Semiempirical criterion for eliminating wraparound artifacts in single-grid-based phase-contrast X-ray imaging

Abstract

Single-grid-based phase-contrast X-ray imaging (SG-PCXI) is a non-interferometric method for the simultaneous retrieval of absorption, phase-contrast (differential), and dark-field images from a single exposure with a common X-ray grid using a spatial harmonic imaging (SHI) technique. However, the retrieved images are often distorted by the wraparound artifacts that are caused by the spectral overlap of adjacent harmonic peaks in the Fourier domain, resulting in the degradation of image quality. In this study, a semiempirical criterion required for eliminating wraparound artifacts in SG-PCXI was established by considering two constraints: one to resolve periodic grid strips by the system resolution to use the SHI technique, and the other to ensure that the spectral contents of adjacent harmonic peaks are separated (not overlapped) to the greatest possible extent during data processing. Further, we assumed that the system resolution can be experimentally determined as the spatial frequency at a 10% modulation transfer function. To verify the efficacy of the semiempirical criterion, we conducted an experiment using a table-top setup, which primarily comprised a microfocus X-ray source with a 20 μm focal spot size, X-ray grids with strip densities of 150, 200, and 254 lines/inch, and a CMOS flat-panel detector with a 49.5 μm pixel size. The experimental measurements of the wraparound artifacts in our system setup were in good agreement with the semiempirical criterion over the entire range of test conditions, thus verifying its efficacy for SG-PCXI. Accordingly, the semiempirical criterion established in this study will be useful for designing a wraparound artifact-free system layout in SG-PCXI.