We tested an X-ray interferometer fabricated to improve the spatial resolution of phase-contrast X-ray computed tomography
(CT). The main factor limiting the spatial resolution is the diffraction phenomenon in the crystal wafer of the interferometer. Improvement of the spatial resolution was attempted by thinning the wafer. A preliminary test was performed by checking interference patterns. Thinning the wafer from 1 to 0.24 mm showed clear improvement in the image quality.