Share Email Print
cover

Proceedings Paper

Detailed imager evaluation and unique applications of a new 20x25-cm size mercuric iodide thick film x-ray detector
Author(s): George Zentai; Larry D. Partain; Raisa Pavlyuchkova; Cesar Proano; Gary F. Virshup; Barry N. Breen; Alexander I. Vilensky; Ofer Dagan; E. Meerson; M. Schieber; Haim Gilboa; Jerry A. Thomas
Format Member Price Non-Member Price
PDF $14.40 $18.00

Paper Abstract

We previously reported on 2"x 2" and 4" x 4" size imagers, direct digital radiography X-ray detectors, based on photoconductive polycrystalline mercuric iodide deposited on a flat panel thin film transistor (TFT) array, as having great potential for use in medical imaging, NDE, and security applications. Recently we successfully upgraded our mercuric iodide deposition technique to 20 cm x 25 cm size, the size required in common NDE and security imaging applications. A TFT array with a pixel pitch of 127 microns was used for this imager. The mercuric iodide direct conversion layers were vacuum deposited onto TFT array by Physical Vapor Deposition (PVD). In addition to successful imager scale up, more sophisticated, non-TFT based detectors were developed in order to improve analysis methods of the mercuric iodide photoconductor. Measurements on mercuric iodide photoconductor were performed using a 36 x 6 electrode array on a 10cm x 10cm substrate (total of 216 measurement points). The array is formed by 36 palladium stripes on the glass substrate, upon which the mercuric iodide is deposited, and 6 palladium stripes that are deposited on top of the mercuric iodide layer. These two sets of electrodes are oriented at 90 degrees to each other to create the measurement matrix. These detectors were evaluated in radiographic mode, continuous fluoroscopic mode and pulsed fluoroscopic mode. Mercuric iodide coatings with thickness ranging between 140 microns and 300 microns were tested using beams with energies between 40 kVp and 100 kVp utilizing exposure ranges typical for both fluoroscopic and radiographic imaging. Diagnostic quality radiographic and fluroscopic images at up to 15 pulses per second were demonstrated. We evaluated the dark current, sensitivity and MTF characteristics. The MTF is determined primarily by the aperture and pitch of the TFT array with Nyquist frequency of ~3.93 mm-1 (127 micron pixel pitch). The MTF curve of a good quality HgI2 imager is very close to the theoretical sinc function. Image lag characteristics of mercuric iodide appear adequate for fluoroscopic rates.

Paper Details

Date Published: 1 August 2003
PDF: 12 pages
Proc. SPIE 5047, Smart Nondestructive Evaluation and Health Monitoring of Structural and Biological Systems II, (1 August 2003); doi: 10.1117/12.484035
Show Author Affiliations
George Zentai, Varian Medical Systems, Inc. (United States)
Larry D. Partain, Varian Medical Systems, Inc. (United States)
Raisa Pavlyuchkova, Varian Medical Systems, Inc. (United States)
Cesar Proano, Varian Medical Systems, Inc. (United States)
Gary F. Virshup, Varian Medical Systems, Inc. (United States)
Barry N. Breen, Real Time Radiography Readout (Israel)
Alexander I. Vilensky, Real Time Radiography Readout (Israel)
Ofer Dagan, Real Time Radiography Readout (Israel)
E. Meerson, Real Time Radiography Readout (Israel)
M. Schieber, Real Time Radiography Readout (Israel)
Haim Gilboa, Real Time Radiography Readout (Israel)
Jerry A. Thomas, Uniformed Services Univ. of the Health Sciences (United States)


Published in SPIE Proceedings Vol. 5047:
Smart Nondestructive Evaluation and Health Monitoring of Structural and Biological Systems II
Tribikram Kundu, Editor(s)

© SPIE. Terms of Use
Back to Top