title: Spectral Computed Tomography at High Photon Fluxes
creator: Rink, Kristian
subject: ddc-000
subject: 000 Generalities, Science
subject: ddc-500
subject: 500 Natural sciences and mathematics
subject: ddc-530
subject: 530 Physics
subject: ddc-600
subject: 600 Technology (Applied sciences)
description: The development of pixelated photon counting semiconductor detectors enables to resolve the spectral composition of the incident photons in X-ray imaging, provided that the detector is operated in the absence of pulse pile-up and sensor polarisation. The purpose of this study is to examine the imaging properties of Medipix2 MXR detectors under high photon fluxes, which do not meet this requirement.   At first, it is shown that the critical photon flux, at which the detector’s linearity breaks down, can be shifted towards higher values by increasing the IKrum current in the charge sensitive preamplifier, which corresponds to reducing the pulse shaping time. The negative impact of this procedure on the detector’s spectroscopic performance seems only moderate.  Furthermore, the deviation from an ideal linear response is determined as a function of the photon flux. The deviations are used to correct single projections and eventually acquire spectral CT images at high photon fluxes which contain corrected absorption coefficients. Thus, K-edge imaging with the contrast agents iodine and gadolinium can be performed at high photon fluxes. It is shown that the spectroscopic information vanishes for energy ranges, which correspond to energies higher than approximately the mean photon energy of the incident spectrum.
date: 2016
type: Master's thesis
type: info:eu-repo/semantics/masterThesis
type: NonPeerReviewed
format: application/pdf
identifier: https://archiv.ub.uni-heidelberg.de/volltextserverhttps://archiv.ub.uni-heidelberg.de/volltextserver/21616/1/Masterarbeit_Kristian_Rink.pdf
identifier: DOI:10.11588/heidok.00021616
identifier: urn:nbn:de:bsz:16-heidok-216166
identifier:   Rink, Kristian  (2016) Spectral Computed Tomography at High Photon Fluxes.  [Master's thesis]     
relation: https://archiv.ub.uni-heidelberg.de/volltextserver/21616/
rights: info:eu-repo/semantics/openAccess
rights: http://archiv.ub.uni-heidelberg.de/volltextserver/help/license_urhg.html
language: eng