CREATIS, CNRS UMR5220, Inserm U1044, INSA-Lyon, Université Lyon 1, Lyon, France.
Phys Med Biol. 2012 Jul 7;57(13):4223-44. doi: 10.1088/0031-9155/57/13/4223. Epub 2012 Jun 8.
Active scanning delivery systems take full advantage of ion beams to best conform to the tumor and to spare surrounding healthy tissues; however, it is also a challenging technique for quality assurance. In this perspective, we upgraded the GATE/GEANT4 Monte Carlo platform in order to recalculate the treatment planning system (TPS) dose distributions for active scanning systems. A method that allows evaluating the TPS dose distributions with the GATE Monte Carlo platform has been developed and applied to the XiO TPS (Elekta), for the IBA proton pencil beam scanning (PBS) system. First, we evaluated the specificities of each dose engine. A dose-conversion scheme that allows one to convert dose to medium into dose to water was implemented within GATE. Specific test cases in homogeneous and heterogeneous configurations allowed for the estimation of the differences between the beam models implemented in XiO and GATE. Finally, dose distributions of a prostate treatment plan were compared. In homogeneous media, a satisfactory agreement was generally obtained between XiO and GATE. The maximum stopping power difference of 3% occurred in a human tissue of 0.9 g cm(-3) density and led to a significant range shift. Comparisons in heterogeneous configurations pointed out the limits of the TPS dose calculation accuracy and the superiority of Monte Carlo simulations. The necessity of computing dose to water in our Monte Carlo code for comparisons with TPSs is also presented. Finally, the new capabilities of the platform are applied to a prostate treatment plan and dose differences between both dose engines are analyzed in detail. This work presents a generic method to compare TPS dose distributions with the GATE Monte Carlo platform. It is noteworthy that GATE is also a convenient tool for imaging applications, therefore opening new research possibilities for the PBS modality.
主动扫描递送系统充分利用离子束来最佳地适应肿瘤并保护周围的健康组织；然而，这也是质量保证的一项具有挑战性的技术。在这种情况下，我们升级了 GATE/GEANT4 蒙特卡罗平台，以便重新计算主动扫描系统的治疗计划系统 (TPS) 剂量分布。已经开发了一种允许使用 GATE 蒙特卡罗平台评估 TPS 剂量分布的方法，并将其应用于 Elekta 的 XiO TPS 和 IBA 质子铅笔束扫描 (PBS) 系统。首先，我们评估了每个剂量引擎的特点。在 GATE 中实现了一种允许将介质中的剂量转换为水中剂量的剂量转换方案。在均匀和非均匀配置中的特定测试案例允许估计在 XiO 和 GATE 中实现的束模型之间的差异。最后，比较了前列腺治疗计划的剂量分布。在均匀介质中，XiO 和 GATE 之间通常可以获得令人满意的一致性。最大停止功率差异为 3%，发生在密度为 0.9 g cm(-3) 的人体组织中，导致明显的射程偏移。在非均匀配置中的比较指出了 TPS 剂量计算精度的局限性和蒙特卡罗模拟的优越性。还介绍了在我们的蒙特卡罗代码中计算水剂量以与 TPS 进行比较的必要性。最后，该平台的新功能应用于前列腺治疗计划，并详细分析了两种剂量引擎之间的剂量差异。这项工作提出了一种将 TPS 剂量分布与 GATE 蒙特卡罗平台进行比较的通用方法。值得注意的是，GATE 也是成像应用的便捷工具，因此为 PBS 模式开辟了新的研究可能性。
