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Performance characteristics of a real‐time digital x‐ray fluoroscopic system using an intensified charge injection device camera and CsI:Na crystal
Author(s) -
Atari Nader A.
Publication year - 1989
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.596312
Subject(s) - optical transfer function , optics , scintillator , charge coupled device , image resolution , frame rate , physics , digital radiography , computed radiography , detective quantum efficiency , full width at half maximum , image sensor , materials science , phosphor , image quality , radiography , optoelectronics , detector , computer science , artificial intelligence , nuclear physics , image (mathematics)
A digital x‐ray photoelectronic imaging system has been constructed using an optically flat 152‐mm‐diam, 2.5‐mm‐thick CsI:Na scintillating crystal. X‐ray images formed by the scintillator are viewed by a single microchannel plate intensified charge injection device (ICID) camera and digitized at a real‐time rate by a computerized frame‐grabbing system. Video images are recorded and selected image frames are subjected to image processing and analysis schemes. Parameters governing the performance characteristics of the system are determined accordingly. For a 152‐mm field size at the crystal plane, a spatial resolution limit of 1.50±0.10 1p/mm (1σ) measured at the 4% level of the modulation transfer function of the system has been obtained. This result is consistent with the measurements of the full width at half‐maximum of the line spread function which is found to be 645±35 μm (1σ). Similarly, the intrinsic resolution of the CsI:Na scintillator only was found to be 6.5±0.5 1p/mm (1σ). Contrast ratio measurements, which are mainly determined by the quality of phosphor, have indicated a value of 12.1±0.6, whereas minimum visible details are observed at radiation exposure rates of 100 μR/s. This limit has been reduced to 10 μR/s using the single‐scan integrating option provided by the ICID camera. A maximum contrast resolution of 1% corresponding to 100 statistically significant meaningful gray levels is achieved at a maximum exposure rate of 1000 μR/s. Consequently, although the imaging capability of the present system compares favorably with that of conventional x‐ray video‐fluoroscopic systems, a better performance may be achieved by using a higher resolution cooled dual‐microchannel intensified CID camera in conjunction with a thinner CsI:Na crystal and a real‐time digital image processing subsystem.