多种三维剂量验证系统在肺癌VMAT剂量验证中的联合应用

目的 联合应用两种商用及一种自行开发的基于加速器轨迹日志(LFB)的三维剂量重建系统验证肺癌VMAT计划。方法 编程实现读取TrueBeam轨迹日志中误差并导入计划系统生成重建剂量。选18例肺癌双弧VMAT计划,用ArcCheck测量并利用3DVH重建,同时使用LFB和Compass计算模式重建。其中5例4h内由ArcCheck测2次,检测加速器重复性。将18例计划移植到建成5cm、背散4cm、中心放置有FC65-G电离室的固体水模上计算电离室平均剂量并与实测及3种重建系统重建点剂量比对。结果 加速器重复性稳定。LFB、3DVH、Compass及FC-65G实测与计划点剂量偏差≤2%。ArcCheck曲面二维,3DVH、Compass整体及LBF所有器官三维γ通过率在所有比对标准下均>90%,3DVH及Compass个别器官γ通过率低。重建剂量与原计划相比,LBF差异最小,除肺之外器官Compass差异居中、3DVH最大。结论 LBF、3DVH、Compass 3种系统能从不同方面反映肺癌VMAT剂量验证结果,联合应用三者进行剂量验证能更直观的展现出验证结果,便于后续分析。

Evaluation the combined effect of three dose reconstruction systems on VMAT dosimetry verification of lung cancer

Objective To evaluate the combined effect of an trajectory log field based(LBF)and two commercial dose reconstruction systems on volume-modulated arc therapy(VMAT)dose verification of lung cancer. Methods An in-house program was developed to introduce errors in trajectory log of TrueBeam to the origin plan and recalculate the dose of the error plan in treatment planning system(TPS). A total of 18 lung cancer cases treated by two-arc VMAT were selected to perform on LINAC and measured by ArcCheck simultaneously. Then, the reconstructed doses were obtained by 3DVH. The mode of reconstruction was calculated by LFB and Compass. Five of the 18 cases were performed on LINAC two times in four hours and measured by ArcCheck to evaluate the stability of the TrueBeam performance. The 18 plans were recalculated and performed on LINAC with a solid water phantom with 5 cm build-up, 4 cm back scattering thickness and a FC65-G detector in the center. The measured dose by detector was compared with the reconstructed dose by three systems. Results TheTruebeam performance was stable. For all of the 18 cases, the point dose measured by FC65-G and reconstructed by three systems had a deviation of less than 2% to the TPS calculated. For all of the organs reconstructed by LBF and most organs reconstructed by 3DVH and Compass, the γ pass rate between them and TPS all exceeded 90% under all criteria, as well as the ArcCheck measured Results. For all the organ dose difference between reconstructed and TPS, LBF system had the smallest difference, followed by the Compass system except the lung, and the 3DVH had the highest difference. Conclusions LBF, 3DVH and Compass can reflect the VMAT dose verification Results of lung cancer from different perspectives. The combined application of three systems can demonstrate the verification Results in an intuitive manner, which is beneficial for subsequent analysis.