The Application Research Of EPID In Dose Verification

Radiation therapy is one of the most effective and common means of treating tumors.At present,the most important radiotherapy technologies are IMRT and VMAT with high accuracy and complexity.More rigorous and accurate quality control is needed to ensure the effectiveness of treatment,and the pre-treatment planned dose validation is one of the essential items in quality control content.The amorphous silicon electronic portal imaging device(a-Si EPID)has many advantages such as easy to use,high dose imaging speed,no angle response and high resolution.So,this study focuses on the application of EPID used in dose verification based on the portal dosimetry(PD)verification tool.Ideas and methods: EPID is compared with several widely accepted and commonly used as dose verification tools to check their equivalence and substitution for each other.Two groups of contrast experiments are designed in this study,IMRT group and VMAT group,each group selected nasal cancer,cervical cancer,rectal cancer cases,40 cases in each cancer and a total of 120 cases.Dosimetry was performed on the IMRT plan using EPID and PTW.The results were compared for the absolute dose rate and the relative dose rate.The VMAT plans were validated by EPID and Arc CHECK,and the validation results were also for comparison analysis.The paired t test and Spearman rank correlation analysis method are used to verify the results and the relevance and consistency were judged for dose verification results of EPID to PTW and Arc CHECK.Results: In the IMRT group,the γpassing rates of absolute dose and relative dose of EPID are 97.64%±1.19% and 98.21%±1.12%,respectively.The γpassing rates of absolute dose and relative dose of PTW are 97.59%±1.25% and 98.19%±1.07%,respectively.With the paired t check,p=0.545 for the γpassing rates of absolute dose for EPID and PTW,and p=0.707 for the γpassing rates of relative dose for EPID and PTW.With the Spearman rank correlation analysis,ρ=0.615 for the γpassing rates of absolute dose for EPID and PTW,and ρ=0.519 for the γpassing rates of relative dose for EPID and PTW.In the VMAT group,the γpassing rates of absolute dose and relative dose of EPID are 97.54%±1.22% and 98.13%±1.22%,respectively.The γpassing rates of absolute dose and relative dose of Arc CHECK are 97.47%±1.10% and 98.18%±1.17%,respectively.With the paired t check,p=0.301 for the γpassing rates of absolute dose for EPID and Arc CHECK,and p=0.306 for the γpassing rates of relative dose for EPID and Arc CHECK.With the Spearman rank correlation analysis,ρ=0.676 for the γpassing rates of absolute dose for EPID and Arc CHECK,and ρ=0.567 for the γ passing rates of relative dose for EPID and Arc CHECK.Conclusions: EPID is relevant and consistent to PTW and Arc CHECK in the pass rate of dose validation.So,EPID can be used as an effective and convenient tool for dose verification to ensure the accuracy of radiation therapy.