Use of Amorphous Silicon (ASi) Electronic Portal Imaging Devices for Other applications for Linear Accelerator Quality Assurance

Abstract

The success of radiation therapy depends critically on the accuracy of patient alignment in treatment position day after day. Electronic portal imaging devices (EPIDs) are widely used to monitor patient position during daily radiotherapy sessions. To verify other applications for medical linear accelerator quality assurance (linac QA), images of a 10×10 cm² and 18×18 cm² open field were acquired. The EPID was positioned at a fixed detector distance of 150 cm. The wedge profile and wedge factors with high level of accuracy were demonstrated. The profiles acquired using EPID deviated in shape and magnitude by up to 16% from the ion chamber profiles. The use of EPID for linac QA could be simplified by improving the available software analysis tools, thus making it more efficient. The study showed that the EPID aSi500 has the potential to be used as a relative dosimeter, making it a very simple and efficient tool for daily QA. All EPID measurements were performed using the linear accelerator model Varian DMX. The physical characteristics measured in this work suggest that the SLIC-EPID can be an efficient tool for daily QA.