Department of Radiotherapy, Apollo Specialty Hospital, Chennai -600035, India.
J Appl Clin Med Phys. 2012 Sep 6;13(5):3864. doi: 10.1120/jacmp.v13i5.3864.
Prolonged treatment execution time is a concern in CyberKnife robotic radiosurgery. Beam reduction and node reduction technique, and monitor unit optimization methods are adopted to reduce the treatment time. Usage of single collimator in the CyberKnife treatment plan can potentially reduce collimator exchange time. An optimal single collimator, which yields an acceptable dose distribution along with minimum number of nodes, beams, and monitor units, can be a versatile alternative for shortening treatment time. The aim of the present study is to find the optimal single collimator in CyberKnife treatment planning to shorten the treatment time with the acceptable dose distribution. A spherical planning target volume PTV1 was drawn in an anthropomorphic head and neck phantom. Plans with same treatment goals were generated for all the 12 collimators independently. D(95%) was selected as the prescribing isodose and the prescribed dose was 10 Gy. The plan of the optimal collimator size was evaluated for conformity, homogeneity, and dose spillage outside the target. The optimum collimator size and the target dimensions were correlated. The study was repeated with two other target volumes PTV2 and PTV3 for generalizing the results. Collimator sizes just above the diameter of the spherical PTVs were yielding least number of nodes and beams with acceptable dose distributions. The collimator size of 35 mm is optimum for the PTV1, whose diameter is 31.4 mm. Similarly, 50 mm collimator is optimum for PTV2 (diameter= 45.2 mm) and 20 mm collimator is optimum for PTV3 (Diameter = 17.3 mm). The total number of monitor units is found to reduce with increasing collimator size. Optimal single collimator is found to be useful for shortening the treatment time in spherical targets. Studies on two clinical targets, (a brain metastasis and a liver metastasis cases) show comparable results with the phantom study.
在 CyberKnife 机器人放射外科中，治疗执行时间延长是一个关注点。可以采用减少射束和节点数量以及优化监测单位的方法来缩短治疗时间。在 CyberKnife 治疗计划中使用单个准直器可以潜在地减少准直器更换时间。一个最佳的单准直器，可以产生可接受的剂量分布，同时具有最小数量的节点、射束和监测单位，是缩短治疗时间的多功能替代方案。本研究的目的是在 CyberKnife 治疗计划中找到最佳的单准直器，以在可接受的剂量分布下缩短治疗时间。在人体头颈部模型中绘制了一个球形计划靶区（PTV1）。为每个 12 个准直器独立生成具有相同治疗目标的计划。选择 D（95％）作为规定等剂量线，规定剂量为 10 Gy。评估了最佳准直器尺寸的计划的适形性、均匀性和靶区外剂量泄漏。对目标尺寸和最佳准直器尺寸进行了相关性分析。对另外两个靶区 PTV2 和 PTV3 进行了研究，以推广结果。直径略大于球形 PTV 直径的准直器可产生具有可接受剂量分布的最少节点和射束数量。对于 PTV1（直径为 31.4mm），35mm 的准直器是最佳的；对于 PTV2（直径为 45.2mm），50mm 的准直器是最佳的；对于 PTV3（直径为 17.3mm），20mm 的准直器是最佳的。随着准直器尺寸的增加，监测单位的总数减少。研究表明，对于球形靶区，最佳的单准直器可用于缩短治疗时间。对两个临床靶区（脑转移和肝转移病例）的研究结果与模型研究相似。
