Geometrical source modeling of 6MV flattening-filter-free (FFF) beam from TrueBeam linear accelerator and its commissioning validation using Monte Carlo simulation approach for radiotherapy,Radiation Physics and Chemistry

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Geometrical source modeling of 6MV flattening-filter-free (FFF) beam from TrueBeam linear accelerator and its commissioning validation using Monte Carlo simulation approach for radiotherapy
Radiation Physics and Chemistry ( IF 2.8 ) Pub Date : 2022-06-24 , DOI: 10.1016/j.radphyschem.2022.110339
Ravindra Shende , S.J. Dhoble , Gourav Gupta

Purpose

To study geometrical source modeling of 6 MV flattening-filter-free (FFF) beam from TrueBeam linear accelerator and its commissioning validation using Monte Carlo simulation approach.

Methods & material

Source modeling of 6MVFFF beam from TrueBeam linear accelerator has been accomplished by using PRIMO as the Monte-Carlo (MC) simulation software based on PENELOPE code. Initially, source modeling of 6MVFFF beam was validated against experimentally measured Percentage-depth-dose (PDD) and profile for 10 × 10cm² field. Followed by commissioning validation of 6MVFFF beam has been carried out by simulating PDDs, profiles and output factors for range of field sizes. Besides, verification of absolute dose, beam quality index, performance analysis of dose distribution in heterogeneous phantom and simulation of radiation treatment plan for validation of Treatment planning system (TPS) was performed. Simulated results compared against measured; dose distributions were analyzed using gamma analysis with acceptance criteria of 2% Dose-difference (DD) and 2 mm Distance-to-agreement (DTA).

Results

Gamma analysis for all the simulated and measured PDDs and profiles shows minimum passing rate of 100% and 98.04% respectively. Simulated values of absolute point dose, beam quality index and output factors shows good agreements with measurements. Gamma analysis of depth dose distribution in heterogeneous phantom obtained using MC simulation and calculated with Analytical anisotropic algorithm (AAA) agreed within 95.89%. However, heterogeneous medium of very high and low-density region shows larger dose discrepancy between MC and AAA due to the poor modeling of AAA compared to MC. The percentage of 99.81% of gamma passing and comparison of predicted Dose-volume-histogram (DVH) shows good resemblance between PRIMO simulated and AAA calculated plan.

Conclusion

Study concludes that PRIMO is an independent MC simulation tools for verification and commissioning validation of external beam radiotherapy in treatment of cancer. The MC validation of external beam therapy modules grants higher confidence in accuracy of radiation dose delivery.

中文翻译：

来自 TrueBeam 直线加速器的 6MV 无扁平滤波器 (FFF) 光束的几何源建模及其使用蒙特卡罗模拟方法进行放射治疗的调试验证

目的

研究 TrueBeam 直线加速器的 6 MV 无扁平滤波器 (FFF) 光束的几何源建模及其使用蒙特卡罗模拟方法的调试验证。

方法和材料

TrueBeam 直线加速器的 6MVFFF 光束的源建模是通过使用 PRIMO 作为基于 PENELOPE 代码的 Monte-Carlo (MC) 仿真软件完成的。最初，针对 10 × 10cm ^{2的实验测量百分比深度剂量 (PDD) 和剖面验证了 6MVFFF 光束的源建模}场地。随后，通过模拟 PDD、剖面和输出因子的范围，对 6MVFFF 光束进行了调试验证。此外，还进行了绝对剂量、光束质量指标的验证、异质体模中剂量分布的性能分析以及放射治疗计划的模拟，以验证治疗计划系统（TPS）。模拟结果与测量结果比较；使用伽马分析分析剂量分布，接受标准为 2% 剂量差 (DD) 和 2 毫米协议距离 (DTA)。

结果

所有模拟和测量的 PDD 和配置文件的 Gamma 分析显示最低通过率分别为 100% 和 98.04%。绝对点剂量、光束质量指数和输出因子的模拟值显示与测量值的良好一致性。使用 MC 模拟获得的异质体模中深度剂量分布的伽马分析，并使用分析各向异性算法 (AAA) 进行计算，同意率在 95.89% 以内。然而，由于与 MC 相比，AAA 的建模较差，非常高和低密度区域的异质介质在 MC 和 AAA 之间显示出更大的剂量差异。99.81% 的伽马通过百分比和预测剂量-体积-直方图 (DVH) 的比较表明 PRIMO 模拟和 AAA 计算计划之间有很好的相似性。