DEMONSTRATION OF PHASE-CONTRAST X-RAY COMPUTED-TOMOGRAPHY USING AN X-RAY INTERFEROMETER

Phase-contrast X-ray computed tomography (PCX-CT) using an X-ray inter ferometer is introduced for observing a density distribution inside an organic material. PCX-CT images are compared with an absorption-contr ast X-ray CT image and shown to be highly sensitive. To convert an int erference pattern into an image of phase-shift distribution, which is put into a CT algorithm, the author applied subfringe analysis techniq ues, such as the Fourier-transform method and the fringe scanning meth od. In the case presented here, a plastic sphere is used as a test sam ple, and the resulting spatial resolution of the PCX-CT image is less than 40 mu m. The signal-to-noise ratio (S/N) for the PCX-CT image is increased to ten times that for an absorption-contrast CT image. The S /N can be further increased by suppressing the movement of the interfe rence pattern caused by air now around the interferometer.