Laboratory of Radiation Physics, Odense University Hospital, University of Southern Denmark, DK-5000 Odense, Denmark.
Med Phys. 2011 May;38(5):2412-8. doi: 10.1118/1.3575418.
To investigate differences in calculated doses and normal tissue complication probability (NTCP) values between different dose algorithms.
Six dose algorithms from four different treatment planning systems were investigated: Eclipse AAA, Oncentra MasterPlan Collapsed Cone and Pencil Beam, Pinnacle Collapsed Cone and XiO Multigrid Superposition, and Fast Fourier Transform Convolution. Twenty NSCLC patients treated in the period 2001-2006 at the same accelerator were included and the accelerator used for treatments were modeled in the different systems. The treatment plans were recalculated with the same number of monitor units and beam arrangements across the dose algorithms. Dose volume histograms of the GTV, PTV, combined lungs (excluding the GTV), and heart were exported and evaluated. NTCP values for heart and lungs were calculated using the relative seriality model and the LKB model, respectively. Furthermore, NTCP for the lungs were calculated from two different model parameter sets. Calculations and evaluations were performed both including and excluding density corrections.
There are found statistical significant differences between the calculated dose to heart, lung, and targets across the algorithms. Mean lung dose and V20 are not very sensitive to change between the investigated dose calculation algorithms. However, the different dose levels for the PTV averaged over the patient population are varying up to 11%. The predicted NTCP values for pneumonitis vary between 0.20 and 0.24 or 0.35 and 0.48 across the investigated dose algorithms depending on the chosen model parameter set. The influence of the use of density correction in the dose calculation on the predicted NTCP values depends on the specific dose calculation algorithm and the model parameter set. For fixed values of these, the changes in NTCP can be up to 45%.
Calculated NTCP values for pneumonitis are more sensitive to the choice of algorithm than mean lung dose and V20 which are also commonly used for plan evaluation. The NTCP values for heart complication are, in this study, not very sensitive to the choice of algorithm. Dose calculations based on density corrections result in quite different NTCP values than calculations without density corrections. It is therefore important when working with NTCP planning to use NTCP parameter values based on calculations and treatments similar to those for which the NTCP is of interest.
研究不同剂量算法之间计算剂量和正常组织并发症概率（NTCP）值的差异。
研究了来自四个不同治疗计划系统的六个剂量算法：Eclipse AAA、Oncentra MasterPlan 坍塌圆锥和铅笔束、Pinnacle 坍塌圆锥和 XiO 多网格叠加以及快速傅里叶变换卷积。纳入了 2001 年至 2006 年期间在同一加速器上治疗的 20 例 NSCLC 患者，并在不同系统中对用于治疗的加速器进行了建模。使用相同数量的监测单位和光束排列在不同的剂量算法之间重新计算治疗计划。导出并评估了 GTV、PTV、合并的肺（不包括 GTV）和心脏的剂量体积直方图。使用相对序列模型和 LKB 模型分别计算心脏和肺的 NTCP 值。此外，还从两个不同的模型参数集计算了肺部的 NTCP。在包括和不包括密度校正的情况下进行了计算和评估。
发现算法之间计算的心脏、肺和靶区剂量存在统计学显著差异。平均肺剂量和 V20 对研究中的剂量计算算法之间的变化不敏感。然而，患者群体中 PTV 的平均剂量水平变化高达 11%。根据所选模型参数集，不同剂量算法之间预测的放射性肺炎 NTCP 值在 0.20 到 0.24 或 0.35 到 0.48 之间变化。在剂量计算中使用密度校正对预测 NTCP 值的影响取决于特定的剂量计算算法和模型参数集。对于这些固定值，NTCP 的变化可达 45%。
与通常用于计划评估的平均肺剂量和 V20 相比，放射性肺炎的计算 NTCP 值对算法的选择更敏感。本研究中，心脏并发症的 NTCP 值对算法的选择不敏感。基于密度校正的剂量计算会导致与不进行密度校正的计算相比，完全不同的 NTCP 值。因此，在使用 NTCP 计划时，使用与 NTCP 感兴趣的治疗和计算相似的 NTCP 参数值非常重要。
