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Abstract: Diffraction Enhanced Imaging (DEI) derives X-ray contrast from absorption, refraction, and extinction. While the refraction angle image of DEI represents the gradient of the projected mass density of the object, the absorption image measures the projected attenuation () of an object. Using a simple integral method it has been shown that a mass density image () can be obtained from the refraction angle image. It then is a simple matter to develop a combinational image by dividing these two images to create a μ/ρ image. The μ/ρ is a fundamental property of a material and is therefore useful for identifying the composition of an object. In projection X-ray imaging the μ/ρ image identifies the integrated composition of the elements along the beam path. When applied to DEI computed tomography (CT), the image identifies the composition in each voxel. This method presents a new type of spectroscopy based in radiography. We present the method of obtaining the compositional image, the results of experiments in which we verify the method with known standards and an application of the method to breast cancer imaging. [Copyright &y& Elsevier]

Abstract: In the experimental setup for Diffraction Enhanced Imaging (DEI) and its extension, Multiple-Image Radiography (MIR), it is essential to have the two or three crystals angularly aligned relative to one another around two orthogonal axes; the angle around an axis perpendicular to the diffraction plane (the Bragg angle) and also around a perpendicular axis in the plane (azimuthal angle). The appearance of the azimuthal angle (tilt error) will complicate the interpretation of the DEI/MIR images by creating a systematic change in the Bragg angle across the width of the imaging beam which in turn creates intensity variations across the imaging field. In this paper we present the effect of a tilt error, its estimation from the resulting images, and a method to correct such an error for the DEI/MIR images. The analysis and results will also apply to multiple crystal systems with tilt errors, such as monochromators on synchrotron beamlines. [Copyright &y& Elsevier]