Key laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Radiation Oncology, Peking University Cancer Hospital & Institute, Beijing, China.
Key laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Radiation Oncology, Peking University Cancer Hospital & Institute, Beijing, China.
Phys Med. 2020 Mar;71:14-23. doi: 10.1016/j.ejmp.2020.01.023. Epub 2020 Feb 19.
The aim of this study is to compare the dosimetric and mechanical accuracy of Volumetric Modulation Arc Therapy (VMAT) delivery on the Halcyon, a recent ring-shaped Treatment Delivery System (TDS) featuring fast rotating gantry, with a conventional C-arm Linac.
The comparison was performed via log file analysis, where mechanical parameters of related components was extracted. 480 and 3951 VMAT log files of clinically delivered fractions from a Halcyon and a TrueBeam Linac were analyzed respectively. The relations between mechanical parameters and errors were extensively explored to further investigate the differences between the two Linacs. The mechanical parameter fluctuations were taken into account for dose recalculations, and the Dose Volume Parameters (DVP) on the PTV were evaluated to quantify such dosimetric variations.
The Multi-Leaf Collimator (MLC) leaf mean Root Mean Square (RMS) errors were 0.028 mm and 0.031 mm for Halcyon and TrueBeam respectively. Maximum systematic error on the MLC leaves introduced by the gravity effect were 0.04 mm and 0.01 mm for the Halcyon and TrueBeam respectively. Thanks to the O-ring design, the Halcyon achieved 0.035° in mean RMS error in gantry angle compared with the 0.065° of the TrueBeam. Overall mechanical errors introduced similar levels of dose-volume parameter variations (about 0.1%) on both Linacs.
The Halcyon TDS can achieve similar mechanical leaf positioning accuracy compared with the TrueBeam TDS with a doubled delivery speed. In terms of dosimetric accuracy, The DVP standard deviations on the studied TB are generally larger than that on the Halcyon.
本研究旨在比较最近推出的具有快速旋转机架的环形治疗输送系统（TDS）—— Halcyon 与传统 C 臂直线加速器在容积调强弧形治疗（VMAT）输送中的剂量学和机械精度。
通过日志文件分析进行比较，提取相关组件的机械参数。分别分析 Halcyon 和 TrueBeam 直线加速器临床输送的 480 个和 3951 个 VMAT 日志文件。广泛探讨机械参数与误差之间的关系，以进一步研究两种直线加速器之间的差异。考虑机械参数波动进行剂量重算，并评估 PTV 的剂量体积参数（DVP），以量化这种剂量学变化。
多叶准直器（MLC）叶片平均均方根（RMS）误差分别为 Halcyon 为 0.028mm 和 TrueBeam 为 0.031mm。重力效应引起的 MLC 叶片最大系统误差分别为 Halcyon 为 0.04mm 和 TrueBeam 为 0.01mm。由于 O 型环设计，Halcyon 的机架角度 RMS 误差平均值为 0.035°，而 TrueBeam 为 0.065°。总体而言，两种直线加速器的机械误差都导致了类似水平的剂量体积参数变化（约 0.1%）。
Halcyon TDS 可以实现与具有双倍输送速度的 TrueBeam TDS 相似的机械叶片定位精度。在剂量学精度方面，研究中的 TB 的 DVP 标准偏差通常大于 Halcyon 的标准偏差。
