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Proceedings Paper

Amorphous silicon x-ray image sensor
Author(s): Jean Chabbal; Christophe Chaussat; Thierry Ducourant; Lionel Fritsch; Jean Michailos; Vincent Spinnler; Gerard Vieux; Marc Arques; Gerhard Hahm; Martin Hoheisel; Heinz Horbaschek; Reiner F. Schulz; Martin F. Spahn
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Paper Abstract

The design and the performance of a 20 cm by 20 cm flat panel x-ray detector for digital radiography and fluoroscopy is described: Thin film amorphous silicon (aSi) technology has been used to build a 1024 by 1024 photodetector matrix, each pixel including both a photodiode and a switching diode; the pixel size is 196 by 196 micrometers2. A high resolution and high absorption CsI(Tl) scintillator layer covers the top of the photodetector matrix in order to provide for x ray to light conversion. For low electronic noise and 30 fr/s operating rate we developed a custom design charge readout integrated circuit. The detector delivers a 12 bit digital output. The image quality, signal to noise ratio, and DQE are presented and discussed. The flat panel detector provides a MTF in excess of 30% at 2 lp/mm and a high contrast ratio without any distortion on the whole imaging area. The x-ray absorption is 70% for 50 KeV photons. The readout amplifier is optimized to reduce the electronic noise down to 1000 e-. This low noise level, combined with high sensitivity (1150 e-/incident x-ray quantum) provides the capability for fluoroscopic applications. The digital flat panel detector has been integrated in a C-arm system for cardiology and has been used on a regular basis in a European hospital since February 1995. The results are discussed for several operating modes: radiography and fluoroscopy. Conclusions on present detector performances, as well as further improvements, are presented.

Paper Details

Date Published: 11 April 1996
PDF: 12 pages
Proc. SPIE 2708, Medical Imaging 1996: Physics of Medical Imaging, (11 April 1996); doi: 10.1117/12.237812
Show Author Affiliations
Jean Chabbal, Thomson Tubes Electroniques (France)
Christophe Chaussat, Thomson Tubes Electroniques (France)
Thierry Ducourant, Thomson Tubes Electroniques (France)
Lionel Fritsch, Thomson Tubes Electroniques (France)
Jean Michailos, Thomson Tubes Electroniques (France)
Vincent Spinnler, Thomson Tubes Electroniques (France)
Gerard Vieux, Thomson Tubes Electroniques (France)
Marc Arques, Thomson Tubes Electroniques (France)
Gerhard Hahm, Siemens AG (Germany)
Martin Hoheisel, Siemens AG (Germany)
Heinz Horbaschek, Siemens AG (Germany)
Reiner F. Schulz, Siemens AG (Germany)
Martin F. Spahn, Siemens AG (Germany)


Published in SPIE Proceedings Vol. 2708:
Medical Imaging 1996: Physics of Medical Imaging
Richard L. Van Metter; Jacob Beutel, Editor(s)

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