Department of Radiation Oncology, Apollo Speciality Hospital, Chennai, India.
J Neurooncol. 2012 Feb;106(3):637-42. doi: 10.1007/s11060-011-0703-5. Epub 2011 Sep 4.
A dosimetric comparison of linear accelerator (LA)-based (BrainLAB) and robotic radiosurgery (RS) (CyberKnife) systems for acoustic schwannoma (Acoustic neuroma, AN) was carried out. Seven patients with radiologically confirmed unilateral AN were planned with both an LA-based (BrainLAB) and robotic RS (CyberKnife) system using the same computed tomography (CT) dataset and contours. Gross tumour volume (GTV) was contoured on post-contrast magnetic resonance imaging (MRI) scan [planning target volume (PTV) margin 2 mm]. Planning and calculation were done with appropriate calculation algorithms. The prescribed isodose in both systems was considered adequate to cover at least 95% of the contoured target. Plan evaluations were done by examining the target coverage by the prescribed isodose line, and high- and low-dose volumes. Isodose plans and dose volume histograms generated by the two systems were compared. There was no statistically significant difference between the contoured volumes between the systems. Tumour volumes ranged from 380 to 3,100 mm(3). Dose prescription was 13-15 Gy in single fraction (median prescribed isodose 85%). There were no significant differences in conformity index (CI) (0.53 versus 0.58; P = 0.225), maximum brainstem dose (4.9 versus 4.7 Gy; P = 0.935), 2.5-Gy volume (39.9 versus 52.3 cc; P = 0.238) or 5-Gy volume (11.8 versus 16.8 cc; P = 0.129) between BrainLAB and CyberKnife system plans. There were statistically significant differences in organs at risk (OAR) doses, such as mean cochlear dose (6.9 versus 5.4 Gy; P = 0.001), mean mesial temporal dose (2.6 versus 1.7 Gy; P = 0.07) and high-dose (10 Gy) volume (3.2 versus 5.2 cc; P = 0.017). AN patients planned with the CyberKnife system had superior OAR (cochlea and mesial temporal lobe) sparing compared with those planned with the Linac-based system. Further evaluation of these findings in prospective studies with clinical correlation will provide actual clinical benefit from the dosimetric superiority of CyberKnife.
我们对基于线性加速器（LA）的（BrainLAB）和机器人放射外科（RS）（CyberKnife）系统治疗听神经瘤（Acoustic schwannoma，AN）的剂量学进行了比较。对 7 例经影像学证实的单侧 AN 患者，使用相同的 CT 数据集和轮廓线，分别采用基于 LA（BrainLAB）和机器人 RS（CyberKnife）系统进行计划。在对比增强磁共振成像（MRI）扫描上勾画大体肿瘤体积（GTV）[计划靶区（PTV）边界 2mm]。使用适当的计算算法进行计划和计算。两种系统的处方等剂量线被认为足以覆盖至少 95%的勾画靶区。通过检查靶区受规定等剂量线的覆盖情况以及高剂量和低剂量体积来进行计划评估。比较了两种系统生成的等剂量计划和剂量体积直方图。两种系统的勾画体积之间没有统计学差异。肿瘤体积范围为 380-3100mm3。单次分割处方剂量为 13-15Gy（中位数处方等剂量 85%）。适形指数（CI）（0.53 与 0.58；P=0.225）、最大脑干剂量（4.9 与 4.7Gy；P=0.935）、2.5Gy 体积（39.9 与 52.3cc；P=0.238）或 5Gy 体积（11.8 与 16.8cc；P=0.129）无显著差异。在危及器官（OAR）剂量方面，如平均耳蜗剂量（6.9 与 5.4Gy；P=0.001）、平均内侧颞叶剂量（2.6 与 1.7Gy；P=0.07）和高剂量（10Gy）体积（3.2 与 5.2cc；P=0.017），两种系统的计划存在统计学差异。与基于 Linac 的系统相比，计划采用 CyberKnife 系统的 AN 患者具有更好的 OAR（耳蜗和内侧颞叶）保护。在具有临床相关性的前瞻性研究中进一步评估这些发现，将从 CyberKnife 的剂量学优势中获得实际的临床获益。
