title: Detective quantum efficiency of a direct-detection active matrix flat panel imager at megavoltage energies.
abstract: The use of an amorphous selenium (a-Se) based direct-detection active matrix flat-panel imager (AMFPI) is studied for megavoltage imaging. The detector consists of a 1.2 mm copper front plate and 200 microm a-Se layer, and has a 85 microm pixel pitch. The Modulation Transfer Function (MTF), Noise Power Spectrum (NPS), and Detective Quantum Efficiency (DQE) are measured for 6 and 15 MV photon beams. A theoretical expression for the DQE is derived using a recently developed formalism for nonelementary cascade stages. A comparison of theory with experiment is good for the 6 and 15 MV beams. The model is used to explore the DQE for more typical pixel sizes. The results indicate that with proper modifications, such as a larger a-Se thickness, a direct flat-panel AMFPI is a very promising detector for megavoltage imaging.
authors.affiliation: Cross Cancer Institute and University of Alberta, Edmonton, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Lachaine
authors.forename: E
authors.initials: E
authors.lastname: Fourkal
authors.forename: B G
authors.initials: BG
authors.lastname: Fallone
mesh_terms: D004583:Electrons; D007090:Image Interpretation, Computer-Assisted / Q000295:instrumentation* / Q000379:methods*; D008962:Models, Theoretical; D009010:Monte Carlo Method; D017785:Photons; D011789:Quantum Theory; D012643:Selenium
chemical_list: D012643:Selenium