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Proceedings Paper

New developments in full-field radiography detectors: Direct conversion selenium detector with avalanche gain layer
Author(s): Denny L.Y. Lee; George Storti; Kelly P. Golden
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Paper Abstract

Amorphous selenium direct-conversion x-ray detectors have been used successfully for full field digital mammography (FFDM) and digital radiography (DR). Such detectors characteristically exhibit high spatial resolution and conversion efficiency that is a function of the applied electric field. About 50 electron volts of photon energy are required to generate each electron-hole pair in a typical amorphous selenium x-ray conversion layer biased at 10 volts per micron. At FFDM and DR imaging x-ray energies each absorbed photon can generate only about 250 to 1000 electron-hole pairs. Medical imaging applications must therefore employ low noise thin film transistor (TFT) arrays and charge integration amplifiers to achieve high signal-to-noise ratio (SNR) and detective quantum efficiency (DQE). To assure quantum-noise limited imaging results with the lowest practical x-ray exposure dose, it is desirable to include an additional low-noise gain stage in the x-ray conversion layer. We have proposed and studied a new structure for an amorphous selenium detector that employs an internal biased gain grid to cause avalanche-gain within the x-ray conversion layer. An amplification of at least 10X can be achieved without introducing excessive noise. Quantum-limited image detection should then be attainable for even very low exposures.

Paper Details

Date Published: 26 October 2004
PDF: 7 pages
Proc. SPIE 5541, Penetrating Radiation Systems and Applications VI, (26 October 2004); doi: 10.1117/12.565869
Show Author Affiliations
Denny L.Y. Lee, Direct Radiography Corp. (United States)
George Storti, Direct Radiography Corp. (United States)
Kelly P. Golden, Direct Radiography Corp. (United States)

Published in SPIE Proceedings Vol. 5541:
Penetrating Radiation Systems and Applications VI
F. Patrick Doty; Richard C. Schirato; H. Bradford Barber; Hans Roehrig, Editor(s)

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