VMAT模式下MLC叶片运动速度对到位误差影响  

Effect of Leaf Movement Speed on Setup Error of Multileaf Collimator in Volumetric Modulated arc Therapy Mode

作　　者：王广善 杨波[2] 庞廷田[2] 孙显松 邱杰[2] 

机构地区：[1]首都医科大学附属北京胸科医院放疗科,北京101149 [2]中国医学科学院北京协和医学院北京协和医院放疗科,北京100730

出　　处：《结核病与胸部肿瘤》2017年第3期217-221,共5页Tuberculosis and Thoracic Tumor

摘　　要：目的探讨RapidArc模式下MLC叶片运动速度对叶片到位误差的影响，完善RapidArcQA方案，验证RapidArc可靠性。方法参考PicketFenceStmic_M120．dcm、PicketFenceRA_M120．dcm文件，设计模拟相邻叶片不同速度的Tilt测试，分析EPID图像得出叶片到位误差。结果静态机架和RapidArc模式下，Tilt测试中gap11-gap50的位置误差都逐渐增大。机架270。时gap41误差最大，为-0．55mm。RapidArc模式下gap46误差最大，为-0．67min。所有模式下gap宽度偏差均≤15％。对比4个固定机架角度的宽度偏差图形几乎相似，每个条纹相同gap处宽度偏差呈现一致趋势。与静态机架模式下gap宽度偏差百分比相比，RapidArc模式下的波动更大。结论随MLC叶片速度增加，到位误差随之增大。叶片速度不同并未对gap宽度造成明显影响，不同叶片速度形成的gap宽度偏差无规律。4个固定机架角度下gap宽度偏差图像相似，说明gap宽度偏差与叶片本身有关，与机架所处角度几乎无关。RapidArc模式比固定机架模式对gap宽度影响更大。Objective To study the effect of leaf movement speed on the setup error of multileaf collimator （MLC） in RapidArc mode, and to improve quality assurance and verify the reliability of RapidArc. Methods Referring to the PicketFenceStatic_M120.dcm and PicketFenceRA_M120.dcm files, the Tilt tests with different adjacent leaf speed were designed and setup errors of MLC were obtained by analyzing electronic portal imaging device images. Results In the Tilt tests, the setup errors gradually increased from gapll to gap50 in both static gantry mode and RapidArc mode. With a gantry angle of 270°, gap41 had the maximum setup error of-0.55 mm. In the RapidArc mode, gap46 had the maximum setup error of - 0.67 mm. The deviation of gap width was no greater than 15% in any mode. There was no significant difference in deviation pattern of gap width between four modes with different gantry angles. The same gaps in different stripes showed a consistent trend in gap width. The RapidArc mode had a larger variation in percentage deviation of gap width than the static gantry mode. Conclusions The setup error increases with the increase in the speed of MLC leaf. The variation in the leaf speed has no significant impact on the gap width. There is no correlation between the leaf speed and the deviation of gap width. Four different gantry angles give similar deviation patterns of gap width, suggesting that the deviation of gap width is related to the leaf rather than the gantry angle. The RapidArc mode has a greater impact on the gap width than the fixed gantry mode.

关 键 词：容积调强弧形疗法 多叶准直器 到位误差 

分 类 号：R493[医药卫生—康复医学]