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Proceedings Paper

Direct-conversion flat-panel x-ray imaging: reduction of noise by presampling filtration
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Paper Abstract

Large area flat panel solid-state detectors are being studied for digital radiography and fluoroscopy. Such systems use active matrix arrays to readout latent charge images created either by direct conversion of x-ray energy to charge in a photoconductor or indirectly using a phosphor and individual photodiodes on the active matrix array. Our work has utilized the direct conversion method because of its simplicity and the higher resolution possible due to the electrostatic collection of secondary quanta. Aliasing of noise occurs in current designs of direct detectors based on amorphous selenium ((alpha) -Se) because of its high intrinsic resolution. This aliasing leads to a decrease in detective quantum efficiency (DQE) as frequency increases. It has been predicted, using a previously developed model of the complete imaging system, that appropriately controlled spatial filtration can reduce this aliased noise and hence increase DQE at the Nyquist frequency, fNY. Our purpose is to experimentally verify this concept by implementing presampling filtration in a practical flat panel system. An (alpha) -Se based flat panel imager is modified by incorporating an insulating layer between the active matrix and the (alpha) -Se layer to introduce a predetermined amount of presampling burring. The modified imager is evaluated using standard linear analysis tools, modulation transfer function (MTF), noise power spectra (NPS) and DQE(f), and the results are compared to theoretical predictions.

Paper Details

Date Published: 25 April 2000
PDF: 10 pages
Proc. SPIE 3977, Medical Imaging 2000: Physics of Medical Imaging, (25 April 2000); doi: 10.1117/12.384519
Show Author Affiliations
John A. Rowlands, Sunnybrook & Women's College Health Sciences Ctr./Univ. of Toronto (Canada)
Winston Guangda Ji, Sunnybrook & Women's College Health Sciences Ctr./Univ. of Toronto (Canada)
Wei Zhao, SUNY/Stony Brook (United States)
Denny L. Y. Lee, Direct Radiography Corp. (United States)

Published in SPIE Proceedings Vol. 3977:
Medical Imaging 2000: Physics of Medical Imaging
James T. Dobbins; John M. Boone, Editor(s)

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