Quantitative characterization of fatty liver disease using x-ray scattering

Novel Zeff imaging method for deep internal areas using back-scattered X-rays

Elemental kinds, composition ratios, effective atomic number (Z_eff), and spatial distributions are the most basic information on materials and determine the physical and chemical properties of materials. X-ray fluorescence analysis have conventionally been used for elemental mapping, however maps on deep internal areas cannot be obtained because the escape depth of fluorescence X-rays is limited to a few mm from the surface of samples. Herein, we present a novel Z_eff imaging method that uses back-scattered X-rays. The intensity ratio of elastic and inelastic back-scattered X-rays depends on the atomic number (Z) of a single-element sample (Z_eff for a plural-element sample), and so Z_eff maps in deep areas can be obtained by spectrum analysis of the scattered high-energy incident X-rays. We demonstrated the feasibility of observing a phantom covered by an aluminum plate by using synchrotron radiation X-ray. A fine Z_eff map that can be used to identify materials was obtained from only front-side observation. The novel method opens up a new way for Z_eff mapping of deep areas of thick samples from front-side observation.