宫颈癌调强放射治疗三维在体剂量验证分析及最佳γ通过率阈值

In vivo three-dimensional dose validation for intensity-modulated radiotherapy of cervical cancer and the optimal gamma passing rate threshold

目的:对宫颈癌调强放射治疗(IMRT)进行基于电子射野影像装置的三维在体剂量验证(EIVD)分析,研究测量剂量与计划剂量间的差异,并通过剂量学敏感性探讨EIVD质控中最佳γ通过率阈值。方法:回顾性分析浙江大学医学院附属妇产科医院行IMRT的45例宫颈癌患者,所有患者在治疗过程中行EIVD验证,获取测量剂量。采用2mm/2%、2mm/3%、3mm/3%的全局γ指标进行通过率分析,采用剂量体积直方图参数评估测量剂量和计划剂量之间的差异。通过皮尔逊(Pearson)相关性分析研究γ通过率与剂量学差异间的相关性,绘制受试者工作特征(ROC)曲线确定最佳γ通过率阈值。结果:3类γ指标2mm/2%、2mm/3%、3mm/3%的平均通过率分别为(83.07±5.25)%、(91.69±3.52)%、(95.02±2.46)%;EIVD测量剂量与计划剂量在计划靶区(PTV)的平均剂量(Dmean)偏差为2.43%(P=0.016),膀胱、直肠、小肠的Dmean偏差分别为0.35%、0.46%、0.30%(P>0.05)。Pearson分析显示3类γ指标与PTV的剂量偏差相关性较强(r>0.7),与危及器官相关性较弱(r<0.7);ROC分析显示2mm/2%、2mm/3%、3mm/3%最佳的γ通过率阈值分别为79.06%、90.04%、94.19%。结论:EIVD能够有效保证宫颈癌IMRT过程中PTV剂量传递的精准性,利用γ通过率阈值能够为下一步宫颈癌自适应IMRT提供一定的临床依据。

Objective To analyze the in vivo three-dimensional dose verification using electronic portal imaging device(EIVD)for intensity-modulated radiotherapy(IMRT)of cervical cancer for investigating the differences between the measured and planned doses,and explore the optimal threshold for gamma passing rate in EIVD quality control based on dosimetric sensitivity.Methods A retrospective analysis was conducted on a cohort of 45 patients with cervical cancer who underwent IMRT at Women's Hospital,School of Medicine,Zhejiang University.During the treatment,all patients underwent EIVD to obtain the measured doses.The passing rate was analyzed using global gamma criteria of 2 mm/2%,2 mm/3%,and 3 mm/3%.Additionally,dose-volume histogram parameters were utilized to evaluate any differences between the measured and planned doses.Pearson correlation analysis was employed to investigate the relationship between the gamma passing rate and dosimetric differences.Furthermore,receiver operating characteristic(ROC)curve was generated to determine the optimal threshold for the gamma passing rate.Results The average gamma passing rates for the criteria of 2 mm/2%,2 mm/3%,and 3 mm/3%were 83.07%±5.25%,91.69%±3.52%,and 95.02%±2.46%,respectively.The Dmean deviation between EIVD measurement and planned dose in the planning target area was 2.43%(P=0.016),while the Dmean deviations in the bladder,rectum,and small intestine were 0.35%,0.46%,and 0.30%,respectively(P>0.05).Pearson analysis revealed a strong correlation between the 3 gamma indexes and dosimetric differences in the PTV(r>0.7),but a weak correlation with organs-at-risk(r<0.7).ROC analysis indicated that the optimal gamma passing rate thresholds for the criteria of 2 mm/2%,2 mm/3%,and 3 mm/3%were 79.06%,90.04%,and 94.19%,respectively.Conclusion The implementation of EIVD can ensure the accuracy of dose delivery within the PTV during IMRT for cervical cancer.Moreover,establishing a gamma passing rate threshold provides a valuable clinical basis for subsequent adaptive IMRT for cervical cancer.