PHASE-CONTRAST IMAGING USING POLYCHROMATIC HARD X-RAYS

IN conventional radiography, X-rays which pass through an object along different paths are differentially absorbed, and the intensity patter n of the emerging beam records the distribution of absorbing materials within the sample. An alternative approach is phase-contrast radiogra phy, which instead records variations of the phase of the emerging rad iation. Such an approach offers improved contrast sensitivity, especia lly when imaging weakly absorbing samples. Unfortunately, current phas e-contrast imaging techniques(1-11) generally require highly monochrom atic planewave radiation and sophisticated X-ray optics, so their use is greatly restricted. Here we describe and demonstrate a simplified s cheme for phase-contrast imaging based on an X-ray source having high spatial (but essentially no chromatic) coherence. The method is compat ible with conventional polychromatic microfocus X-ray tube sources, is well suited to large areas of irradiation, can operate with a lower a bsorbed dose than traditional X-ray imaging techniques, and should fin d broad application in clinical, biological and industrial settings.