探测器阵列在TPS模型调整中的应用

Application of detector array in treatment planning system modeling adjustment

目的 探讨探测器阵列在Monaco模型MLC参数调整中的应用可行性.方法 先固定其中一个参数,再改变另一个参数,评估参数变化对测试野3ABUT、7SegA及FOUR L γ通过率影响,确定MLC参数leaf transmission与leaf offset.测试中对随机选择的12例不同解剖部位的肿瘤病例,用Octavius 4D系统分别进行Step ＆ Shot与dMLC计划的二维剂量验证（机架角归零）和VMAT计划的三维剂量验证,以3%/3 mm的标准分析γ通过率.再分别对三种调强计划进行点剂量验证分析其剂量偏差.结果 确定leaf transmission、leaf offset参数值为0.01、-0.08 mm.模型调整前后,三种调强计划剂量分布验证平均通过率分别为（88.59±2.94）%、（87.81±3.28）%、（87.45±2.24）%和（98.45±1.23）%、（98.90±1.01）%、（96.03±1.66）%,点剂量验证平均剂量偏差分别为（0.85±0.75）%、（0.95±0.39）%、（0.98±0.40）%和（0.97±0.57）%、（1.08±0.76）%、（0.86±0.45）%.结论Octavius729探测器阵列应用于Monaco模型中MLC参数的调整是可行且可靠的.

Objective To investigate the feasibility of detector array in Monaco modeling for MLC parameters adjustment.Methods One parameter was fixed, and then the other parameter was changed.The γ pass rates of the test beams, namely 3ABUT, 7SegA, and FOUR L, were assessed to determine the values of leaf transmission and leaf offset.A total of 12 tumor cases from different anatomical sites were randomly selected.Two-dimensional dose verification （rack angle zero） of Step ＆ Shot and dMLC plans as well as three-dimensional dose validation of VMAT plan were performed using Octavius 4D system.The γ pass rates were analyzed at a standard of 3%/3 mm.Meanwhile, the point dose verification for these three plans was analyzed to obtain the dose deviations.Results The values of leaf transmission and leaf offset were 0.0105 and-0.08 mm, respectively.The average γ pass rates （%） of Step＆amp; Shot, dMLC, and VMAT plans were 88.59±2.94, 87.81±3.28, and 87.45±2.24 before adjustment and 98.45±1.23, 98.9±1.01, and 96.03±1.66 after adjustment.In addition, the average dose deviations （%） according to the point dose verification were 0.85±0.75, 0.95±0.39, and 0.98±0.40 before adjustment and 0.97±0.57, 1.08±0.76, and 0.86±0.45 after adjustment.Conclusions Octavius detector 729 ionization chamber array is a feasible and reliable device in Monaco modeling for MLC parameters adjustment.