ABSTRACT
Evaluating electronic portal imaging device (EPID) detector design alternatives and understanding its performance for imaging and dosimetry applications is enhanced by having a detailed understanding of how the EPID responds as a radiation detector. A primary tool for evaluating expected detector response and performance is Monte Carlo (MC) radiation transport simulations. EPID MC simulations are typically used to understand detector response; predict images either with or without the patient; and compute energy-deposition kernels to aid alternative calculation algorithms. For accurate response simulation, the geometric model for an EPID MC simulation should be based on the manufacturer design specifications. For the MC, the geometric model consists of multiple parallel planes of uniform materials. Although flat-panel imagers yield a signal when operated in direct measurement mode without an intensifying screen, intensifying screens are used to increase sensitivity in all commercial EPIDs. For pretreatment and patient-EPID image calculations, accuracy is limited by the accuracy of the source model used in the calculations.
