THIN-FILM, FLAT-PANEL, COMPOSITE IMAGERS FOR PROJECTION AND TOMOGRAPHIC IMAGING

The recent development of large-area, flat-panel a-Si:H imaging arrays is generally expected to lead to real-time diagnostic and megavoltage x-rav projection imagers with film-cassette-like profiles. While such flat-panel imagers offer numerous advantages over existing fluoroscop ic and radiographic imaging devices, the unique properties of the arra ys also offer the prospect of detector configurations not previously p ossible with other real-time technologies. The thin, highly uniform pr ofile of the arrays allows the creation of composite imaging devices i n which a flat-panel detector overlies a second imaging detector. A du al-energy (diagnostic and megavoltage) composite imager consisting of a pair of stacked, flat-panel imagers would provide unique information helping to resolve the patient localization and verification problem in megavoltage radiotherapy. In PET or SPECT, attenuation corrections could be obtained by placing a flat-panel array for transmission measu rements directly in front of the main emission detector. In this artic le, the concept of such real-time flat-panel composite imagers is prop osed. Specific embodiments of this concept applied toward the resoluti on of outstanding problems in radiotherapy, PET and SPECT are outlined and calculations and data supporting the feasibility of the concept a re presented.