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Proceedings Paper

Photon counting dual energy x-ray imaging at CT count rates: measurements and implications of in-pixel charge sharing correction
Author(s): Christer Ullberg; Mattias Urech; Charlotte Eriksson; Alexander Stewart; Niclas Weber
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Paper Abstract

In photon counting detectors with small pixels, charge sharing has a significant effect on the spectral response and on the image quality. A charge can be shared between pixels for two main reasons; a photon can be physically converted at the edges or corners in-between pixels and K-edge X-ray fluorescence in the converter can redistribute radiative energy to other pixels nearby. A potential drawback of photon counting detectors is the limited count rate due to pulse pileup. Pulse-pileup also distorts the recorded energy of the X-rays as pulse pileup shifts the spectra towards higher energy. With active charge sharing correction the signals from neighboring pixels contribute to dead-time of the pixel and therefore the pulse-pileup at the same input flux is increased. We compare the measured performance of an XCounter dual energy photon counting CdTe detector with 100μm pixels with and without charge sharing correction up to an input flux of 3.5*108 photons/mm2/s and show that there is a benefit to using the charge sharing correction up to 2.5*108 photons/mm2 /s. Spectra are recorded from Am241 and Cd109 at low flux to show the energy response without pulse pileup and from a 90kVp beam at high flux. Material separation between PMMA and Aluminum is evaluated in terms of SDNR for different flux with and without charge sharing up to an input flux of 3.5*108 photons/mm2/s.

Paper Details

Date Published: 9 March 2018
PDF: 8 pages
Proc. SPIE 10573, Medical Imaging 2018: Physics of Medical Imaging, 1057319 (9 March 2018); doi: 10.1117/12.2293591
Show Author Affiliations
Christer Ullberg, XCounter AB (Sweden)
Mattias Urech, XCounter AB (Sweden)
Charlotte Eriksson, XCounter AB (Sweden)
Alexander Stewart, XCounter AB (Sweden)
Niclas Weber, XCounter AB (Sweden)

Published in SPIE Proceedings Vol. 10573:
Medical Imaging 2018: Physics of Medical Imaging
Joseph Y. Lo; Taly Gilat Schmidt; Guang-Hong Chen, Editor(s)

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