam energy, to characterize the EDGE detector\'s response under UHDR conditions, and to validate correction factors derived from the first detailed Monte Carlo model of the EDGE diode against measurements, particularly under UHDR conditions.
METHODS: Percentage depth doses (PDDs) for the UHDR Mobetron were measured with both EDGE detectors and films. A detailed Monte Carlo (MC) model of the EDGE detector has been configured according to the blueprint provided by the manufacturer under an NDA agreement. Water/silicon dose ratios of EDGE detector for a series of mono-energetic electron beams have been calculated. The dependence of the water/silicon dose ratio on depth for a FLASH relevant electron beam was also studied. An analytical approach for the correction of PDD measured with EDGE detectors was established.
RESULTS: Water/silicon dose ratio decreased with decreasing electron beam energy. For the Mobetron 9 MeV UHDR electron beam, the ratio decreased from 1.09 to 1.03 in the build-up region, maintained in range of 0.98-1.02 at the fall-off region and raised to a plateau in value of 1.08 at the tail. By applying the corrections, good agreement between the PDDs measured by the EDGE detector and those measured with film was achieved.
CONCLUSIONS: Electron beam response of an UHDR capable EDGE detector was derived from first principles utilizing a sophisticated MC model. An analytical approach was validated for the PDDs of UHDR electron beams. The results demonstrated the capability of EDGE detector in measuring PDDs of UHDR electron beams.