Effect Of The Setup Error On The Physics Dose For Nasopharyngeal Carcinoma In The Intensity Modulated Radiation Therapy

Intensity modulated radiation therapy (IMRT) is the most advanced accurate 3D treat technique, which desires accurate irradiation body positions and veracity of portal field highly. To research the setup error and its impact in the IMRT for head-neck tumor, we choose 76 patients with head-neck tumor at random, measuring its setup error through comparing the digital portal film with digitally reconstructed radiograph (DRR) , calculating the extended margin between the clinical target volume (CTV) and planning target volume (PTV) , analyzing if the setup error has the law with the treatment time goes by. Also we choose ten nasopharyngeal carcinoma (NPC) patients among those, apply setup error into the TPS to analyze the effect resulted from dose of every targets and peripheral organ at risk (OAR) .The main research work of this subject:(1) Seventy-six patients with head-neck tumor are choosed from the resident tumor patients at random from July 2004 to September 2005. First we execute the CT orientation scan for them, and translate the images to the TPS through internet. In the TPS, the doctor sketches the target, gives prescription dose limit for target and OAR. Physics engineer sketches normal tissue, designs inverse IMRT plan, dose verification plan and position verification plan. The position verification plan includes anterior portal field and left lateral portal field. Every field is set bone window and soft tissue window separately to get anterior and lateral (DRR) .(2) After doctor's verification, IMRT plan, dose verification plan and position verification plan are transferred to the image workstation and accelerator workstation. After dose verification plan is passed, we get the position verification through net before treat, the portal films are screened using the electronic portal imaging device (EPID) .(3) Every patient's DRR and electronic portal images are saved in the image workstation, we get 3D setup error through comparing two groups with each other by image analysis software. Deal with all the patients' error data by...