Aim

In this study, an EGSnrc based Monte Carlo electron model was validated for an Elekta Synergy® 160-leaf Agility™ linear accelerator. A previously reported electron energy straggling model based on a Lévy distribution was tested against water tank measurements and a specially designed heterogeneous multi-layered phantom. This included PDD, beam profile, and relative output factor (ROF) comparison. All data passed a 2%/2 mm gamma criterion with the exception of some ROF data, which showed discrepancies of up to 2.7%.

Methods

BEAMnrc was used to accurately model the linac that included the improved exit electron energy spectrum based on a Lévy distribution. The resulting BEAMnrc phase space files were used as sources in DOSXYZnrc for water tank dose distribution simulations consisting of 6 electron beam energies, 11 field sizes, and source-to-surface distances (SSDs) of 95 and 100 cm. Evaluation parameters included PDD, dose profiles, and relative output factors, as well as phantom PDD and dose profile measurements with EBT3 gafchromic film.

Results

The improved exit electron beam energy spectrum caused simulated data to comply with measured data (PPD's and dose profiles) with a 100% pass rate using a 2%/2 mm criterion except for some relative output factors that deviated by 2.7% from measured ones in water. This was observed for both 95 and 100 cm SSD data. Good agreement was obtained between film and simulation data within 2% in more than 90% of PDD and profile measurements.

Conclusions

The Lévy based energy straggling model for electron beams allowed for accurate electron beam characterization in water tank and phantom measurements.

中文翻译：

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ElektaSynergy®线性加速器的Lévy电子能量散布模型的验证。

目标

在这项研究中，针对ElektaSynergy®160叶Agility™线性加速器验证了基于EGSnrc的蒙特卡洛电子模型。针对水箱测量和专门设计的异质多层体模，测试了先前报告的基于Lévy分布的电子能量散布模型。其中包括PDD，光束轮廓和相对输出因子（ROF）比较。除某些ROF数据外，所有数据均通过了2％/ 2 mm的伽玛标准，该数据显示差异高达2.7％。

方法

BEAMnrc用于基于Lévy分布对包括改进的出射电子能谱的直线加速器进行精确建模。所得的BEAMnrc相空间文件用作DOSXYZnrc中的水源，用于水箱剂量分布模拟，包括6个电子束能量，11个场大小以及95和100 cm的源到表面距离（SSD）。评估参数包括PDD，剂量分布和相对输出因子，以及幻影PDD和使用EBT3变色薄膜的剂量分布测量。

结果

改进的出射电子束能谱使模拟数据与测量数据（PPD和剂量曲线）相符，使用2％/ 2 mm的标准具有100％的通过率，但某些相对输出因子与实测数据相比偏离了2.7％。水。对于95和100 cm SSD数据都可以观察到。在超过90％的PDD和轮廓测量中，胶片和模拟数据之间的吻合度在2％以内。

结论

基于Lévy的电子束能量散布模型可以在水箱和体模测量中准确表征电子束。