医用加速器TrueBeam剂量输出长期稳定性研究

目的：分析并研究瓦里安公司新型直线加速器TrueBeam型号光子束的长期稳定性。方法：采用Standard Imaging公司的QA BeamChecker Plus采集TrueBeam系统6 MV光子线长期日检数据,并进行系统性分析,评价参数包括中心轴剂量、平坦度及对称性。结果：18个月的日检数据分析结果显示,6 MV的X射线中心轴剂量偏差为（0.0%±0.7%）,仅1次检测结果〉2%;平坦度稳定性好,偏差为（0.1%±0.1%）;轴向对称性偏差和横向对称性偏差测量结果均在±1%以内。结论：TrueBeam医用加速器系统的6 MV光子束具有非常稳定的剂量输出特性。

Evaluation of dose delivery stability of a new linear accelerator TrueBeam

Objective： To study the long-term stability of 6MV photon beam on TrueBeam, which is a new linear accelerator introduced by Varian Medical System. Methods： QA BeamChecker Plus（QABC＋, Standard Imaging Inc., Middleton, USA） was used to measure 6MV X-ray on TrueBeam linac as daily quality assurance（Daily QA）. Dosimetric parameter, including output Constancy, flatness and symmetry, were employed to evaluate the dose delivery stability of TrueBeam linac. Results： Daily QA results of 18 months showed the dose output delta was（0.0%±0.7%）, only once out of tolerance of 2%. The constancy of Flatness was excellent with the delta of（0.1%±0.1%）. The symmetric of axial and transverse varied within 1%. Conclusion：The output constancy of TrueBeam with 6MV is very stable, as well as flatness and symmetry. It＇s stable and reliable to implement Truebeam linear accelerator in clinical.