基于EPID在体三维剂量验证系统的物理模型测试及初步临床探索

Preliminary study of physical model test and clinical application based on EPID-based in-vivo dose verification system

目的使用模体验证基于电子射野影像装置(EPID)在体三维剂量验证建模的准确性,并进行临床应用的初步研究。方法通过方野和调强计划在均匀和非均匀模体上检测EPID在体三维剂量验证系统应用于不同介质中的剂量计算精度和重建精度,比较不同剂量/距离一致性标准下的γ通过率。对临床病例进行靶区和危及器官剂量体积分析。结果方野在均匀模体中3%/3 mm标准平均γ通过率为(97.49±1.11)%,在非均匀模体中为(94.06±5.11)%(P>0.05)。不同出束方式的调强计划之间也相近(P>0.05)。临床病例疗前剂量验证3%/2 mm标准γ通过率为(97.96±1.84)%,在体三维剂量验证3%/3 mm标准为(90.51±6.96)%。临床病例中小体积和体积变化较大的危及器官有较大剂量偏差。结论基于EPID建立的在体三维剂量验证模型,经初步测试可应用于临床提供更全面的质量保证,为以后自适应放疗工作提供了技术保障。

Objective To validate the accuracy of physical model of in-vivo 3D dose verification based on electronic portal imaging device(EPID)using the phantom and preliminarily analyze the clinical application.Methods Two phantoms(uniform and non-uniform phantoms)were involved in this study.The system of in-vivo 3D dose verification based on EPID was employed to acquire the images of square fields(SF)and combined fields of intensity-modulated radiotherapy(CFIMRT).The physical model of different media was constructed using the system.The factor ofγpassing rate under different dose/distance criteria was statistically compared.For clinical cases,the dose-volume histograms were adopted to analyze the dose distribution of target volume and organs at risk(OARs).Results For the SF in the uniform phantom,the averageγpassing rate(3%/3 mm)was(97.49±1.11)%,and(94.06±5.11)%for the SF in the non-uniform phantom(P>0.05).No statistical significance was noted in IMRT using different delivery methods(all P>0.05).For clinical cases,the averageγpassing rate(3%/2 mm)was(97.96±1.84)%in the pre-treatment dose verification,and(90.51±6.96)%(3%/3 mm)for the in-vivo 3D dose verification.For clinical cases,significant dose deviation was observed in OARs with small size and large volume changes.Conclusion The in-vivo 3D dose verification model based on EPID can be effectively applied in inter-fraction dose verification,providing technical support for adaptive radiotherapy in clinical practice.