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Proceedings Paper

Phase-unwrapping of differential phase-contrast data using attenuation information
Author(s): Wilhelm Haas; M. Bech; P. Bartl; F. Bayer; A. Ritter; T. Weber; G. Pelzer; M. Willner; K. Achterhold; J. Durst; T. Michel; M. Prümmer; F. Pfeiffer; G. Anton; J. Hornegger
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Paper Abstract

Phase-contrast imaging approaches suffer from a severe problem which is known in Magnetic Resonance Imaging (MRI) and Synthetic Aperture Radar (SAR) as phase-wrapping. This work focuses on an unwrapping solution for the grating based phase-contrast interferometer with X-rays. The approach delivers three types of information about the x-rayed object - the absorption, differential phase-contrast and dark-field information whereas the observed differential phase values are physically limited to the interval (-π, π]; values higher or lower than the interval borders are mapped (wrapped) back into it. In contrast to existing phase-unwrapping algorithms for MRI and SAR the presented algorithm uses the absorption image as additional information to identify and correct phase-wrapped values. The idea of the unwrapping algorithm is based on the observation that at locations with phase-wrapped values the contrast in the absorption image is high and the behavior of the gradient is similar to the real (unwrapped) phase values. This can be expressed as a cost function which has to be minimized by an integer optimizer. Applied on simulated and real datasets showed that 95.6% of phase-wraps were correctly unwrapped. Based on the results we conclude that it is possible to use the absorption information in order to identify and correct phase-wrapped values.

Paper Details

Date Published: 15 March 2011
PDF: 6 pages
Proc. SPIE 7962, Medical Imaging 2011: Image Processing, 79624R (15 March 2011); doi: 10.1117/12.877945
Show Author Affiliations
Wilhelm Haas, Friedrich-Alexander-Univ. Erlangen-Nürnberg (Germany)
M. Bech, Technische Univ. München (Germany)
P. Bartl, Friedrich-Alexander-Univ. Erlangen-Nürnberg (Germany)
F. Bayer, Friedrich-Alexander-Univ. Erlangen-Nürnberg (Germany)
A. Ritter, Friedrich-Alexander-Univ. Erlangen-Nürnberg (Germany)
T. Weber, Friedrich-Alexander-Univ. Erlangen-Nürnberg (Germany)
G. Pelzer, Friedrich-Alexander-Univ. Erlangen-Nürnberg (Germany)
M. Willner, Technische Univ. München (Germany)
K. Achterhold, Technische Univ. München (Germany)
J. Durst, Friedrich-Alexander-Univ. Erlangen-Nürnberg (Germany)
T. Michel, Friedrich-Alexander-Univ. Erlangen-Nürnberg (Germany)
M. Prümmer, Friedrich-Alexander-Univ. Erlangen-Nürnberg (Germany)
F. Pfeiffer, Technische Univ. München (Germany)
G. Anton, Friedrich-Alexander-Univ. Erlangen-Nürnberg (Germany)
J. Hornegger, Friedrich-Alexander-Univ. Erlangen-Nürnberg (Germany)
Erlangen Graduate School in Advanced Optical Technologies (Germany)

Published in SPIE Proceedings Vol. 7962:
Medical Imaging 2011: Image Processing
Benoit M. Dawant; David R. Haynor, Editor(s)

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