高分辨多叶准直器HD-MLC的Edge加速器TPS模型建立及测试

目的 探讨配备HD-MLC的Edge加速器Eclipse模型建立与测试。方法 利用Razor、CC13采集小野百分深度剂量、离轴曲线、输出因子并与标准数据比对。使用EBT3、EPID、 SRS1000&SRS1500测量MLC半影、穿射漏射、凹凸槽、到位准确性、DLG,并根据测试例γ通过率选出最佳DLG/透射率值。利用 FC65-G对规则野、IMRT、VMAT病例行点剂量验证。使用Octavius 4D及EBT3对测试例行面剂量验证。结果 实测PDD与标准数据一致。3、4 cm射野半影较标准值小,6 cm的较标准值大。所有方野左右边界、射野大小、射野中心偏差分布为-1.0~0.4 mm、0.2~1.7 mm、-0.3~1.9 mm、-0.1~0.8 mm。左、右MLC在不同位置处的半影平均值分别为(2.5±0.042)、(2.7±0.005) mm;MLC透射率分布为 0.009~0.016。测得的DLG、透射因子分别为0.1861 cm、0.0116,最佳DLG、透射因子分别为0.015 cm、0.014。除 1例位于低剂量区外,其余所有测试点剂量偏差均位于 ±3%内。IMRT面剂量验证局部、全局γ通过率分别为 79.81%~100%、96.3%~100%(3%/3 mm),VMAT病例上述通过率分别为 71.3%~98.9%、94.3%~99.8%。结论 本研究方法能准确地实施HD-MLC&Edge系统Eclipse模型建立与测试。

Commissioning and testing of treatment planning system model of an Edge accelerator with a high-definition multi-leaf collimator

Objective To investigate the commissioning and testing of the Eclipse model of an Edge accelerator with high-definition multi-leaf collimator (HD-MLC).Methods The percentage depth dose (PDD), profile, output factor measured by Razor and CC13 were statistically compared with the standard data. Penumbra, transmission factor (TF), leakage, concave-convex groove, accuracy of movement and dosimetry leaf gap (DLG) were measured with EBT3, electronic portal image device (EPID) and PTW SRS1000&SRS1500. The optimal DLG/TF was acquired when the γ pass rate of test cases was the highest. The point dose of regular fields, intensity-modulated radiation therapy (IMRT) and volume-modulated radiation therapy (VMAT) was verified with FC65-G. The planar dose of these case was verified with Octavius 4D and EBT3.Results The measured PDD data were consistent with the standard data. The measured penumbra of 3 cm and 4 cm square fields was smaller, whereas that of 6 cm square field was larger than the standard values. The left and right edge, field size, center of the field were distributed within the range of -1.0-0.4 mm、0.2-1.7 mm,-0.3-1.9 mm and -0.1-0.8 mm, respectively. The mean penumbra of the left and right MLC in different positions were (2.5±0.042) mm and (2.7±0.005) mm. The leakage of MLC was 0.009-0.016. The measured DLG/TF was 0.1861 cm/0.0116 and the optimal DLG/TF was 0.015 cm/0.014. The differences of point dose of all the test cases except the one which was in the low-dose area were within ±3%. Local and global γ pass rates of all IMRT were 79.81%-100% and 96.3%-100% (3%/3 mm), 71.3%-98.9% and 94.3%-99.8% for VMAT cases.Conclusions This method can accurately test and commission the Eclipse treatment planning model of Edge Linac equipped with HD-MLC.