Dosimetric characterization of an electronic portal imaging device (EPID) and development of a portal dosimetry simple model

The use of the Electronic Portal Imaging Devices (EPID) for the quality control of linear accelerators of electrons is increasingly extended in practice. In this work the dosimetric characteristics of an EPID OptiVue 1000 ST were studied and a friendly and simple method for the absorbed dose calibration was suggested. This method is based on a simple mathematical model, including: an absorbed dose transformation coefficient and image lag and field shape corrections. Software tools were developed in order to process the information and the results were validated by comparing them with the measured data with ionization chambers. The studied device showed suitable characteristics for its use for EPID dosimetry and the calculated results fitted satisfactorily with the dose planes obtained with the ionization chambers. Keeping in mind the model limitations, we concluded that it is possible to start the use of the EPID for the accelerator quality control and improvements for the current model should be studied, as well as other suitable applications: e.g. the Intensity Modulated Radiation Therapy (IMRT) treatment verification procedures. (Author).