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Proceedings Paper

Flat panel detector for digital radiology using active matrix readout of amorphous selenium
Author(s): John A. Rowlands; Wei Zhao; Ira M. Blevis; Gendi Pang; Winston Guangda Ji; Stephen Germann; Safa O. Kasap; David F. Waechter; Zhong Shou Huang
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Paper Abstract

A large area, flat panel solid state detector is being investigated for both digital radiography and fluoroscopy. The detector employs amorphous selenium (a-Se) to detect x- rays. The charge image formed on the surface of the a-Se is read out in situ using an active matrix array. A theoretical analysis of the spatial frequency dependent detective quantum efficiency (DQE) is performed. Because of the very high intrinsic resolution of a-Se, the detector is inherently undersampled and aliasing is always present. An interpretation of DQE(f) for the undersampled a-Se detector will be given. The analysis shows that the main factors, besides the quantum efficiency of the a-Se layer, affecting DQE(f) are: (1) aliasing; (2) gain fluctuation noise of a- Se, i.e., the Swank factor of a-Se; (3) electronic noise which prevents quantum noise limited operation at low exposure levels such as those used in fluoroscopy and (4) temporal response which causes a reduction in noise by averaging. The validity of the theoretical model was confirmed experimentally using our prototype detector with the Swank factor being established using pulse height spectroscopy. The model was then applied to three important x-ray imaging applications: mammography, chest radiography and fluoroscopy. The results show that the most important strategy for maximizing DQE(f) is to increase the pixel fill factor which can be unity using specialized techniques Methods for reducing aliasing in the detector will be described.

Paper Details

Date Published: 2 May 1997
PDF: 12 pages
Proc. SPIE 3032, Medical Imaging 1997: Physics of Medical Imaging, (2 May 1997); doi: 10.1117/12.273974
Show Author Affiliations
John A. Rowlands, Sunnybrook Health Science Ctr./Univ. of Toronto (Canada)
Wei Zhao, Sunnybrook Health Science Ctr./Univ. of Toronto (Canada)
Ira M. Blevis, Sunnybrook Health Science Ctr./Univ. of Toronto (Canada)
Gendi Pang, Sunnybrook Health Science Ctr./Univ. of Toronto (Canada)
Winston Guangda Ji, Sunnybrook Health Science Ctr./Univ. of Toronto (Canada)
Stephen Germann, Sunnybrook Health Science Ctr./Univ. of Toronto (Canada)
Safa O. Kasap, Univ. of Saskatchewan (Canada)
David F. Waechter, Litton Systems Canada, Ltd. (Canada)
Zhong Shou Huang, Litton Systems Canada, Ltd. (Canada)


Published in SPIE Proceedings Vol. 3032:
Medical Imaging 1997: Physics of Medical Imaging
Richard L. Van Metter; Jacob Beutel, Editor(s)

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