单层多叶准直器和双层堆叠多叶准直器治疗计划中治疗计划系统参数对射束调制复杂性的影响。
Effect of treatment planning system parameters on beam modulation complexity for treatment plans with single-layer multi-leaf collimator and dual-layer stacked multi-leaf collimator.
机构信息
Medical Physics Service, Castle Hill Hospital, Hull University Teaching Hospitals NHS Trust, Hull, UK.
Department of Physics and Mathematics, University of Hull, Hull, UK.
出版信息
Br J Radiol. 2021 Jun 1;94(1122):20201011. doi: 10.1259/bjr.20201011. Epub 2021 Apr 29.
OBJECTIVE
High levels of beam modulation complexity (MC) and monitor units (MU) can compromise the plan deliverability of intensity-modulated radiotherapy treatments. Our study evaluates the effect of three treatment planning system (TPS) parameters on MC and MU using different multi-leaf collimator (MLC) architectures.
METHODS
192 volumetric modulated arc therapy plans were calculated using one virtual prostate phantom considering three main settings: (1) three TPS-parameters (Convergence; Aperture Shape Controller, ASC; and Dose Calculation Resolution, DCR) selected from Eclipse v15.6, (2) four levels of dose-sparing priority for organs at risk (OAR), and (3) two treatment units with same nominal conformity resolution and different MLC architectures (Halcyon-v2 dual-layer MLC, DL-MLC & TrueBeam single-layer MLC, SL-MLC). We use seven complexity metrics to evaluate the MC, including two new metrics for DL-MLC, assessed by their correlation with γ passing rate (GPR) analysis.
RESULTS
DL-MLC plans demonstrated lower dose-sparing values than SL-MLC plans (<0.05). TPS-parameters did not change significantly the complexity metrics for either MLC architectures. However, for SL-MLC, significant variations of MU, target volume dose-homogeneity, and dose spillage were associated with ASC and DCR (<0.05). MU were found to be correlated (highly or moderately) with all complexity metrics (<0.05) for both MLC plans. Additionally, our new complexity metrics presented a moderate correlation with GPR (<0.65). An important correlation was demonstrated between MC (plan deliverability) and dose-sparing priority level for DL-MLC.
CONCLUSIONS
TPS-parameters selected do not change MC for DL-MLC architecture, but they might have a potential use to control the MU, PTV homogeneity or dose spillage for SL-MLC. Our new DL-MLC complexity metrics presented important information to be considered in future pre-treatment quality assurance programs. Finally, the prominent dependence between plan deliverability and priority applied to OAR dose sparing for DL-MLC needs to be analyzed and considered as an additional predictor of GPRs in further studies.
ADVANCES IN KNOWLEDGE
Dose-sparing priority might influence in modulation complexity of DL-MLC.
目的
高的射束调制复杂度（MC）和监视器单位（MU）可能会影响调强放疗计划的实施。本研究使用不同的多叶准直器（MLC）结构评估三个治疗计划系统（TPS）参数对 MC 和 MU 的影响。
方法
使用一个虚拟前列腺体模计算了 192 个容积调强弧形治疗计划，考虑了三个主要设置：（1）从 Eclipse v15.6 中选择的三个 TPS 参数（收敛；孔径形状控制器，ASC；和剂量计算分辨率，DCR），（2）危及器官（OAR）的四个剂量节省优先级，以及（3）两个具有相同名义适形分辨率但 MLC 结构不同的治疗单元（Halcyon-v2 双层 MLC，DL-MLC 和 TrueBeam 单层 MLC，SL-MLC）。我们使用七个复杂性指标来评估 MC，包括两个新的用于评估 DL-MLC 的指标，通过它们与 γ通过率（GPR）分析的相关性进行评估。
结果
与 SL-MLC 计划相比，DL-MLC 计划的剂量节省值较低（<0.05）。对于这两种 MLC 结构，TPS 参数并没有显著改变复杂性指标。然而，对于 SL-MLC，ASC 和 DCR 与 MU、靶区剂量均匀性和剂量泄漏显著相关（<0.05）。MU 与两种 MLC 计划的所有复杂性指标均呈高度或中度相关（<0.05）。此外，我们的新复杂性指标与 GPR 呈中度相关（<0.65）。对于 DL-MLC，MC（计划可实施性）与剂量节省优先级水平之间存在重要的相关性。
结论
对于 DL-MLC 结构，选择的 TPS 参数不会改变 MC，但它们可能有助于控制 MU、PTV 均匀性或 SL-MLC 的剂量泄漏。我们的新的 DL-MLC 复杂性指标提供了重要的信息，可在未来的治疗前质量保证计划中加以考虑。最后，DL-MLC 中 OAR 剂量节省优先级与计划可实施性之间的显著相关性需要进一步分析，并作为 GPR 的附加预测因子在进一步的研究中进行考虑。
知识进展
剂量节省优先级可能会影响 DL-MLC 的调制复杂度。
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