Performance Evaluation of a CyberKnife VSITM System / 中华放射肿瘤学杂志

ABSTRACT

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 mm,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 mm.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.