Digital Fluoroscopy for Cardiac Imaging

DESCRIPTION (provided by applicant): Real-time or dynamic radiographic imaging (fluoroscopy) provides vital information concerning internal organ structure, flow of contrast agents and in-vivo instrument positioning. Fluoroscopy is a very important modality for cardiac and vascular imaging including subtraction angiography where it is used for locating and evaluating cardiac structures, major vessels, localization of major chest nodules, and presence of calcium in coronary arteries or cardiac valves. An iodine based organic compound is generally used as a contrast agent in cardio-vascular fluoroscopic imaging. Most current fluoroscopes are based upon x-ray image intensifier tube (XRII) technology. Typical specifications are a large field of view (14 inches), moderate spatial resolution (2-3 lp/mm), and operation rates up to 30 frames/sec. However, the tube's bulk is a drawback on their range of use, and add significant cost to shielding and positioning mechanical assembly. Imaging characteristics include moderate detective quantum efficiency (DQE) (<50% at zero Ip/mm and 30% at 2.5 Ip/mm), contrast ratio limited to near 40:1, and spatial resolution often degraded by vignetting and veiling glare at the output screen. Visual distortions at the tube edge are another common trait of intensifier tubes. Therefore, it can be concluded that while XRII technology provides a valuable tool, the image quality it produces leaves significant room for improvement. The goal of the proposed project is to investigate a compact, flat panel detector for real-time x-ray imaging. High sensitivity, spatial resolution, and efficiency are expected with the proposed detection system. The higher spatial resolution of the proposed system will potentially improve the ability to characterize small lesions such as athersclerotic plaque in the coronary arteries which has been one of the major goals of the National Heart, Lung & Blood Institute in recent years. Finally, the higher dynamic range of the proposed detector will provide improved image quality for small lesions near the edge of a high contrast object, a situation that occurs in cardiac studies with intravenous contrast media or when a vessel or lesion overlaps the edge of an overlying bone or a rib. The goal of the Phase I project will be demonstrate the feasibility of the proposed approach.