title: Electronic portal imaging devices: a review and historical perspective of contemporary technologies and research.
abstract: A review of electronic portal imaging devices (EPIDs) used in external beam, megavoltage radiation therapy is presented. The review consists of a brief introduction to the definition, role and clinical significance of portal imaging, along with a discussion of radiotherapy film systems and the motivations for EPIDs. This is followed by a summary of the challenges and constraints inherent to portal imaging along with a concise, historical review of the technologies that have been explored and developed. The paper then examines, in greater depth, the two first-generation technologies that have found widespread clinical use starting from the late 1980s. This is followed by a broad overview of the physics, operation, properties and advantages of active matrix, flat-panel, megavoltage imagers, presently being commercially introduced to clinical environments or expected to be introduced in the future. Finally, a survey of contemporary research efforts focused on improving portal imaging performance by addressing various weaknesses in existing commercial systems is presented.
authors.affiliation: Department of Radiation Oncology, University of Michigan, Ann Arbor 48109-0010, USA. antonuk@umich.edu
authors.forename: Larry E
authors.initials: LE
authors.lastname: Antonuk
mesh_terms: D049673:History, 20th Century; D006801:Humans; D010315:Particle Accelerators; D017785:Photons; D011859:Radiography / Q000266:history / Q000295:instrumentation / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D013679:Technology, Radiologic