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Proceedings Paper

Simulation study of an energy sensitive photon counting silicon strip detector for computed tomography: identifying strengths and weaknesses and developing work-arounds
Author(s): Hans Bornefalk; Cheng Xu; Christer Svensson; Mats Danielsson
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Paper Abstract

We model the effect of signal pile-up on the energy resolution of a photon counting silicon detector designed for high flux spectral CT with sub-millimeter pixel size. Various design parameters, such as bias voltage, lower threshold level for discarding of electronic noise and the entire electronic read out chain are modeled and realistic parameter settings are determined. We explicitly model the currents induced on the collection electrodes of a pixel and superimpose signals emanating from events in neighboring pixels, either due to charge sharing or signals induced during charge collection. Electronic noise is added to the pulse train before feeding it through a model of the read out electronics where the pulse height spectrum is saved to yield the detector energy response function. The main result of this study is that a lower threshold of 5 keV and a rather long time constant of the shaping filter (τ0 = 30 ns) are needed to discard induced pulses from events in neighboring pixels. These induction currents occur even if no charge is being deposited in the analyzed pixel from the event in the neighboring pixel. There is also only a limited gain in energy resolution by increasing the bias voltage to 1000 V from 600 V. We show that with these settings the resulting energy resolution, as measured by the FWHM/E of the photo peak, is 5% at 70 keV.

Paper Details

Date Published: 22 March 2010
PDF: 11 pages
Proc. SPIE 7622, Medical Imaging 2010: Physics of Medical Imaging, 76223P (22 March 2010); doi: 10.1117/12.843914
Show Author Affiliations
Hans Bornefalk, Royal Institute of Technology (Sweden)
Cheng Xu, Royal Institute of Technology (Sweden)
Christer Svensson, Linköping Univ. (Sweden)
Mats Danielsson, Royal Institute of Technology (Sweden)

Published in SPIE Proceedings Vol. 7622:
Medical Imaging 2010: Physics of Medical Imaging
Ehsan Samei; Norbert J. Pelc, Editor(s)

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