Electronic portal imaging device (EPID) based on a novel camera with avalanche multiplication

Electronic portal imaging devices (EPIDs) have many potential advantages over portal films used in radiation therapy. The most commonly used EPIDs are video-based systems. Camera noise is one of the main noise sources which limit the performance of current video-based EPIDs. In this paper, we investigate the use of an avalanche-multiplication-based video camera to effectively eliminate the camera noise in an EPID and, therefore, to improve the quality of megavoltage portal images. To make these investigations, a new EPID with the avalanche-multiplication-based video camera has been made. Detective quantum efficiency (DQE) of the new device has been measured with a ⁶⁰Co radiation beam. It is shown that the camera noise is much smaller than the quantum noise in the new EPID system and the DQE value of the system is significantly increased because of the elimination of camera noise.