Stathakis Sotirios, Narayanasamy Ganesh, Licon Anna Laura, Myers Pamela, Li Ying, Crownover Richard, Papanikolaou Niko
Department of Radiation Oncology, Mays Cancer Center, University of Texas Health San Antonio, TX 78229, USA.
J BUON. 2019 Mar-Apr;24(2):838-843.
The purpose of this study was to investigate the dosimetric equivalency of dynamic conformal arc therapy (DCAT) against volumetric modulated arc therapy (VMAT) plans in stereotactic body radiation therapy (SBRT) of lung and liver lesions and to examine if efficiency can be increased.
Nineteen patients previously treated for lung and liver cancer lesions with SBRT were included. Organs at risk (OAR) and targets were contoured by a single radiation oncologist. All plans were optimized by the same dosimetrist using ELEKTA Monaco treatment planning system version 5.0 for 6MV flattening filter free (FFF) photon beam in a VersaHD (ELEKTA, Crawley, UK). A VMAT and DCAT plan was optimized using the same objectives using coplanar arcs of 225o arc span.
All plans have achieved the target and OAR planning objectives. The target dose conformity was comparable (mean VMAT PTVr=1.3 and DCAT PTVr=1.4), and the low dose spillage were similar (mean VMAT R50=4.5 and DCAT R50=4.6). However, monitor units (MU) for DCAT plans were lower by 2.5 times on average than VMAT plans. It was observed that in 75% of cases where OARs overlapped with the PTV, maximum doses to OAR were higher in VMAT than DCAT plans, but the difference was not significant. Patient specific quality assurance (QA) plans were measured using the Scandidos Delta4 phantom and gamma analysis performed using 2mm distance to agreement (DTA) and 2% dose difference yielded more than 95% passing rates on both VMAT and DCAT plans.
DCAT delivery for lung and liver SBRT is a dosimetrically equivalent and an efficient alternative to VMAT plans.
本研究旨在探讨在肺部和肝脏病变的立体定向体部放射治疗（SBRT）中，动态适形弧形调强放疗（DCAT）与容积调强弧形放疗（VMAT）计划的剂量等效性，并研究是否能提高效率。
纳入19例先前接受过肺部和肝脏癌症病变SBRT治疗的患者。由一名放射肿瘤学家勾勒出危及器官（OAR）和靶区。所有计划均由同一名剂量师使用医科达Monaco治疗计划系统5.0版本，针对VersaHD（医科达，英国克劳利）中的6MV无均整器（FFF）光子束进行优化。使用相同目标，通过225°弧跨度的共面弧形对VMAT和DCAT计划进行优化。
所有计划均达到了靶区和OAR的计划目标。靶区剂量适形性相当（平均VMAT计划的PTVr = 1.3，DCAT计划的PTVr = 1.4），低剂量溢出情况相似（平均VMAT计划的R50 = 4.5，DCAT计划的R50 = 4.6）。然而，DCAT计划的监测单位（MU）平均比VMAT计划低2.5倍。观察到在75%的OAR与PTV重叠的病例中，VMAT计划中OAR的最大剂量高于DCAT计划，但差异不显著。使用Scandidos Delta4体模测量患者特定质量保证（QA）计划，并使用2mm的距离一致性（DTA）和2%的剂量差异进行伽马分析，VMAT和DCAT计划的通过率均超过95%。
肺部和肝脏SBRT的DCAT技术在剂量学上与VMAT计划等效，且是一种有效的替代方案。
