Huss Marie, Barsoum Pierre, Dodoo Ernest, Sinclair Georges, Toma-Dasu Iuliana
Stockholm University.
J Appl Clin Med Phys. 2015 Nov 8;16(6):3-16. doi: 10.1120/jacmp.v16i6.5255.
Stereotactic radiosurgery using Gamma Knife (GK) or linear accelerators has been used for decades to treat brain tumors in one fraction. A new positioning system, Extend™, was introduced by Elekta AB for fractionated stereotactic radiotherapy (SRT) with GK. Another option for fractionated SRT is advanced planning and delivery using linacs and volumetric modulated arc therapy (VMAT). This project aims to assess the performance of GK Extend™ for delivering fractionated SRT by comparing GK treatments plans for brain targets performed using Leksell GammaPlan (LGP) with VMAT treatment plans. Several targets were considered for the planning: simulated metastasis- and glioma-like targets surrounding an organ at risk (OAR), as well as three clinical cases of metastases. Physical parameters such as conformity, gradient index, dose to OARs, and brain volume receiving doses above the threshold associated with risk of damaging healthy tissue, were determined and compared for the treatment plans. The results showed that GK produced better dose distributions for target volumes below 15 cm3, while VMAT results in better dose conformity to the target and lower doses to the OARs in case of fractionated treatments for large or irregular volumes. The volume receiving doses above a threshold associated with increased risk of damage to normal brain tissue was also smaller for VMAT. The GK consistently performed better than VMAT in producing a lower dose-bath to the brain. The above is subjected only to margin-dependent fractionated radiotherapy (CTV/PTV). The results of this study could lead to clinically significant decisions regarding the choice of the radiotherapy technique for brain targets.
使用伽玛刀（GK）或直线加速器的立体定向放射外科已被用于一次性治疗脑肿瘤数十年。Elekta AB公司推出了一种新的定位系统Extend™，用于伽玛刀的分次立体定向放射治疗（SRT）。分次SRT的另一种选择是使用直线加速器和容积调强弧形治疗（VMAT）进行先进的计划和实施。该项目旨在通过比较使用Leksell GammaPlan（LGP）制定的脑靶区GK治疗计划与VMAT治疗计划，评估GK Extend™在实施分次SRT方面的性能。计划中考虑了几个靶区：模拟的转移瘤样和胶质瘤样靶区，周围有危及器官（OAR），以及三例转移瘤的临床病例。确定并比较了治疗计划的物理参数，如适形度、梯度指数、OAR的剂量，以及接受高于与损伤健康组织风险相关阈值剂量的脑体积。结果表明，对于体积小于15 cm³的靶区，GK产生的剂量分布更好，而在对大体积或不规则体积进行分次治疗时，VMAT导致靶区剂量适形性更好，OAR的剂量更低。VMAT中接受高于与正常脑组织损伤风险增加相关阈值剂量的体积也更小。在对脑产生较低剂量浴方面，GK始终比VMAT表现更好。以上仅适用于基于边缘的分次放射治疗（CTV/PTV）。本研究结果可能会导致关于脑靶区放射治疗技术选择的具有临床意义的决策。
