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Energy-resolved CT imaging with a photon-counting silicon-strip detector
KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging.ORCID iD: 0000-0002-5092-8822
KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging.
KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging.
KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging.
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2014 (English)In: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 59, no 22, 6709-6727 p.Article in journal (Refereed) Published
Abstract [en]

Photon-counting detectors are promising candidates for use in the next generation of x-ray computed tomography (CT) scanners. Among the foreseen benefits are higher spatial resolution, better trade-off between noise and dose and energy discriminating capabilities. Silicon is an attractive detector material because of its low cost, mature manufacturing process and high hole mobility. However, it is sometimes overlooked for CT applications because of its low absorption efficiency and high fraction of Compton scatter. The purpose of this work is to demonstrate that silicon is a feasible material for CT detectors by showing energy-resolved CT images acquired with an 80 kVp x-ray tube spectrum using a photon-counting silicon-strip detector with eight energy thresholds developed in our group. We use a single detector module, consisting of a linear array of 50 0.5 x 0.4 mm detector elements, to image a phantom in a table-top lab setup. The phantom consists of a plastic cylinder with circular inserts containing water, fat and aqueous solutions of calcium, iodine and gadolinium, in different concentrations. By using basis material decomposition we obtain water, calcium, iodine and gadolinium basis images and demonstrate that these basis images can be used to separate the different materials in the inserts. We also show results showing that the detector has potential for quantitative measurements of substance concentrations.

Place, publisher, year, edition, pages
2014. Vol. 59, no 22, 6709-6727 p.
Keyword [en]
photon counting, spectral CT, material decomposition, siliconstrip detector
National Category
Radiology, Nuclear Medicine and Medical Imaging
URN: urn:nbn:se:kth:diva-157026DOI: 10.1088/1361-6560/59/22/6709ISI: 000344091000005ScopusID: 2-s2.0-84908587151OAI: diva2:768835

QC 20141205

Available from: 2014-12-05 Created: 2014-12-04 Last updated: 2016-05-20Bibliographically approved
In thesis
1. Spectral Computed Tomography with a Photon-Counting Silicon-Strip Detector
Open this publication in new window or tab >>Spectral Computed Tomography with a Photon-Counting Silicon-Strip Detector
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Computed tomography (CT) is a widely used medical imaging modality. By rotating an x-ray tube and an x-ray detector around the patient, a CT scanner is able to measure the x-ray transmission from all directions and form an image of the patient’s interior. CT scanners in clinical use today all use energy-integrating detectors, which measure the total incident energy for each measurement interval. A photon-counting detector, on the other hand, counts the number of incoming photons and can in addition measure the energy of each photon by comparing it to a number of energy thresholds. Using photon- counting detectors in computed tomography could lead to improved signal-to-noise ratio, higher spatial resolution and improved spectral imaging which allows better visualization of contrast agents and more reliable quantitative measurements. In this Thesis, the feasibility of using a photon-counting silicon-strip detector for CT is investigated. In the first part of the Thesis, the necessary performance requirements on such a detector is investigated in two different areas: the detector element homogeneity and the capability of handling high photon fluence rates. A metric of inhomogeneity is proposed and used in a simulation study to evaluate different inhomogeneity compensation methods. Also, the photon fluence rate incident on the detector in a scanner in clinical use today is investigated for different patient sizes through dose rate measurements together with simulations of transmission through patient im- ages. In the second part, a prototype detector module is used to demonstrate new applications enabled by the energy resolution of the detector. The ability to generate material-specific images of contrast agents with iodine and gadolinium is demonstrated. Furthermore, it is shown theoretically and ex- perimentally that interfaces in the image can be visualized by imaging the so-called nonlinear partial volume effect. The results suggest that the studied silicon-strip detector is a promising candidate for photon-counting CT.  

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. 43 p.
TRITA-FYS, ISSN 0280-316X ; 2016:20
Photon-counting, silicon-strip detector, spectral computed tomography, ring artifacts, fluence rate, basis material decomposition, sub-pixel information
National Category
Other Physics Topics Medical Equipment Engineering
Research subject
urn:nbn:se:kth:diva-187263 (URN)978-91-7595-991-7 (ISBN)
Public defence
2016-06-14, FR4, Roslagstullsbacken 21, AlbaNova Universitetscentrum, Stockholm, 09:00 (English)
Available from: 2016-05-20 Created: 2016-05-18 Last updated: 2016-05-20Bibliographically approved

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Persson, MatsHuber, BenKarlsson, StaffanLiu, XuejinChen, HanXu, ChengYveborg, MoaBornefalk, HansDanielsson, Mats
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