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Use of depth information from in-depth photon counting detectors for x-ray spectral imaging: A preliminary simulation study
KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging.
KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging.ORCID iD: 0000-0002-3039-9791
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2014 (English)In: Medical Imaging 2014: Physics of Medical Imaging, SPIE - International Society for Optical Engineering, 2014, 90333E- p.Conference paper, Published paper (Refereed)
Abstract [en]

Purpose: Photon counting x-ray detectors (PCXD) may improve dose-efficiency but are hampered by limited count rate. They generally have imperfect energy response. Multi-layer ("in-depth") detectors have been proposed to enable higher count rates but the potential benefit of the depth information has not been explored. We conducted a simulation study to compare in-depth detectors against single layer detectors composed of common materials. Both photon counting and energy integrating modes were studied. Methods: Polyenergetic transmissions were simulated through 25cm of water and 1cm of calcium. For PCXD composed of Si, GaAs or CdTe a 120kVp spectrum was used. For energy integrating x-ray detectors (EIXD) made from GaAs, CdTe or CsI, spectral imaging was done using 80 and 140kVp and matched dose. Semi-ideal and phenomenological energy response models were used. To compare these detectors, we computed the Cramér-Rao lower bound (CRLB) of the variance of basis material estimates. Results: For PCXDs with perfect energy response, depth data provides no additional information. For PCXDs with imperfect energy response and for EIXDs the improvement can be significant. E.g., for a CdTe PCXD with realistic energy response, depth information can reduce the variance by 50%. The improvement depends on the x-ray spectrum. For a semi-ideal Si detector and a narrow x-ray spectrum the depth information has minimal advantage. For EIXD, the in-depth detector has consistent variance reduction (15% and 17%19% for water and calcium, respectively). Conclusions: Depth information is beneficial to spectral imaging for both PCXD and EIXD. The improvement depends critically on the detector energy response.

Place, publisher, year, edition, pages
SPIE - International Society for Optical Engineering, 2014. 90333E- p.
Series
Progress in Biomedical Optics and Imaging, ISSN 1605-7422 ; 9033
Keyword [en]
CRLB, Energy Response Function, Material Decomposition, Photon-counting Detector, Spectral CT
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
URN: urn:nbn:se:kth:diva-146793DOI: 10.1117/12.2042839ISI: 000338775800117Scopus ID: 2-s2.0-84901645515ISBN: 978-081949826-7 (print)OAI: oai:DiVA.org:kth-146793DiVA: diva2:725447
Conference
Medical Imaging 2014: Physics of Medical Imaging; San Diego, CA; United States; 17 February 2014 through 20 February 2014
Note

QC 20140616

Available from: 2014-06-16 Created: 2014-06-16 Last updated: 2015-10-05Bibliographically approved

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