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Title: High energy x-ray phase contrast CT using glancing-angle grating interferometers

Purpose: The authors present initial progress toward a clinically compatible x-ray phase contrast CT system, using glancing-angle x-ray grating interferometry to provide high contrast soft tissue images at estimated by computer simulation dose levels comparable to conventional absorption based CT. Methods: DPC-CT scans of a joint phantom and of soft tissues were performed in order to answer several important questions from a clinical setup point of view. A comparison between high and low fringe visibility systems is presented. The standard phase stepping method was compared with sliding window interlaced scanning. Using estimated dose values obtained with a Monte-Carlo code the authors studied the dependence of the phase image contrast on exposure time and dose. Results: Using a glancing angle interferometer at high x-ray energy (∼45 keV mean value) in combination with a conventional x-ray tube the authors achieved fringe visibility values of nearly 50%, never reported before. High fringe visibility is shown to be an indispensable parameter for a potential clinical scanner. Sliding window interlaced scanning proved to have higher SNRs and CNRs in a region of interest and to also be a crucial part of a low dose CT system. DPC-CT images of a soft tissue phantom at exposuresmore » in the range typical for absorption based CT of musculoskeletal extremities were obtained. Assuming a human knee as the CT target, good soft tissue phase contrast could be obtained at an estimated absorbed dose level around 8 mGy, similar to conventional CT. Conclusions: DPC-CT with glancing-angle interferometers provides improved soft tissue contrast over absorption CT even at clinically compatible dose levels (estimated by a Monte-Carlo computer simulation). Further steps in image processing, data reconstruction, and spectral matching could make the technique fully clinically compatible. Nevertheless, due to its increased scan time and complexity the technique should be thought of not as replacing, but as complimentary to conventional CT, to be used in specific applications.« less
Authors:
 [1] ; ;  [2] ; ;  [3] ;  [4]
  1. Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218 and Department of Physics and Institute of Medical Engineering, Technische Universität München, 85748 Garching (Germany)
  2. Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland 21218 (United States)
  3. Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218 (United States)
  4. Department of Physics and Institute of Medical Engineering, Technische Universität München, 85748 Garching (Germany)
Publication Date:
OSTI Identifier:
22251665
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 41; Journal Issue: 2; Other Information: (c) 2014 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; ABSORBED RADIATION DOSES; BONE JOINTS; COMPARATIVE EVALUATIONS; COMPUTERIZED SIMULATION; COMPUTERIZED TOMOGRAPHY; GRATINGS; IMAGE PROCESSING; IMAGES; INTERFEROMETERS; INTERFEROMETRY; MONTE CARLO METHOD; PHANTOMS; X-RAY TUBES