调强放射治疗计划验证不同伽马通过率评估标准下结果的差异性

Intensity-modulated radiation therapy plans validate differences in outco mes under different gamma pass rate evaluation criteria

目的:分析在不同gamma通过率标准下不同加速器剂量验证结果的差异性,验证调强放射治疗(IMRT)的剂量精度误差。方法:分别分析贵州医科大学附属医院2011年9月至今在不同加速器上执行的1549个调强计划共9786个射野,计划设计使用Pinnacle系统,执行机器为Elekta加速器,型号分别为Precise1343、Precise2444及Synergy2020,剂量验证使用Map Check二维验证设备。对比不同加速器、不同gamma通过率标准(包括3%/3 mm、3%/2 mm、2%/3 mm、2%/2 mm及1%/3 mm)之间的差异。结果:相较于3%/3 mm,2%/3 mm伽马通过率小于90%的射野数占总射野数的1.8%,伽马指数3%/2 mm时则高达19%。Synergy2020加速器伽马通过率大多集中于99%至100%之间,占其总射野数的50.05%,而Precise机型仅为32.28%(Precise1343加速器)和31.03%(Precise2444加速器)。射野跳数与伽马通过率存在相关性(P<0.001,<-0.3)。除2%/2 mm外,不同伽马指数、不同机型的平均射野通过率均大于90%。结论:相较于剂量差异对gamma通过率的影响,距离符合度的影响更大。Synergy加速器各个伽马评估标准下的平均通过率均好于Precise机型。射野跳数与伽马通过率相关性系数具有统计学意义,但相关程度为极弱负相关。

Objective:To analyze the difference of different accelerator dose verification results under different gamma pass rate standards and to verify the dose accuracy error of IMRT.Method:A total of 9,786 shooting fields of 1,549 intensifier plans executed on different accelerators by the Affiliated Hospital of Guizhou Medical University are analyzed from September 2011 to now.The pinnacle system is planned to be designed and implemented by Elekta accelerator.Models are Precise1343,Precise2444 and Synergy2020 respectively.Map Check two-dimensional verification device is used for dose verification.The differences between different accelerators and different gamma pass rates(including 3%/3 mm,3%/2 mm,2%/3 mm,2%/2 mm and 1%/3 mm)were compared.Results:Compared with 3%/3 mm,a 2%/3 mm gamma-ray pass rate of less than 90%accounted for 1.8%of the total gamma-ray field number,and the gamma-ray index was as high as 19.5%when 3%/2 mm.Synergy2020 accelerator gamma pass rate is mostly between 99%and 100%,accounting for 50.05%of its total emission field,while Precise models are only 32.28%(Precise1343 accelerator)and 31.03%(Precise2444 accelerator).There was a correlation between the number of field hops and the gamma pass rate(P<0.001,r_s<-0.3).Except for 2%/2 mm,the average pass rate of different gamma indices and models is more than 90%.Conclusion:The effect of distance coincidence is more significant than dose difference on gamma pass rate.Synergy Accelerator’s average pass rate was better than Precise’s for all gamma evaluation criteria.The correlation coefficient between the jump number and the gamma pass rate was statistically significant,but the correlation degree was feebl e and negative.