ABSTRACT
Electronic portal imaging devices (EPIDs) have been developed for verification of patient positioning prior to or during the treatment delivery. Since the introduction of the amorphous silicon-based EPIDs, almost every linac is equipped with an EPID panel. Due to its favorable dosimetric characteristics such as high resolution, fast imaging acquisition, and digital format, EPIDs have been used for radiation therapy dose measurements for more than two decades. It has broad dosimetry applications for both patient-specific intensity-modulated radiation therapy/volumetric-modulated arc therapy (IMRT/VMAT) quality assurance (QA) including pre-treatment and in vivo patient treatment verification and linac machine QA. It can be used to verify almost every aspect of machine performance. In this chapter, we will provide a review of EPIDs dosimetric characteristics and application to both patient-specific and linac QA.
