HIGH RESOLUTION CARDIOVASCULAR FLAT-PANEL X-RAY IMAGER

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Recent advances in cardiovascular imaging have contributed to the development of new, widely used lifesaving x-ray interventional procedures. This has prompted concerns about the radiation dose- efficiency of present equipment and techniques. When the equipment is not capable of delivering excellent image quality for visualizing subtle or small vasculature required for challenging diagnostic or therapeutic interventional procedures, physicians have little choice but to prolong fluoroscopy or acquire more cine views. This research is aimed at designing, developing and evaluating a new type of high resolution imaging device for cardiac x-ray fluoroscopy and cine imaging. This effort follows the successful research conducted by our group in the past four years to adapt charge-coupled device (CCD) technology to digital mammographic imaging applications. The device will be a CCD-based flat panel detector consisting of four 8 cm x 8 cm CCDs joined in a seamless design to form an area of 16 cm x 16 cm (6.3 x 6.3 inch, 8.9 inch diagonal). The design takes advantage of the low-noise characteristics for which CCDs are known, with a new interline charge transfer design for 30 frame/s or even 60 frames/s fluoroscopic video. The proposed detector and technique circumvents problems due to image lag (smearing), associated with other types of flat panel detectors and is radically different from any other detector of its kind. As far as we know, large scientific grade CCDs have never been developed to operate in the interline transfer mode for video frame rate imaging for x-ray fluoroscopy or any other application. Our system will be x-ray quantum-noise limited and unlike image intensifier systems, it will be free of geometric distortion and veiling glare effects which cause significant loss of contrast. The new system will be able to deliver better detective quantum efficiency (DQE) and spatial resolution in both fluoroscopic and radiographic modes than existing image intensifier-based systems. The improved contrast characteristics would enable better visualization of cardiovascular anatomy and functionality at a reduced radiation dose to the patient. The research will involve the design and manufacturing of the CCD which will be followed by comprehensive adaptation of the device to the fluoroscopic and radiographic tasks. Investigation of the imaging characteristics of the detection system will be conducted through objective and universally accepted metrics such as modulation transfer function (MTF) and frequency dependent detective quantum efficiency (DQE).