PDF(Pubmed)
Abstract：
Purpose We sought to explore the feasibility of using the current co-planar Halcyon ring delivery system (RDS) with a novel multileaf collimator (MLC) aperture shape controller in delivering a single high dose of 30 Gy to solitary lung lesions via stereotactic body radiotherapy (SBRT). Materials and methods Thirteen non-small-cell lung cancer (NSCLC) patients previously treated with a single dose of 30 Gy to lung lesions via SBRT on the TrueBeam (6MV-FFF) using non-coplanar volumetric modulated arc therapy (VMAT) arcs were anonymized and replanned onto the Halcyon RDS (6MV-FFF) following RTOG-0915 single-fraction criteria. The Halcyon plans utilized a novel dynamic conformal arc (DCA)-based MLC-fitting approach before VMAT optimization with a user-defined aperture shape controller option. The clinical TrueBeam and Halcyon plans were compared via their protocol compliance, target conformity, gradient index, and dose to organs-at-risk (OAR). Treatment delivery efficacy and accuracy were assessed through end-to-end quality assurance (QA) tests on Halcyon and independent dose verification via in-house Monte Carlo (MC) second-check validation. Results All Halcyon lung SBRT plans met RTOG-0915 protocol\'s requirements for target coverage, conformity, and gradient indices, and maximum dose 2 cm away from the target (D2cm) while being statistically insignificant (p > 0.05) when compared to clinical TrueBeam plans. Additionally, Halcyon provided a similar dose to OAR except for the ribs, where Halcyon demonstrated a lower maximum dose (15.22 Gy vs 17.01 Gy, p < 0.001). However, Halcyon plans required a higher total monitor unit (8892 MU vs 7413 MU, p < 0.001), resulting in a higher beam modulation factor (2.96 MU/cGy vs 2.47 MU/cGy, p < 0.001) and an increase in beam-on time by a factor of 2.1 (11.11 min vs 5.3 min, p < 0.005). End-to-end QA measurements demonstrate that Halcyon plans were clinically acceptable with an average gamma passing rate of 99.8% for 2%/2mm criteria and independent MC 2nd checks within ±2.86%. Conclusion Our end-to-end testing and validation study demonstrates that by utilizing a DCA-based MLC aperture shape controller before VMAT optimization, Halcyon can be used for delivering a single dose of lung SBRT treatment. However, future improvements of Halcyon RDS are recommended to allow higher output rates, rotational couch corrections, and an integrated intrafraction motion management system that will further enhance Halcyon\'s capability for site-specific single dosage of SBRT.
摘要：
目的我们试图探索使用当前的共平面Halcyon环递送系统（RDS）与新型多叶准直器（MLC）孔径形状控制器通过立体定向放射治疗（SBRT）将30Gy的单次高剂量递送到孤立性肺病变的可行性。材料和方法先前使用非共面体积调节电弧疗法（VMAT）弧在TrueBeam（6MV-FFF）上通过SBRT对肺部病变进行了30Gy单剂量治疗的13名非小细胞肺癌（NSCLC）患者匿名化并按照RTOG-0915单分数标准重新扫描到HalcyonRDS（6MV-FFF）上。Halcyon计划在使用用户定义的孔径形状控制器选项进行VMAT优化之前，利用了一种新颖的基于动态共形弧（DCA）的MLC拟合方法。临床TrueBeam和Halcyon计划通过其协议合规性进行比较，目标一致性,梯度指数,和对危险器官(OAR)的剂量。通过Halcyon的端到端质量保证（QA）测试和通过内部蒙特卡洛（MC）第二次检查验证的独立剂量验证来评估治疗交付的有效性和准确性。结果所有Halcyon肺SBRT计划均符合RTOG-0915协议对目标覆盖的要求，一致性,和梯度指数，和最大剂量2cm远离目标(D2cm),而在与临床TrueBeam计划相比时统计学上不显著(p>0.05)。此外,Halcyon提供了与OAR相似的剂量，除了肋骨，Halcyon的最大剂量较低（15.22Gyvs17.01Gy，p<0.001)。然而,Halcyon计划需要更高的总监控单元(8892MUvs7413MU,p<0.001)，导致更高的波束调制因子(2.96MU/cGyvs2.47MU/cGy，p<0.001），并且开束时间增加了2.1倍（11.11分钟vs5.3分钟，p<0.005)。端到端QA测量表明Halcyon计划在临床上是可接受的，2％/2mm标准的平均伽马通过率为99.8％，独立的MC第二次检查在±2.86％之内。结论我们的端到端测试和验证研究表明，通过在VMAT优化之前利用基于DCA的MLC孔径形状控制器，Halcyon可用于递送单剂量的肺SBRT治疗。然而,HalcyonRDS的未来改进建议允许更高的输出率，旋转沙发校正，和一个集成的帧内运动管理系统，将进一步增强Halcyon对特定地点单剂量SBRT的能力。
