Evaluation of positional accuracy of EPID using IMRT graticule phantom in extended source to imager distance setups: formalism of QA

In this modern era of Radiotherapy the Imaging technology now plays very important role in the delivery of radiation with accuracy up to the order of millimeter. Therefore, their performance should also be evaluated in different patient settings especially in nonstandard. The aim of the present study was to evaluate the utility of IMRT graticule phantom to check the positional accuracy of EPID (amorphous silicon flat panel detector, retractable arm) and to develop a quality assurance program for geometrical verification