title: Electronic portal imaging with an avalanche-multiplication-based video camera.
abstract: The aim of this study is to investigate the degree to which the imaging quality of an existing (video-based) electronic portal imaging device (EPID) system may be improved by using an avalanche-multiplication-based video camera (called the avalanche-gain method). Due to avalanche multiplication in the target of the video camera tube, the new camera can be made up to several hundred times more sensitive than a camera using a conventional video (e.g., Saticon) tube. As a result, the camera noise which limits the performance of current video-based EPIDs should be overwhelmed and made negligible. The detective quantum efficiency (DQE) of an EPID using the avalanche-gain method has been measured with 6 MV and 18 MV beams obtained using a linear accelerator. It is shown that the camera noise is indeed much smaller than quantum noise and that the DQE of the system is significantly increased compared to conventional video-based EPIDs. Variation of DQE of the avalanche-gain video portal system with a change of demagnification was also investigated. It has been shown that the improvement of optical coupling has less effect in this system than that in a conventional video-based EPID system.
authors.affiliation: Toronto-Sunnybrook Regional Cancer Center, Department of Radiation Oncology, University of Toronto, Canada. pang@phoebus.sunnybrook.utoronto.ca
authors.forename: G
authors.initials: G
authors.lastname: Pang
authors.forename: J A
authors.initials: JA
authors.lastname: Rowlands
mesh_terms: D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation* / Q000379:methods*; D008027:Light; D015233:Models, Statistical; D010315:Particle Accelerators / Q000295:instrumentation; D011789:Quantum Theory; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation* / Q000379:methods*; D012680:Sensitivity and Specificity; D014741:Video Recording / Q000379:methods; D014965:X-Rays