The goal of developing an on -line electronic digital radiographic (EDR) system to replace conventional film-screen radiography (FSR) is important for at least two reasons. First, theoretical arguments show that EDR can have improved diagnostic quality, reduced patient dose and faster image accessibility than FSR.Secondly, the availability of EDR systems will remove the final impediment to the realization of the PACS concept inasmuch as FSR is the only major nonelectronic imaging modality left in the modern radiology department.The Kinestatic Charge Detector (KCD) has properties which make it a candidate for an on -line EDR systems -10.The KCD is a strip detector with high spatial resolution in two dimensions. However, mechanically and electronically, it operates like a one -dimensional detector.Thus, it can effectively scan on the order of 64 to 128 parallel x -ray lines simultaneously but with a 64 to 128 -fold reduction in the number of actual detector cells and electronic channels.Moreover, this can be done at quantum detection efficiencies approaching unity.In this paper, theoretical calculations and experimental measurements of the performance parameters of a KCD are presented. Some of the particular parameters discussed include spatial, contrast, and temporal resolution.
Strip (or slot) beam digital radiography has been proposed as an ideal compromise between the excellent scatter rejection of pencil -beam or single -line scanned projection radiography systems and the excellent x -ray utilization of wide area beam systems. Moreover, the Kinestatic Charge Detector (KCD) has been proposed as a strip beam detector candidate with a potential for achieving a spatial resolution of over 5 cy /mm, a quantum detection efficiency (QDE) near unity ( > 90 %) and a local exposure time at a given contrast resolution which is less than other detection techniques (i.e., reduced motion blurring).Several laboratory KCDs containing various numbers of channels have now been constructed and tested which allow a better understanding of the practical performance which can be expected from a strip beam digital radiography system using a KCD.Improved theoretical estimates of the performance of a KCD are presented using (1) an ion transport simulator incorporating a numerical solution for the three -dimensional electric-fields in the KCD and (2) an x -ray Monte Carlo program which was recently modified to include the form factors for coherent and Compton scattering as well as to include L -shell photoelectric interactions.The ion transport simulator allows one to study both ion transmission efficiency and ion arrival time distributions.Using the Monte Carlo program, improved estimates are obtained of patient scatter acceptance, in-detector scattering and detective quantum efficiency (DQE).Improved measurements of spatial resolution are presented as well.
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