University Hospital Wurzburg, Department of Radiation Oncology, Wuerzburg, Germany.
Ernst-Abbe-Hochschule Jena, Jena, Germany.
J Appl Clin Med Phys. 2023 Dec;24(12):e14139. doi: 10.1002/acm2.14139. Epub 2023 Sep 10.
Secondary dose calculation (SDC) with an independent algorithm is one option to perform plan-specific quality assurance (QA). While measurement-based QA can potentially detect errors in plan delivery, the dose values are typically only compared to calculations on homogeneous phantom geometries instead of patient CT data. We analyzed the sensitivity and specificity of an SDC software by purposely introducing different errors and determined thresholds for optimal decisions.
Thirty head and neck VMAT plans and 30 modifications of those plans, including errors related to density and beam modelling, were recalculated using RadCalc with a Monte Carlo algorithm. Decision thresholds were obtained by receiver operating characteristics (ROC) analysis. For comparison, measurement-based QA using the ArcCHECK phantom was carried out and evaluated in the same way.
Despite optimized decision thresholds, none of the systems was able to reliably detect all errors. ArcCHECK analysis using a 2%/2 mm criterion with a threshold of 91.1% had an area under the curve (AUC) of 0.80. Evaluating differences in recalculated and planned DVH parameter of the target structures in RadCalc with a 2% threshold an AUC of 0.86 was achieved. Out-of-field deviations could be attributed to weaknesses in the beam model.
Secondary dose calculation with RadCalc is an alternative to established measurement-based phantom QA. Different tools catch different errors; therefore, a combination of approaches should be preferred.
使用独立算法进行二次剂量计算（SDC）是执行特定计划质量保证（QA）的一种选择。虽然基于测量的 QA 有可能检测到计划交付中的错误，但剂量值通常仅与同质体模几何形状上的计算进行比较，而不是与患者 CT 数据进行比较。我们通过有意引入不同的误差来分析 SDC 软件的灵敏度和特异性，并确定最佳决策的阈值。
使用 RadCalc 及其蒙特卡罗算法重新计算了 30 个头颈部 VMAT 计划和 30 个这些计划的修改，包括与密度和射束建模相关的误差。通过接收者操作特征（ROC）分析获得决策阈值。为了进行比较，使用 ArcCHECK 体模进行了基于测量的 QA，并以相同的方式进行了评估。
尽管优化了决策阈值，但没有一个系统能够可靠地检测到所有的误差。使用 2%/2mm 标准和 91.1%的阈值的 ArcCHECK 分析的曲线下面积（AUC）为 0.80。在 RadCalc 中，使用 2%的阈值评估目标结构的计划和重新计算的剂量体积直方图（DVH）参数之间的差异，AUC 为 0.86。场外偏差可归因于射束模型的弱点。
使用 RadCalc 进行二次剂量计算是对既定基于测量的体模 QA 的替代方法。不同的工具可以捕捉到不同的误差；因此，应优先采用组合方法。
