ABSTRACT
Over the past decade, image-guided radiation therapy (IGRT) has become an essential component of contemporary clinical practice. High-quality beam's eye view (BEV) imaging can, in principle, be achieved using either the megavoltage (MV) treatment beam or a separate in-line kilovoltage (kV) X-ray system. Nearly all commercial electronic portal imaging devices (EPIDs) use an indirect detection mechanism. The ability to perform high-quality BEV imaging introduces several intriguing possibilities for enhancing IGRT. The main design parameters affecting performance are the scintillator material's density and atomic number, the pixel geometry (size, aspect ratio, and fill factor), and the optical properties of the scintillator (scintillation yield, clarity, and index of refraction). It also includes the scintillator finishing processes (polishing, and grinding), the reflector properties (reflectivity and transmissivity coefficients, type of reflection—specular or lambertian), the effects of beam divergence, and the number of imaging layers.
