Keeling Vance, Algan Ozer, Ahmad Salahuddin, Hossain Sabbir
Department of Radiation Oncology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73013, USA.
J Radiosurg SBRT. 2016;4(3):235-243.
We compared treatment plan quality based on target coverage and normal brain tissue sparing for two intracranial stereotactic radiosurgery systems: TrueBeam STx using VMAT and Gamma Knife (GK). Ten patients with 24 tumors (seven with 1-2 and three with 4-6 ranging from 0.1 to 20.2 cc), previously treated with GK Model 4C (prescription doses ranging from 14-23 Gy), were re-planned for VMAT using Eclipse treatment planning system. Various photon beam energies and MLC leaf widths with and without jaw tracking were studied to achieve optimal plans. Plan qualities were assessed by target coverages using Paddick Conformity Index (PCI), normal-brain-tissue integral dose (Gy-cc) and sparing. In all cases critical structure dose criteria were met. The average PCI was 0.76±0.21 for VMAT and 0.46±0.20 for GK plans (p≤0.001), respectively. On average 81% reduction of 12 Gy normal-brain-tissue volumes was achieved by VMAT. The average integral dose ratio of GK to VMAT plans was 1.50±0.61 (p=0.006). VMAT was capable of producing higher quality treatment plans in terms of target coverage and normal brain tissue sparing than GK while using optimal beam geometries and optimization techniques.
我们比较了两种颅内立体定向放射治疗系统（TrueBeam STx 使用容积调强弧形治疗技术（VMAT）和伽玛刀（GK））基于靶区覆盖和正常脑组织保护的治疗计划质量。10 例患有 24 个肿瘤的患者（7 例肿瘤数量为 1 - 2 个，3 例肿瘤数量为 4 - 6 个，肿瘤体积从 0.1 到 20.2 立方厘米），之前接受过 GK 4C 型治疗（处方剂量范围为 14 - 23 戈瑞），使用 Eclipse 治疗计划系统重新进行 VMAT 计划。研究了各种光子束能量以及有无颌骨跟踪的多叶准直器叶片宽度，以实现优化计划。通过使用帕迪克适形指数（PCI）评估靶区覆盖、正常脑组织积分剂量（戈瑞 - 立方厘米）和保护情况来评估计划质量。在所有情况下均满足关键结构剂量标准。VMAT 计划的平均 PCI 为 0.76±0.21，GK 计划的平均 PCI 为 0.46±0.20（p≤0.001）。VMAT 使 12 戈瑞正常脑组织体积平均减少了 81%。GK 计划与 VMAT 计划的平均积分剂量比为 1.50±0.61（p = 0.006）。在使用最佳射束几何形状和优化技术时，VMAT 在靶区覆盖和正常脑组织保护方面能够生成比 GK 更高质量的治疗计划。
