Megavoltage X-Ray Imaging Detector Based on Cerenkov Effect

A Monte Carlo simulation was used to study imaging and dosimetric characteristics of a novel design of a megavoltage (MV) x‐ray imaging detector. The proposed detector consists of a matrix of optical fibers aligned with the incident x‐rays and coupled to an active matrix flat‐panel imager (AMFPI) for image readout. The new design relies on Cerenkov effect for MV x‐ray imaging and is named CPID (for Cerenkov Portal Imaging Device). When MV x‐rays are incident on CPID, they interact within the volume of the detector primarily via Compton effect and pair‐production, resulting in electrons and positrons. From these charged particles, those with sufficient energy, trigger production of optical light via Cerenkov effect. The light that is generated in the optical fibre cores within the acceptance angle of the fibers is guided towards the AMFPI. Properties, such as detection efficiency, modulation transfer function, zero frequency detective quantum efficiency (DQE), and energy response of the detector, have been investigated. It has been shown that the proposed detector can have a zero‐frequency DQE more than an order of magnitude higher than that of current electronic portal imaging device (EPID) systems and yet a spatial resolution comparable to that of video‐based EPIDs. In additional the proposed detector is less sensitive to scattered x‐rays than current EPIDs. © 2012, American Association of Physicists in Medicine. All rights reserved.