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Proceedings Paper

The effect of temporal lag in back illuminated photodiodes on CT image quality
Author(s): Lothar Spies; Randy Luhta
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Paper Abstract

Image artifacts caused by a temporally delayed response of a back illuminated photodiode deployed in a CT detector were studied. The temporal response pattern, characterized by a finite rise and fall time, is an intrinsic property of a photodiode. Generally, electron-hole pairs generated in the diode take time to diffuse to contacts where they get finally registered. In the case of backilluminated diodes, diffusion time is significantly prolonged, since photons hit the diode on the back. Electrons or holes only contribute to the signal, if they travel the full distance to the frontend, where contacts are located. To study the temporal behavior of a back illuminated photodiode a computer model for a standard third generation CT scanner was devised and simulations were carried out. Resulting image artifacts were quantified for various phantom and photodiode parameters. Simulations and theory demonstrate that for a given phantom, artifacts scale with rise/fall time and the angular speed of the scanner.

Paper Details

Date Published: 20 April 2005
PDF: 10 pages
Proc. SPIE 5745, Medical Imaging 2005: Physics of Medical Imaging, (20 April 2005); doi: 10.1117/12.595077
Show Author Affiliations
Lothar Spies, Philips Research Labs. (Germany)
Randy Luhta, Philips Medical Systems (United States)

Published in SPIE Proceedings Vol. 5745:
Medical Imaging 2005: Physics of Medical Imaging
Michael J. Flynn, Editor(s)

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