Phase-contrast measurement using a grating interferometer. (a) The beam deflection caused by the sample is transformed into an intensity variation that is detected with a conventional two-dimensional x-ray detector. During a phase-stepping scan, grating G2 is moved stepwise perpendicular to the grating structures, while the intensity oscillation is recorded for each detector pixel. (b) Arrangement of the symmetric grating interferometer using a conventional x-ray tube source. The interferometer consists of two absorption gratings G0 and G2 and one phase grating G1.
Phase-contrast projections of a mobile phone. (a) Photograph with a rectangular box showing the location of (b) the conventional transmission image and (c) the phase-contrast image. The phase-contrast image shows the deflection angle in units of the phase shift of the oscillation in the phase-stepping scan.
CT reconstructions of a PMMA phantom. Shown are the (a) conventional reconstruction and (b) the phase-contrast reconstruction. The phantom consists of two PMMA cylinders of 30 mm diameter. The text PSI was milled into the upper cylinder on a CNC machine. Contrast is obtained between the air-filled letters and PMMA. Both images show cross sections for three orthogonal directions, the reconstructed slice (bottom left) and two longitudinal cross sections (top left, top right), as well as a 3D rendering (bottom right). The sticky tape used to attach the two cylinders to each other is visible in the conventional reconstruction as a small bright ring around the cylinder. The thickest part of the ring is found above the left side of the letter P where two tape layers overlap. The bottom cylinder was glued to a sample holder from aluminum. Sample holder and glue are visible at the bottom of the longitudinal cross sections.
Parameters of the constructed symmetric grating interferometer for 60 keV.
Material thickness with 10% transmission remaining for selected materials at 28 and 60 keV. The relative increase in the transmission thickness going from 28 to 60 keV is given by the ratio column.
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