Abstract
X-ray phase contrast imaging (XPCi) has been the hottest topic in x-ray imaging for over a decade. The excitement originates from the way in which image contrast is generated in XPCi, as this arises from the phase changes that x-rays undergo when crossing an object instead of relying on x-ray absorption. As a consequence, the contrast of all image details is highly enhanced, and features classically considered invisible become detectable. This solves the basic problem of conventional x-ray imaging i.e. poor image contrast arising from small absorption differences. This is extremely important whenever objects that differ little in x-ray absorption from their surrounding background have to be detected, e.g. in diagnostic radiology when soft tissue is imaged. Different XPCi methods were developed, based on freespace propagation, perfect crystals, gratings, etc - all of which are covered by patents which will be reviewed in the present paper. These methods, however, only work with synchrotron radiation (SR), which prevented real-world implementations of XPCi so far. A solution to this problem was developed at UCL, in the shape of a new XPCi approach based on coded apertures. This method is also covered by a patent which will be reviewed in this paper.
Keywords: Phase contrast imaging, X-ray imaging, free-space propagation, X-ray holography, Fresnel diffraction, interferometry, diffraction enhanced imaging, analyzer based imaging, Bonse/Hart interferometer, Talbot and Talbot/Lau interferometer, coded apertures
13