<title>Large area mercuric iodide thick film x-ray detectors for fluoroscopic (on-line) imaging</title>

Abstract

Polycrystalline Mercuric Iodide coated TFT arrays are now the best candidates for direct digital radiographic detectors for both static and dynamic (fluoroscopic) applications. Their high X-ray sensitivity, high resolution, low dark current, low voltage operation, and good lag characteristics meet the required imaging performance parameters. Small area (2'x2') mercuric iodide x-ray detectors were already reported to have good resolution and high x-ray sensitivity. The present paper reports results obtained with good quality large active area (4'x4') HgI2 imagers deposited on an a-Si TFT matrix containing 768 x 768 pixels with pitch dimensions of 139 micrometers . Coating thickness of the HgI<SUB>2</SUB> is between 150 micrometers and 250 micrometers and the imagers were tested in the 25 kVp-100 kVp x-ray energy range utilizing exposures typical for both fluoroscopic and radiographic imaging. The resolution of the imagers is practically limited only by the pixel size (139micrometers ). The imager works at 15 Hz fluoro rate and the image lag is very small. The imager can use exceptionally low dose-rate x-ray illumination because of the very high x-ray sensitivity, which exceeds any other known X-ray imager materials. The paper also discusses potential application fields of this new unique imager.