Barnes Michael, Dipuglia Andrew, Beeksma Brad, Lehmann Joerg
Department of Radiation Oncology, Calvary Mater Hospital Newcastle, Newcastle, New South Wales, Australia.
School of Informational and Physical Sciences, University of Newcastle, Newcastle, New South Wales, Australia.
J Appl Clin Med Phys. 2025 Jul;26(7):e70171. doi: 10.1002/acm2.70171.
To evaluate the Varian machine performance check (MPC) collimator devices check (CDC) for routine MLC and jaw testing as part of an AAPM compliant linac QA program.
CDC MLC positioning, MLC backlash, jaw positioning, and jaw parallelism were each assessed for repeatability and concordance with conventional QA. MLC and jaw positioning were also assessed for sensitivity. Measurement time and repeatability of CDC were assessed by timing and recording five successive measurements on a single linac. Concordance was assessed monthly over 5 months on four linacs, conducted during the same session as conventional QA. MLC positioning was compared to an advanced picket fence test, while jaw positioning and parallelism were compared to department in-house EPID based methods. MLC backlash was compared to the Varian built-in method. Sensitivity was assessed via deliberately introduced errors except for MLC backlash, which was assessed via correlation between methods across leaf banks.
CDC requires 4:09 (min:s) ± 1.8 s (2 SD) to perform. Repeatability was measured to be: 0.02 mm for both MLC positioning and backlash, 0.15 mm for jaw positioning and 0.009° for jaw parallelism (2 SD). Concordance was observed for mean MLC positioning to within 0.32 , 0.08 mm for MLC backlash, 0.6 mm for jaw positioning and 0.06° for jaw parallelism. MLC and jaw positioning sensitivity were observed with maximum mean difference between methods of 0.18 and 0.71 mm, respectively. MLC backlash correlation coefficient between methods across leaf banks was observed to 0.84 and 0.9 for banks A and B, respectively.
MPC CDC has been demonstrated to provide acceptably equivalent MLC and jaw positioning assessment to standard methods and could conceivably be used in a linac QA program for these purposes.
评估瓦里安机器性能检查（MPC）中的准直器设备检查（CDC），用于常规多叶准直器（MLC）和光阑测试，作为符合美国医学物理师协会（AAPM）要求的直线加速器质量保证（QA）程序的一部分。
分别评估CDC的MLC定位、MLC反向间隙、光阑定位和光阑平行度的重复性以及与传统QA的一致性。还评估了MLC和光阑定位的灵敏度。通过在一台直线加速器上计时并记录连续五次测量来评估CDC的测量时间和重复性。在五个月内每月对四台直线加速器进行一致性评估，与传统QA在同一时间段内进行。将MLC定位与先进的栅栏测试进行比较，而光阑定位和平行度与科室内部基于电子射野影像装置（EPID）的方法进行比较。将MLC反向间隙与瓦里安内置方法进行比较。除MLC反向间隙外，通过故意引入误差来评估灵敏度，MLC反向间隙通过跨叶组的方法之间的相关性来评估。
CDC执行需要4分09秒±1.8秒（2标准差）。测量的重复性为：MLC定位和反向间隙均为0.02毫米，光阑定位为0.15毫米，光阑平行度为0.009°（2标准差）。观察到平均MLC定位的一致性在0.32以内，MLC反向间隙为0.08毫米，光阑定位为0.6毫米，光阑平行度为0.06°。观察到MLC和光阑定位的灵敏度，方法之间的最大平均差异分别为0.18和0.71毫米。跨叶组的方法之间MLC反向间隙的相关系数在A组和B组分别为0.84和0.9。
已证明MPC CDC能为标准方法提供可接受的等效MLC和光阑定位评估，并且理论上可用于直线加速器QA程序中的这些目的。
