Narayanasamy Ganesh, Saenz Daniel L, Defoor Dewayne, Papanikolaou Niko, Stathakis Sotirios
Department of Radiation Oncology, University of Texas Health San Antonio, San Antonio, TX, USA.
Department of Radiation Oncology, University of Arkansas for Medical Sciences, Little Rock, AR, USA.
J Appl Clin Med Phys. 2017 Nov;18(6):123-129. doi: 10.1002/acm2.12188. Epub 2017 Sep 25.
The purpose of this study is to perform dosimetric validation of Monaco treatment planning system version 5.1. The Elekta VersaHD linear accelerator with high dose rate flattening filter-free photon modes and electron energies was used in this study. The dosimetric output of the new Agility head combined with the FFF photon modes warranted this investigation into the dosimetric accuracy prior to clinical usage. A model of the VersaHD linac was created in Monaco TPS by Elekta using commissioned beam data including percent depth dose curves, beam profiles, and output factors. A variety of 3D conformal fields were created in Monaco TPS on a combined Plastic water/Styrofoam phantom and validated against measurements with a calibrated ion chamber. Some of the parameters varied including source to surface distance, field size, wedges, gantry angle, and depth for all photon and electron energies. In addition, a series of step and shoot IMRT, VMAT test plans, and patient plans on various anatomical sites were verified against measurements on a Delta diode array. The agreement in point dose measurements was within 2% for all photon and electron energies in the homogeneous phantom and within 3% for photon energies in the heterogeneous phantom. The mean ± SD gamma passing rates of IMRT test fields yielded 93.8 ± 4.7% based on 2% dose difference and 2 mm distance-to-agreement criteria. Eight previously treated IMRT patient plans were replanned in Monaco TPS and five measurements on each yielded an average gamma passing rate of 95% with 6.7% confidence limit based on 3%, 3 mm gamma criteria. This investigation on dosimetric validation ensures accuracy of modeling VersaHD linac in Monaco TPS thereby improving patient safety.
本研究的目的是对Monaco治疗计划系统5.1版本进行剂量学验证。本研究使用了配备高剂量率无均整器光子模式和电子能量的医科达VersaHD直线加速器。新型Agility机头与FFF光子模式的剂量学输出，使得在临床使用前对剂量学准确性进行此项研究成为必要。医科达利用包括百分深度剂量曲线、射野轮廓和输出因子在内的已调试射束数据，在Monaco治疗计划系统中创建了VersaHD直线加速器的模型。在Monaco治疗计划系统中，在塑料水/聚苯乙烯泡沫组合体模上创建了各种三维适形野，并用校准后的电离室测量结果进行验证。对所有光子和电子能量，改变了一些参数，包括源皮距、射野大小、楔形板、机架角度和深度。此外，针对Delta二极管阵列的测量结果，对一系列静态调强放疗、容积调强弧形放疗测试计划以及不同解剖部位的患者计划进行了验证。在均匀体模中，所有光子和电子能量的点剂量测量一致性在2%以内，在非均匀体模中，光子能量的点剂量测量一致性在3%以内。基于2%剂量差异和2毫米距离一致性标准，调强放疗测试野的平均±标准差γ通过率为93.8±4.7%。在Monaco治疗计划系统中对8个先前治疗过的调强放疗患者计划重新进行了规划，每个计划进行5次测量，基于3%、3毫米γ标准，平均γ通过率为95%，置信限为6.7%。这项剂量学验证研究确保了在Monaco治疗计划系统中对VersaHD直线加速器建模的准确性，从而提高了患者安全性。
