Modeling and characterization of imaging detectors for diagnostic medical digital imaging

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Flat-panel digital X-ray image sensors based on an X-ray detecting medium (either a photoconductor or a phosphor) with a self-scanned active matrix arrays provide excellent X-ray images. These image sensors capture an X-ray image electronically, and hence enable a clinical transition to digital radiography by replacing the traditional film based system. Digital imaging has tremendous implications from a clinical standpoint. Not only do they allow doctors to retrieve and inspect images quicker, they are highly portable and can be analyzed by specialists who are off-site. X-ray detectors are now commercially available for general radiography and mammography, and are under consideration for use in fluoroscopy. However, there still remain significant scientific challenges associated with dark current, image lag and ghosting, electronic noises, X-ray induced effects and long term stability of the detector. Therefore, there is much fundamental work to be done to enhance detector performance. The objectives of the proposed research are to determine the physical mechanisms causing dark current, transient photoresponse, avalanche gain and noise, X-ray induced change in detector sensitivity (ghosting) and resolution in image detectors, via detector modeling and characterization tasks. A secondary objective of this research is to investigate the material properties of X-ray photoconductors.