The Effect Of The Set Up Error On The Dosimetric Verification For Intensity Modulated Radiation Therapy(IMRT) Based On The Arc Check Phantom

radiation therapy is one of the main method treating malignant tumor. Data show that nearly two-thirds of the cancer patients need to accept different levels of radiation therapy. The application of radiation therapy can relieve the suffering of the cancer patients and improve the 5-year survival rate. However, the setup error can affect dose distribution and the pass rate of dosimetric verification.To evaluate the effect of the Set up error on the dosimetric verification for intensity modulated radiation therapy(IMRT) based on Arc Check phantom. IMRT plans for 20 nasopharyngeal carcinoma patients、20 breast cancer patients、20 lung cancer patients and 20 cervical cancer patients were transplanted into Arc Check phantom and calculate the dose, next,implement the treatment on the varian true BEAM accelerator. To simulate the error by moving treatment dose map rotation by ±0.5 degree,±1.0 degree,±1.5 degree,±2.0degree and translation by ±1mm, ±3mm, ±5mm, ±7mm.Thereby study the effect of rotation and translation setup error on the pass rate of the dose verification. The results can provide reference for clinical placement. The results for the dosedistribution using the gamma evaluation method showed that the pass rate(3%/3 rain) of relative dose Was(98.06±2.025)%、(98.32±2.02)%、(99.26±1.20)%、(99.33±0.64)% for the nasopharyngeal carcinoma patients 、breast cancer patient、lung cancer patient and the cervical carcinoma patients,respectively.The results for the dose distribution using the gamma evaluation method showed that the pass rate(3%/3 rain) of absolute dose Was(97.97±2.06)%、(98.16±1.20)%、(98.09±2.54)%、(98.93±0.94)% for the nasopharyngeal carcinoma patients 、breast cancer patient、lung cancer patient and the cervical carcinoma patients,respectively.The pass rate of cancer were less than 95%,when the rotation setup error were greater than 0.5 degree or the translation set up error great than 3mm of5 mm and 7 mm the nasopharyngeal carcinoma patients 、breast cancer patient、lung cancer patient and the cervical carcinoma patients. The Setup error has great effect on the dose verification of the IMRT plans,the greater of the setup error,the lower of the pass rate.We should pay attention to the setup error affecting the efficacy of radiotherapy.