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Photon Counting X-ray Detector Systems
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media. (STC)
2005 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This licentiate thesis concerns the development and characterisation of X-ray imaging detector systems. “Colour” X-ray imaging opens up new perspectives within the fields of medical X-ray diagnosis and also in industrial X-ray quality control. The difference in absorption for different “colours” can be used to discern materials in the object. For instance, this information might be used to identify diseases such as brittle-bone disease. The “colour” of the X-rays can be identified if the detector system can process each X-ray photon individually. Such a detector system is called a “single photon processing” system or, less precise, a “photon counting system”.

With modern technology it is possible to construct photon counting detector systems that can resolve details to a level of approximately 50 µm. However with such small pixels a problem will occur. In a semiconductor detector each absorbed X-ray photon creates a cloud of charge which contributes to the picture achieved. For high photon energies the size of the charge cloud is comparable to 50 µm and might be distributed between several pixels in the picture. Charge sharing is a key problem since, not only is the resolution degenerated, but it also destroys the “colour” information in the picture.

The problem involving charge sharing which limits “colour” X-ray imaging is discussed in this thesis. Image quality, detector effectiveness and “colour correctness” are studied on pixellated detectors from the MEDIPIX collaboration. Characterisation measurements and simulations are compared to be able to understand the physical processes that take place in the detector. Simulations can show pointers for the future development of photon counting X-ray systems. Charge sharing can be suppressed by introducing 3D-detector structures or by developing readout systems which can correct the crosstalk between pixels.

Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University , 2005.
Series
Mid Sweden University licentiate thesis, ISSN 1652-8948 ; 2
Keyword [en]
Monte Carlo simulation, Three-dimensional, Energy weighting, X-ray, Pixel detector, Charge sharing, Imaging, Medipix, Spectroscopy, Dental diagnosis, Image quality
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:miun:diva-41ISBN: 91-85317-01-2 (print)OAI: oai:DiVA.org:miun-41DiVA: diva2:2000
Presentation
2005-02-11, M102, Humlegården, Holmgatan 10, Sundsvall, 10:15 (English)
Opponent
Supervisors
Available from: 2007-11-29 Created: 2007-11-29 Last updated: 2011-02-06Bibliographically approved
List of papers
1. Monte Carlo simulation of the response of a pixellated 3D photodetector in silicon
Open this publication in new window or tab >>Monte Carlo simulation of the response of a pixellated 3D photodetector in silicon
2002 (English)In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 487, no 1-2, 136-141 p.Article in journal (Refereed) Published
Abstract [en]

The charge transport and X-ray photon absorption in three-dimensional (3D) X-ray pixel detectors have been studied using numerical simulations. The charge transport has been modelled using the drift-diffusion simulator MEDICI, while photon absorption has been studied using MCNP. The response of the entire pixel detector system in terms of charge sharing, line spread function and modulation transfer function, has been simulated using a system level Monte Carlo simulation approach. A major part of the study is devoted to the effect of charge sharing on the energy resolution in 3D-pixel detectors. The 3D configuration was found to suppress charge sharing much better than conventional planar detectors.

Keyword
Charge sharing, Detector, Monte Carlo simulation, Silicon, Three-dimensional, X-ray
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-377 (URN)10.1016/S0168-9002(02)00957-9 (DOI)000177177500022 ()2-s2.0-0037063080 (Scopus ID)877 (Local ID)877 (Archive number)877 (OAI)
Conference
3rd International Workshop on Radiation Imaging Detectors; Orosai, Sardinia; Italy; 23 September 2001 through 27 September 2001
Note

3rd International Workshop on Radiation Imaging Detectors, Sep 23-27, 2001, orosei, Italy

Available from: 2008-12-11 Created: 2008-12-11 Last updated: 2016-10-25Bibliographically approved
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Citation style
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