Mass density images from the diffraction enhanced imaging technique

Abstract

Conventional x-ray radiography measures the projected x-ray attenuation of an object. It requires attenuation differences to obtain contrast of embedded features. In general, the best absorption contrast is obtained at x-ray energies where the absorption is high, meaning a high absorbed dose. Diffraction-enhanced imaging (DEI) derives contrast from absorption, refraction, and extinction. The refraction angle image of DEI visualizes the spatial gradient of the projected electron density of the object. The projected electron density often correlates well with the projected mass density and projected absorption in soft-tissue imaging, yet the mass density is not an "energy"-dependent property of the object, as is the case of absorption. This simple difference can lead to imaging with less x-ray exposure or dose. In addition, the mass density image can be directly compared (i.e., a signal-to-noise comparison) with conventional radiography. We present the method of obtaining the mass density image, the results of experiments in which comparisons are made with radiography, and an application of the method to breast cancer imaging.

Phase-sensitive X-ray imaging of synovial joints

“…This is accomplished through two major factors based on the inherent properties of x-rays First, additional contrast is gained by preventing the majority of x-ray scatter from reaching the detector, a source of image degradation in conventional radiography. This is achieved by virtue of the angular sensitivity of the analyzer crystal, the distinguishing feature of ABI8,21,22,23. Secondly, the analyzer crystal allows detection of refracted x-rays and, thus, high sensitivity for delineating the boundaries between tissues having different refractive indices.…”

X-Ray Phase-Contrast Imaging with Nanoradian Angular Resolution

“…The refractive index decrement of a material, in fact, can be expressed as ¼ ðr 0 2 =2Þ e ' ðr 0 2 =4uÞ ¼ KðÞ, where r 0 is the classical electron radius and u is the unified atomic mass unit [21]. It can be shown that Á y ðÞ¼@ð R dzðÞÞ=@y¼KðÞ@ð R dzÞ=@y [22]; therefore, for a given angular resolution, the corresponding sensitivity to the object mass density variation is equal to ð@ð R dzÞ=@yÞ ¼ ðÁ y Þ=K. For instance, for an object of constant thickness of 1 cm and at an energy of 12 keV, a 13 nrad angular resolution leads to a detectable density gradient of about 9  10 À4 g=cm 3 mm À1 (e.g., a change of less than a thousandth of the density of water over a mm).…”

X‐ray imaging in advanced studies of ophthalmic diseases

“…It is possible by immersing the lenses in a medium of nearly the same density of the lens tissue, de-ionized water has been used for this purpose. 22 A clean uniform low-contrast image is shown in Fig. 3͑c͒ corresponding to the exposure of the healthy lens immersed in water.…”