Phase-unwrapping of differential phase-contrast data using attenuation information

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

doi:10.1117/12.877945

15 March 2011 Phase-unwrapping of differential phase-contrast data using attenuation information

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

Author Affiliations +

Proceedings Volume 7962, Medical Imaging 2011: Image Processing; 79624R (2011) https://doi.org/10.1117/12.877945
Event: SPIE Medical Imaging, 2011, Lake Buena Vista (Orlando), Florida, United States

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.

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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, and J. Hornegger "Phase-unwrapping of differential phase-contrast data using attenuation information", Proc. SPIE 7962, Medical Imaging 2011: Image Processing, 79624R (15 March 2011); https://doi.org/10.1117/12.877945

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