Phase Imaging with an X-ray Talbot Interferometer

X-ray Talbot interferometry (XTI) is described as a novel phase-sensitive X-ray imaging method. XTI uses two transmission gratings, and therefore in principle it functions with cone-beam X-rays of a broad energy band width, allowing its instrumentation with a compact X-ray source. Because an amplitude transmission grating is needed, X-ray lithography and electrochemical gold plating were employed to fabricate a high-aspect-ratio pattern. The performance of the phase imaging with XTI was tested using synchrotron radiation, and its high sensitivity was demonstrated by the observation of biological tissues. INTRODUCTION Since the middle of the 90’s, X-ray phase-sensitive imaging, including phase tomography, has attracted attention, because the sensitivity in X-ray transmission imaging is much improved, compared with that of the conventional method that relies on absorption for contrast generation. In order to generate a contrast depending on the shift of X-ray phase caused by an object, several techniques have been developed so far. A crystal X-ray interferometer was first used in this field, and another method using crystals was also proposed to select refracted X-rays. Because the methods use crystal optics under the Bragg diffraction condition, monochromatic X-ray plane wave is needed. Bright X-ray source is therefore necessary and, as a matter of fact, synchrotron radiation is used to record an image with a practical exposure time. Another method uses no optics provided that X-ray spatial coherence is sufficiently high. In this case, contrast is generated by Fresnel diffraction, and the contrast outlines the surface of an object and structural boundaries in it. Normally, the width of the outlines is several microns, and therefore a high resolution image detector is preferred to resolve them. This implies that sufficient flux is needed into a small pixel. Bright X-ray source such as synchrotron radiation is therefore mainly used. Although an exception, which has been commercialized in Japan, used an image detector with a pixel larger than ten microns, the contribution of the X-ray phase contrast 21 Copyright ©JCPDS-International Centre for Diffraction Data 2006 ISSN 1097-0002 Advances in X-ray Analysis, Volume 49