Department of Radiation Oncology, University of California, San Francisco, California, USA.
J Neurosurg. 2010 Dec;113 Suppl:199-206.
The Leksell Gamma Knife and the Accuray CyberKnife systems have been used in the radio surgical treatment of trigeminal neuralgia. The 2 techniques use different delivery methods and different treatment parameters. In the past, CyberKnife treatments have been associated with an increased incidence of treatment-related complications, such as facial numbness. The goal of this study was to develop a method for planning a CyberKnife treatment for trigeminal neuralgia that would reproduce the dosimetric characteristics of a Gamma Knife plan. A comparison between Gamma Knife and CyberKnife treatment plans obtained with this method is presented.
Five patients treated using the Gamma Knife Perfexion Unit were selected for this study. All patients underwent CT cisternography to accurately identify the position of the trigeminal nerve. The Gamma Knife plans used either one 4-mm-diameter collimator or two coincident 4-mm collimators (one open and one with sector blocking) placed at identical isocenter coordinates. A maximum local dose of 80 Gy was prescribed. Critical structures and representative isodose lines were outlined in GammaPlan and exported to the CyberKnife treatment planning platform. CyberKnife treatments were developed using the 5-mm-diameter cone and the trigeminal node set, which provides an effective collimation diameter of 4 mm at the isocenter. The 60-Gy isodose volume imported from GammaPlan was used as the target in the CyberKnife plans. The CyberKnife treatments were optimized to achieve target dose and critical structure sparing similar to the Gamma Knife plans. Isocentric and nonisocentric delivery techniques were investigated. Treatment plans were compared in terms of dosimetric characteristics, delivery, and planning efficiency.
CyberKnife treatments using the 5-mm cone and the trigeminal node set can closely reproduce the dose distribution of Gamma Knife plans. CyberKnife isocentric and nonisocentric plans provide comparable results. The average length of the trigeminal nerve receiving a dose of 60 Gy was 4.5, 4.5, and 4.4 mm for Gamma Knife, nonisocentric CyberKnife, and isocentric CyberKnife, respectively. However, minimizing the dose to the critical structures was more difficult with the CyberKnife and required the use of tuning structures. In addition, the dose fall off away from the target was steeper in Gamma Knife plans, probably due to the larger number of beams (192 beams for perfexion vs ~ 100 beams for cyberknife). While the treatment time with the cyberknife is generally shorter, the planning time is significantly longer.
CyberKnife radiosurgical parameters can be optimized to mimic the dose distribution of Gamma Knife plans. However, Gamma Knife plans result in superior sparing of critical structures (brainstem, temporal lobe,and cranial nerves VII and VIII) and in steeper dose fall off away from the target. The clinical significance of these effects is unknown. (DOI: 10.3171/2010.8.GKS101002)
Leksell 伽玛刀和 Accuray 射波刀系统已用于治疗三叉神经痛的放射外科手术。这两种技术使用不同的输送方法和不同的治疗参数。过去，射波刀治疗与治疗相关并发症的发生率增加有关，如面部麻木。本研究的目的是开发一种用于规划射波刀治疗三叉神经痛的方法，该方法可复制伽玛刀计划的剂量特征。本文介绍了使用该方法获得的伽玛刀和射波刀治疗计划之间的比较。
选择了 5 名使用伽玛刀 Perfexion 治疗的患者进行本研究。所有患者均接受 CT 脑池造影术，以准确确定三叉神经的位置。伽玛刀计划使用一个 4 毫米直径的准直器或两个重合的 4 毫米准直器（一个开放，一个用扇形阻挡），放置在相同的等中心坐标。规定最大局部剂量为 80Gy。在 GammaPlan 中勾勒出关键结构和代表性等剂量线，并将其导出到射波刀治疗计划平台。使用 5 毫米直径的圆锥体和三叉神经节设置开发射波刀治疗，在等中心处提供有效准直直径为 4 毫米。从 GammaPlan 导入的 60Gy 等剂量体积用作 CyberKnife 计划的目标。优化 CyberKnife 治疗以实现类似于伽玛刀计划的目标剂量和关键结构保护。研究了等中心和非等中心输送技术。根据剂量学特征、输送和规划效率对治疗计划进行了比较。
使用 5 毫米圆锥体和三叉神经节设置的 CyberKnife 治疗可以很好地复制伽玛刀计划的剂量分布。射波刀等中心和非等中心计划提供了可比的结果。接受 60Gy 剂量的三叉神经的平均长度分别为 4.5、4.5 和 4.4mm，分别为伽玛刀、非等中心 CyberKnife 和等中心 CyberKnife。然而，使用 CyberKnife 更难以最小化关键结构的剂量，需要使用调谐结构。此外，伽玛刀计划中远离目标的剂量下降更为陡峭，这可能是由于光束数量较多（适形治疗的光束为 192 个，而射波刀的光束约为 100 个）。虽然射波刀的治疗时间通常较短，但规划时间明显更长。
可以优化射波刀放射外科参数以模拟伽玛刀计划的剂量分布。然而，伽玛刀计划可更好地保护关键结构（脑干、颞叶和颅神经 VII 和 VIII），并使目标外的剂量下降更陡峭。这些影响的临床意义尚不清楚。（DOI：10.3171/2010.8.GKS101002）
