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Preliminary evaluation of a silicon strip detector for photon-counting spectral CT
KTH, School of Engineering Sciences (SCI), Physics, Medical Imaging.
KTH, School of Engineering Sciences (SCI), Physics, Medical Imaging.
KTH, School of Engineering Sciences (SCI), Physics, Medical Imaging.
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2012 (English)In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, Vol. 677, 45-51 p.Article in journal (Refereed) Published
Abstract [en]

An edge-on silicon strip detector designed for photon-counting spectral computed tomography (CT) is presented. Progress on the development of an application specific integrated circuit (ASIC) to process the pulses and sort them into energy bins is reported upon. The ASIC and detector are evaluated in terms of electronic noise, energy resolution, count rate linearity under high-frequency periodic pulses, threshold variation and gain. The high-frequency periodic pulses are injected both by means of an external pulse generator and a pulsed laser illuminating the silicon diode. The pulsed laser system has similar to 100 ps pulse width and thus generates near instantaneous pulses in the diode, thus mimicking real X-ray conversions. The evaluation shows a low thermal noise level of 0.77 key RMS, an energy resolution of 1.5 keV RMS when electron-hole pairs are generated in the detector diode by the laser injection. The test results furthermore indicate a good energy-discriminating capability of the detector with the thresholds spread out, assigning the external pulses to higher and higher energy bins as the pulse intensity is increased.

Place, publisher, year, edition, pages
2012. Vol. 677, 45-51 p.
Keyword [en]
Photon counting, Silicon strip detector, ASIC, Spectral computed tomography, Laser test
National Category
Atom and Molecular Physics and Optics Medical Engineering
URN: urn:nbn:se:kth:diva-96427DOI: 10.1016/j.nima.2012.02.034ISI: 000303790500010ScopusID: 2-s2.0-84858743996OAI: diva2:531430
QC 20120607Available from: 2012-06-07 Created: 2012-06-04 Last updated: 2012-11-23Bibliographically approved
In thesis
1. A Segmented Silicon Strip Detector for Photon-Counting Spectral Computed Tomography
Open this publication in new window or tab >>A Segmented Silicon Strip Detector for Photon-Counting Spectral Computed Tomography
2012 (English)Doctoral thesis, comprehensive summary (Other academic) [Artistic work]
Abstract [en]

Spectral computed tomography with energy-resolving detectors has a potential to improve the detectability of images and correspondingly reduce the radiation dose to patients by extracting and properly using the energy information in the broad x-ray spectrum. A silicon photon-counting detector has been developed for spectral CT and it has successfully solved the problem of high photon flux in clinical CT applications by adopting the segmented detector structure and operating the detector in edge-on geometry. The detector was evaluated by both the simulation and measurements.

The effects of energy loss and charge sharing on the energy response of this segmented silicon strip detector with different pixel sizes were investigated by Monte Carlo simulation and a comparison to pixelated CdTe detectors is presented. The validity of spherical approximations of initial charge cloud shape in silicon detectors was evaluated and a more accurate statistical model has been proposed.

A photon-counting energy-resolving application specific integrated circuit (ASIC) developed for spectral CT was characterized extensively by electrical pulses, pulsed laser and real x-ray photons from both the synchrotron and an x-ray tube. It has been demonstrated that the ASIC performs as designed. A noise level of 1.09 keV RMS has been measured and a threshold dispersion of 0.89 keV RMS has been determined. The count rate performance of the ASIC in terms of count loss and energy resolution was evaluated by real x-rays and promising results have been obtained.

The segmented silicon strip detector was evaluated using synchrotron radiation. An energy resolution of 16.1% has been determined with 22 keV photons in the lowest flux limit, which deteriorates to 21.5% at an input count rate of 100 Mcps mm−2. The fraction of charge shared events has been estimated and found to be 11.1% for 22 keV and 15.3% for 30 keV. A lower fraction of charge shared events and an improved energy resolution can be expected by applying a higher bias voltage to the detector.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. viii, 43 p.
Trita-FYS, ISSN 0280-316X ; 2012:88
photon counting, spectral computed tomography, silicon strip detector, ASIC, energy resolution, cadmium telluride, charge sharing, Monte Carlo simulation, synchrotron
National Category
Electrical Engineering, Electronic Engineering, Information Engineering Medical Equipment Engineering Medical Laboratory and Measurements Technologies Other Engineering and Technologies not elsewhere specified Radiology, Nuclear Medicine and Medical Imaging
urn:nbn:se:kth:diva-105614 (URN)978-91-7501-589-7 (ISBN)
Public defence
2012-12-14, FA32, AlbaNova University Center, KTH, Roslagstullsbacken 21, Stockholm, 13:15 (English)

QC 20121123

Available from: 2012-11-23 Created: 2012-11-23 Last updated: 2012-11-23Bibliographically approved

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Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Atom and Molecular Physics and OpticsMedical Engineering

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