الفهرس 
AcknowledgmentOnly 14 pages are availabe for public view
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Abstract
Electronic portal imaging devices (EPIDs) are available for clinical use not only to replace film, but it has been shown to be an important tool for setup error assessment and quantification of motion during treatment, treatment technique Quality Assurance (QA) and treatment machine QA. In the case of multi-image, intrafractional assessment, or quantitative analysis of 3D treatment setup parameters, EPID is the only method to perform the task. The improvement in treatment outcome anticipated with Three Dimensional Conformal Radiation Therapy (3-DCRT) as well as with Intensity Modulated Radiation Therapy (IMRT). Nowadays, EPIDs can be successfully implemented in the clinic. The treatment team must establish specific goals for use and an understanding of the process as it pertains to their clinical practice. Through answering the questions and making commitments, the EPID will prove to be much more than a simple film replacement This study included twenty patients with head and neck tumors.According to the previous words, we aimed to1-Extract quantitative data from direct measurements of interfraction variability of patient’s setup.2-Assess the impact of:<a)- Simulation technique.(b)- Immobilization variability c)- Surgical intervention on inter- and intrafractional variations of individual and population-based CTV-to-PTV margins.3- Evaluate the variation in dose using Tow Dimensional Ionization Chamber Array (2D-Array).