目的 探讨不同机架角度和多叶准直器(MLC)角度对容积旋转调强放射治疗(VMAT)及静态调强放射治疗(IMRT)MLC叶片机械到位精度的影响.方法 在Eclipse 15.5治疗计划系统上导入并编辑对应的MLC叶片机械到位精度测试计划,并在瓦里安TrueBeam直线加速器上进行以下投照测试:直接采用与直线加速器匹配的Picket Fence测试计划进行VMAT的MLC叶片机械到位精度测试,测试机架角度包括0°、90°、180°和270°;设置机架角度分别为0°、90°、180°和270°,MLC角度为0°,进行IMRT的MLC叶片机械到位精度测试;设置机架角度分别为90°和270°,MLC角度分别为10°、20°和30°,进行IMRT的MLC叶片机械到位精度测试.采用电子射野影像装置(EPID,针对VMAT和IMRT所有测试)和胶片(仅针对IMRT测试)对测试计划进行投照成像,采用DoseLab Version 7.0 软件(针对 VMAT 和 IMRT 所有测试数据)和 RIT complete Version 6.10 软件(仅针对IMRT测试数据)导入并分析EPID影像的MLC叶片机械到位精度,采用Film QA Pro Version 4.0软件分析胶片的MLC叶片机械到位精度.结果 DoseLab Version 7.0软件针对EPID影像的分析结果显示,4种机架角度下VMAT的MLC叶片机械到位精度平均偏差均＜0.20 mm,设置到位精度容差为0.50 mm,栅栏野通过率为100％;4种机架角度下IMRT的MLC叶片机械到位精度平均偏差均≤0.50 mm,且均大于VMAT的MLC叶片机械到位精度平均偏差,设置到位精度容差为0.50 mm,栅栏野通过率＞95％.RIT complete Version 6.10软件针对EPID影像的分析结果及Film QA Pro Version 4.0软件针对胶片的分析结果均显示,机架角度为90°和270°时,不同MLC角度的MLC叶片机械到位精度平均偏差均＜1mm,符合美国医学物理学家协会(AAPM)TG-142报告要求;且机架角度90°和270°的MLC叶片机械到位精度偏差呈相反趋势.结论 不同机架角度和MLC角度下,VMAT和IMRT的MLC叶片机械到位精度均符合标准.但MLC叶片机械到位精度测试对于放射治疗计划剂量的精准投照至关重要,因此需要严格按照相关标准定期进行质量控制测试,检查叶片到位的精度及重复性.
The Influence of Different Gantry Angles and Multi-Leaf Collimator Angles on the Leaf Mechanical Positioning Accuracy of Multi-Leaf Collimator
Objective To explore the effects of different gantry angles and multi-leaf collimator(MLC)angles on the MLC leaf mechanical positioning accuracy in volume modulated arc therapy(VMAT)and intensity modulated radiation therapy(IMRT).Methods On the Eclipse 15.5 treatment planning system,the corresponding MLC blade mechanical positioning accuracy testing plan is imported and edited.Meanwhile,on the Varian TrueBeam linear accelerator,the following irradiation trial were conducted.The Picket Fence test plan matching the linear accelerator was directly used to test the MLC leaf mechanical position accuracy in VMAT,with the test gantry angles including 0°,90°,180° and 270°;The gantry angles were set to 0°,90°,180°,and 270° respectively,and the MLC angle was set to 0° for IMRT MLC leaf mechanical positioning accuracy testing;The rack angles were set to 90° and 270°,and the MLC angles were set to 10°,20°,and 30°,respectively,for IMRT MLC blade mechanical positioning accuracy testing.The electronic portal imaging device(EPID,for all VMAT and IMRT tests)and film(for IMRT tests only)were used for projection imaging of the test plan.The DoseLab Version 7.0 software(for all VMAT and IMRT test data)and RIT complete Version 6.10 software(for IMRT test data only)were used to import and analyze the MLC leaf mechanical positioning accuracy of EPID images,and Film QA Pro Version 4.0 software was used to analyze the MLC leaf mechanical positioning accuracy of films.Results The analysis results of DoseLab Version 7.0 software for EPID images showed that the average deviation of mechanical positioning accuracy of VMAT MLC leaves with four gantry angles was less than 0.20 mm.The positioning accuracy tolerance was set to 0.50 mm,and the fence field pass rate was 100％;The average deviation of the mechanical positioning accuracy of IMRT MLC leaf at four different rack angles was≤0.50 mm,and was greater than the average deviation of VMAT MLC leaf mechanical positioning accuracy.The positioning accuracy tolerance was set to 0.50 mm,and the fence field pass rate was greater than 95％;The analysis results of RIT complete version 6.10 software for EPID images and Film QA Pro version 4.0 software for film both showed that when the gantry angle was 90° and 270°,the average deviation of mechanical positioning accuracy of MLC leaves at different MLC angles was less than 1 mm,which meets the requirements of the American Association of Physicists in Medicine(AAPM)TG-142 report;The mechanical positioning accuracy deviation of MLC leaves with gantry angles of 90 ° and 270 ° showed an opposite trend.Conclusions With different rack angles and MLC angles,the mechanical positioning accuracy of VMAT and IMRT MLC leaves met the standards.However,the accuracy testing of MLC leaf mechanical positioning was crucial for precise dose projection in radiation therapy plans.Therefore,it was necessary to strictly follow relevant standards for regular quality control tests to check the accuracy and repeatability of leaf positioning.
GantryMulti-leaf collimatorAngleLeavesPositioning accuracyQuality control
万方数据
维普
