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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]

Examines the use of asymmetric laue crystal in synchrotron X-rays. Measurement of the rocking curve; Factors controlling the angle of the lattice plane; Improvement on asymmetric laue crystal.

The refraction angle of x rays as they pass through a refractive prism is proportional to the square of the x-ray wavelength. This was used to discriminate between different harmonic orders, which have different energies, created by a two-crystal 111 monochromator [Z. Zhong, J. Appl. Crystallogr 33, 1082 (2000)]. Refractive prisms inserted between the two monochromator crystals allowed selection, among the 111, 333, 444, and 555 diffractions, in our diffraction enhanced imaging program at National Synchrotron Light Source’s X15A beamline, and facilitated convenient change of sensitivity in our efforts to optimize DEI system for mammography and other radiographic applications. The selection of 111 and 333 refractions were straightforward since the necessary angle of refraction is small. The challenge of selecting 444 and 555 reflections was met by designing an acrylic prism that offered an angle of refraction much larger than 10 μrad and was compact enough to be manipulated in the small space between the crystals. Examples are given on use of the prism for studying the effects of diffraction orders on DEI’s refraction and extinction contrasts. Its modes of operation and limitations are discussed. The principle of harmonics selection through prism and the specific design of the device could be relevant for other synchrotron monochromators that have a harmonics concern or can benefit from change of energy, through selection of harmonic orders, without changing crystals. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

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]

Carotid artery plaque instability can result in rupture and lead to ischaemic stroke. Stability of plaques appears to be a function of composition. Current non- invasive imaging techniques are limited in their ability to classify distinct histological regions within plaques. Phase-contrast (PC) X-ray imaging methods are an emerging class of techniques that have shown promise for identifying soft-tissue features without use of exogenous contrast agents. This is the first study to apply analyser-based X-ray PC imaging in CT mode to provide three-dimensional (3D) images of excised atherosclerotic plaques. The results provide proof of principle for this technique as a promising method for analysis of carotid plaque microstructure. Multiple image radiography CT (MIR-CT), a tomographic implementation of X-ray PC imaging that employs crystal optics, was employed to image excised carotid plaques. MIR-CT imaging yields three complementary images of the plaque's 3D X-ray absorption, refraction and scatter properties. These images were compared with histological sections of the tissue. X-ray PC images were able to identify the interface between the plaque and the medial wall. In addition, lipid-rich and highly vascularized regions were visible in the images as well as features depicting inflammation. This preliminary research shows MIR-CT imaging can reveal details about plaque structure not provided by traditional absorption-based X-ray imaging and appears to identify specific histological regions within plaques. This is the first study to apply analyser-based X-ray PC imaging to human carotid artery plaques to identify distinct soft-tissue regions. [ABSTRACT FROM AUTHOR]

Diffraction enhanced imaging (DEI), also called analyzer-based imaging (ABI), cultivated within the synchrotron community, has the potential to revolutionize medical imaging through reduced dose and enhanced contrast imaging. [ABSTRACT FROM AUTHOR]

Experiments and numerical simulations based on finite element modeling show that the x-ray intensity scattered by comparatively large nanostructures on a substrate is not simply related to their strain in experiments using either grazing incidence or exit because of multiple scattering effects. However, whatever the nanostructure size, the composition profiles are correctly extracted from grazing incidence multiwavelength anomalous scattering. These effects are illustrated for the structural analysis of Ge dome-shaped islands grown on Si(001). [ABSTRACT FROM AUTHOR]