射波刀VSI系统的主要性能测试

Performance Evaluation of a CyberKnife VSI^TM System

目的测试射波刀VSI系统实施立体定向放疗的准确性和可靠性。方法对射波刀VSI系统的机器人系统、患者定位系统、目标定位系统、加速器系统、可变准直器系统5个子系统的性能分别进行测试，记录机器人系统机械臂到位精度、患者定位系统的床到位精度、目标定位系统的追踪精度、加速器系统相关剂量学参数和可变准直器系统重复性。对射波刀VSI系统综合投照精度进行端到端（E2E）的系统测试。结果机器人系统所有节点机械臂运动的平均到位偏差≤0．1 mm，单个节点最大到位偏差≤O．29 mm。可变准直器系统所有尺寸孔径重复性误差≤0．28 mm。床到位精度与追踪精度均〈0．2 mm和0．5°。固定和可变2种类型准直器系统激光束与辐射射束中心偏差≤0．4 mm。6 mV射线的射线质与离轴比曲线等参数均在正常范围内。射波刀剂量输出稳定性、线性与随射束角度变化的差异均〈1．0％。固定和可变2种类型准直器的透射因子均〈0．4％。射波刀VSI系统综合投照精度的E2E测试最大偏差为0．87 mm。结论射波刀VSI系统能够准确、精确地实施立体定向放疗。

Objective To evaluate the accuracy and reliability of the CyberKnife VSI system for stereotactic radiotherapy. Methods First, the mechanical accuracy of the robotic manipulator system, the repeatability of the Iris variable aperture collimator system, the couch position accuracy of the patient positioning system, the tacking precision of the target locating system and the dosimetric beam characteristics of the linac system for each subsystem of CyberKnife VSI system were tested. Finally, the total beam delivery precision of the CyberKnife VSI system was evaluated. Results The mean positioning deviations of the mechanical arm movement of the robotic manipulator system were less than 0. 1 ram, and the maximum positioning deviation of single note was ≤0. 29 mm. The repeatability of the aperture sizes for the Iris variable aperture collimator system was ≤0. 28 mm. The couch position accuracy of the patient positioning system was〈0. 2 mm and the tracking precision of the target locating system was less than 0. 5% The linac beam-laser beam axes coincidence between the Iris and fixed collimators was better than 0. 4 ram. The 6-MV beam parameters, such as beam quality and profile, were found within the acceptance limits. The deviations of output reproducibility, linearity and constancy versus linac orientation were less than 1.0%. The transmission factors of two types of collimators were lower than 0.4%. End-to-end test demonstrated that the maximum deviation of the total delivery precision of CyberKnife VSI system was 0. 87 mm. Conclusion The CyberKnife VSI system is accurate and reliable for stereotactic radiotherapy.