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Title: Effects of signal diffusion on x-ray phase contrast images

Abstract

We discuss the problem of signal diffusion among neighbouring pixels in x-ray phase contrast imaging (XPCi) specifically for coded-aperture (CA) XPCi, but many of the discussed observations are directly transferable to other XPCi modalities. CA XPCi exploits the principle of pixel edge illumination by means of two CA masks. The first mask, placed in contact with the detector, creates insensitive regions between adjacent pixels; the second one, placed immediately before the sample, creates individual beams impinging on the boundaries between sensitive and insensitive regions on the detector, as created by the detector mask. In this way, edge illumination is achieved for all pixels of an area detector illuminated by a divergent and polychromatic beam generated by a conventional source. As the detector mask redefines the resolution properties of the detector, sample dithering can be used to effectively increase the system spatial resolution, without having to apply any post-processing procedure (e.g., deconvolution). This however creates artifacts in the form of secondary fringes (which have nothing to do with phase-related secondary fringes) if there is signal diffusion between adjacent pixels. In non-dithered images, signal diffusion between adjacent pixels causes a reduction in image contrast. This effect is investigated both theoretically and experimentally,more » and its direct implications on image quality are discussed. The interplay with the sample positioning with respect to the detector pixel matrix, which also has an effect on the obtained image contrast, is also discussed.« less

Authors:
; ; ;  [1]
  1. Department of Medical Physics and Bioengineering, UCL, Malet Place, Gower Street, London WC1E 6BT (United Kingdom)
Publication Date:
OSTI Identifier:
22063687
Resource Type:
Journal Article
Journal Name:
Review of Scientific Instruments
Additional Journal Information:
Journal Volume: 82; Journal Issue: 7; Other Information: (c) 2011 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0034-6748
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; DIFFUSION; IMAGE PROCESSING; IMAGES; PHOTOGRAPHIC FILM DETECTORS; PHOTON BEAMS; POSITIONING; SIGNALS; SPATIAL RESOLUTION; X RADIATION

Citation Formats

Ignatyev, K., Munro, P. R. T., Speller, R. D., and Olivo, A. Effects of signal diffusion on x-ray phase contrast images. United States: N. p., 2011. Web. doi:10.1063/1.3606442.
Ignatyev, K., Munro, P. R. T., Speller, R. D., & Olivo, A. Effects of signal diffusion on x-ray phase contrast images. United States. doi:10.1063/1.3606442.
Ignatyev, K., Munro, P. R. T., Speller, R. D., and Olivo, A. Fri . "Effects of signal diffusion on x-ray phase contrast images". United States. doi:10.1063/1.3606442.
@article{osti_22063687,
title = {Effects of signal diffusion on x-ray phase contrast images},
author = {Ignatyev, K. and Munro, P. R. T. and Speller, R. D. and Olivo, A.},
abstractNote = {We discuss the problem of signal diffusion among neighbouring pixels in x-ray phase contrast imaging (XPCi) specifically for coded-aperture (CA) XPCi, but many of the discussed observations are directly transferable to other XPCi modalities. CA XPCi exploits the principle of pixel edge illumination by means of two CA masks. The first mask, placed in contact with the detector, creates insensitive regions between adjacent pixels; the second one, placed immediately before the sample, creates individual beams impinging on the boundaries between sensitive and insensitive regions on the detector, as created by the detector mask. In this way, edge illumination is achieved for all pixels of an area detector illuminated by a divergent and polychromatic beam generated by a conventional source. As the detector mask redefines the resolution properties of the detector, sample dithering can be used to effectively increase the system spatial resolution, without having to apply any post-processing procedure (e.g., deconvolution). This however creates artifacts in the form of secondary fringes (which have nothing to do with phase-related secondary fringes) if there is signal diffusion between adjacent pixels. In non-dithered images, signal diffusion between adjacent pixels causes a reduction in image contrast. This effect is investigated both theoretically and experimentally, and its direct implications on image quality are discussed. The interplay with the sample positioning with respect to the detector pixel matrix, which also has an effect on the obtained image contrast, is also discussed.},
doi = {10.1063/1.3606442},
journal = {Review of Scientific Instruments},
issn = {0034-6748},
number = 7,
volume = 82,
place = {United States},
year = {2011},
month = {7}
}