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Correction of phase wrapping artifacts in grating-based hard X-ray tomography

DOI: 10.1117/12.2530709 DOI Help

Authors: Griffin Rodgers (University of Basel) , Georg Schulz (University of Basel) , Hans Deyhle (University of Basel; Diamond Light Source) , Shashidhara Marathe (Diamond Light Source) , Christos Bikis (University of Basel) , Bert Muller (University of Basel) , Timm Weitkamp (Synchrotron SOLEIL)
Co-authored by industrial partner: No

Type: Conference Paper
Conference: Developments in X-Ray Tomography XII
Peer Reviewed: No

State: Published (Approved)
Published: September 2019
Diamond Proposal Number(s): 19829

Abstract: X-ray grating interferometry (XGI) is a phase-contrast imaging technique that allows for a quantitative measurement of the refractive index with high density resolution in a model-independent manner—i.e. without a priori knowledge of the specimen composition. However, the retrieval of the X-ray wavefront phase shift relies on the accurate measurement of the interference pattern phase shift, making XGI vulnerable to phase wrapping when the interference pattern phase shift, related to the derivative of the wavefront phase shift, is large. Standard procedure for avoiding phase wrapping involves submerging the specimen in a water bath to reduce the mismatch of the index of refraction at the boundaries, but this requires a top-down rotation stage and is susceptible to gas bubble formation inside the water bath. Our team has presented an algorithm to remove phase wrapping artifacts for cylindrically shaped specimens that is applied to the phase-retrieved sinogram. This algorithm models and replaces phase-wrapped data to prevent the spread of “cupping” artifacts due to the integration of the differential phase during reconstruction. We give a criterion for selecting the modeling parameters so that the resulting measurement of the index of refraction matches the results of measurements without phase wrapping. We also apply this technique to cases where phase wrapping occurs at multiple interfaces. This algorithm allows for XGI measurements without a water bath and top-down rotation stage at synchrotron and laboratory facilities, especially as sensitivity increases.

Journal Keywords: X-ray phase tomography; X-ray grating interferometry; phase wrapping; artifact correction; algorithms

Subject Areas: Technique Development, Mathematics

Instruments: I13-2-Diamond Manchester Imaging