射野孔径形状控制器对直肠癌快速容积旋转调强放射治疗计划质量、机器传输能力和准确性的影响研究

目的:研究Eclipse15.5治疗计划系统中射野孔径形状控制器(ASC)对直肠癌快速(RapidArc)容积旋转调强放射治疗(VMAT)计划质量、机器传输能力和剂量传输准确性的影响。方法:选取医院收治的20例直肠癌患者,对每个病例生成ASC"off"、ASC"verylow"、ASC"moderate"和ASC"veryhigh"共4组RapidArc对照计划。其中ASC调节等级分别设置为关闭(off)、非常低(verylow)、中等(moderate)和非常高(veryhigh),其他计划参数设置保持一致,使用射野剂量系统(PD)验证剂量传输的准确性。主要评价指标包括剂量体积直方图(DVH)、Paddick适形指数(PCI)、梯度指数(GI)、均质性指数(HI)、剂量率(DoseRate)、机架转速(GantrySpeed)、机器跳数(MUs)、每角度机器跳数(MU/deg)和Gamma通过率,采用单因素方差分析和Kruskal-Wallis秩和检验检测4组ASC计划之间各项统计指标的差异。结果:4组ASC计划间除计划靶区平均剂量(PTV D_med)差异有统计学意义(F=3.243,P=0.027)外,其他DVH、PCI、GI和HI指标差异均无统计学意义。机器传输能力中ASC为very low、moderate和very high的MUs较off分别下降14.4%、20.9%和29.6%。4组计划间DoseRate、MU/deg和MUs差异有统计学意义(x²=16.621,x²=16.007,x²=15.877;P=0.001)。剂量传输准确性中4组计划间3%/3 mm和2%/2 mm的Gamma通过率差异均无统计学意义。结论:计划设计过程中需考虑ASC对各项计划指标的影响,应根据计划的复杂性和临床需要调整ASC的等级。

A study on the influence of ASC of radiation field on the quality,transmission ability of machine and accuracy of RA VMAT plan of rectal cancer

Objective:To study the influence of the aperture shape controller(ASC)in the treatment planning system of Eclipse 15.5 version on the quality,transmission ability of machine and transmission accuracy of dose of rapid arc(RA)volumetric modulated arc therapy(VMAT)plan of rectal cancer.Methods:Twenty patients with rectal cancer admitted to hospital were selected,and 4 groups of Rapid Arc control plans were generated for each case:ASC"off",ASC"very low",ASC"moderate"and ASC"very high".The ASC adjustment levels were set to"off","very low","moderate"and"very high"respectively.And the settings of other plan parameters were kept the same,and the portal dosimetry(PD)system was used to verify the accuracy of dose delivery.The main evaluation indicators included dose volume histogram(DVH),Paddick’s conformity index(PCI),gradient index(GI),homogeneity index(HI),dose rate,gantry speed,monitor units(MUs),monitor units per degree(MU/deg)and Gamma pass rate.One-way ANOVA analysis of variance and Kruskal-Wallis rank sum test were used to test differences of various statistical indicators between the 4 groups of ASC plans.Results:The test results showed that the difference of PTV D_med between the 4 groups of ASC plans was statistically significant(F=3.243,P=0.027),but there were no significant differences in other indicators included DVH,PCI,GI and HI.In terms of machine transmission ability,the MUs with ASC of"very low","moderate"and"very high"decreased by 14.4%,20.9%and 29.6%respectively which compared with ASC of"off".The differences of dose rate,MU/deg and MUs between the 4 groups of plans were significant(x²=16.621,x²=16.007,x²=15.877,P=0.001).In terms of dose delivery accuracy,there were no significant differences in the Gamma pass rates of 3%/3 mm and 2%/2 mm between the 4 groups of plans.Conclusion:In the process of plan design,it is necessary to consider the impact of ASC on various plan indicators,and the level of ASC should be adjusted according to the complexity of the plan and the clinical needs.