X-ray phase contrast imaging (PCI) visualizes higher contrast than the conventional absorption imaging in biological soft tissues. In PCI, the grating-based interferometry has been attracting much attention because we can use the conventional laboratory X-ray tubes. However, unlike the conventional X-ray imaging, the measured fringe pattern is formed by three unknown variable-phase, absorption and visibility contrast. Therefore, we need to measure more than three fringe patterns by moving the grating, which is called as phase stepping. For a constant sub-micron accuracy of the phase stepping, the highly stable measurement system is required. In this paper we propose a single-shot method which needs only one fringe pattern. The proposed method consists of two steps. First, we compute the “rough” image using the measured fringe pattern under an assumption. Namely, a pixel and the surroundings on phase (also absorption and visibility) map have almost the same value. This assumption contributes to compensating for the lack of measured data. Second, to improve the quality of the “rough” map, we minimize the weighted least square error between the measured fringe pattern and the estimated one. The weight coefficients are computed from “rough” map using non-local approach of modern image processing in which the pixels with a similar value to the pixel of interested (where compute the phase) have larger weights. With these procedures, the discontinuous pixels are excluded from the calculation of the phase to improve the accuracy of obtained images. Some experimental results are presented to demonstrate the effectiveness of the proposed method.

Date Published: 1 March 2019
PDF: 6 pages
Proc. SPIE 10948, Medical Imaging 2019: Physics of Medical Imaging, 109485H (1 March 2019); doi: 10.1117/12.2513109

Published in SPIE Proceedings Vol. 10948:
Medical Imaging 2019: Physics of Medical Imaging
Taly Gilat Schmidt; Guang-Hong Chen; Hilde Bosmans, Editor(s)