摘要
Abstract
Objective:To study the influence of image panel of different source image distances(SID)of beam central axis of Portal Dosimetry(PD)dose verification system on the verification of volumetric modulated arc therapy(VMAT)plan,so as to provide reference for dose verification in selecting the appropriate SID position and evaluation criteria.Methods:From July 2022 to May 2024,10 patients,who received radiotherapy on tumor at different-site in Specialized Medical Center of the Chinese People's Armed Police Force,were selected.All patients underwent VMAT.Ten simulated dose verification plans were established according to the data of patients,with a total of 10 arcs.The non-crystalline silicon image panel was calibrated at 0,-30,-40,-50 and-60 cm from the isocenter on the beam central axis,and the verification plans of PD system were established.Dose verification was carried out using electronic portal imaging device(EPID)(a-Si EPID)of non-crystalline silicon image panel that was onboard by accelerator.The γ pass rates under the standards of 3%/3 mm and 3%/2 mm were compared and analyzed.Results:Under the evaluation standard of 3%/3 mm,the γ pass rates of the collected doses were(98.93±0.81)%,(94.77±9.00)%,(92.18±11.34)%,(89.72±12.54)%and(87.05±13.06)%when the SID values were respectively 100,130,140,150 and 160 cm,which were all higher than these under the evaluation standard of 3%/2 mm,and the differences were statistically significant(t=2.75,3.44,3.59,4.16,6.47,P<0.05).There were significant differences between the average γ pass rate of the collected dose under evaluation standards of 3%/3 mm and 3%/2 mm when SID was 100cm,and the 100%of γ pass rate(t=-3.21,-3.62,P<0.05),while the differences of the obtained γ pass rates among other SID positions were not statistically significant(P>0.05).Conclusion:Under the evaluation standards of 3%/3 mm and 3%/2 mm,the γ pass rate of the collected dose at SID 100 cm is the highest.The γ pass rate of the collected dose at SID 130 cm can meet the basically clinical requirements.In EPID dose verification,the collection for dose should be prioritized for selection when SID was 100 cm,and the γ pass rate of dose verification is higher,the influence of interference is less at this time,which verification results have higher credibility.关键词
不同源图像距离/剂量验证/非晶硅影像面板/γ通过率/容积旋转调强放射治疗(VMAT)Key words
Different source image distances/Dose verification/Non-crystalline silicon image panel/γ pass rate/Volumetric modulated arc therapy(VMAT)分类
医药卫生
