Effect of the setup error on the dosimetric verification for the volumetric modulated arc therapy / 中华放射肿瘤学杂志

ABSTRACT

Objective To evaluate the effect of the setup error on the dosimetric verification for the nasopharyngeal carcinoma patients and cervical carcinoma patients treated with volumetric modulated are therapy (VMAT).Methods VMAT plans for 10 cervical cancer patients and 10 nasopharyngeal carcinoma patients were transplanted into the Delta4 phantom and calculate the dose,next,implement the treatment on the Varian iX linear accelerator.on the Varian iX linear accelerator.To simulate the setup error by moving the treatment couch in,out,up,down,left,right by 3 mm,5 mm,7 mm.Thereby study the effect of the setup error on the pass rate of the dose verification.Results The results for the dose distribution using the gamma evaluation method showed that the pass rate (3％/3 mm) was less than 90％ when the setup error were greater than 3 mm and 5 mm for the nasopharyngeal carcinoma patients and the cervical carcinoma patients.The pass rate of head direction were (64.7 ± 8.2) ％ and (63.3 ± 3.6) ％ on setup error of 5 mm and 7 mm for nasopharyngeal carcinoma patients and cervical carcinoma patients,respectively.Conclusions Setup error has great effect on the dose verification of the VMAT plans,the greater of the setup error,the lower of the pass rate.The setup error of head direction is more sensitive than other directions especially.