Low dose single step grating based X-ray phase contrast imaging

Abstract

Phase sensitive X-ray imaging methods can provide substantially increased contrast over conventional absorption based imaging, and therefore new and otherwise inaccessible information. The use of gratings as optical elements in hard X-ray phase imaging overcomes some of the problems that have impaired the wider use of phase contrast in X-ray radiography and tomography. So far, to separate the phase information from other contributions detected with a grating interferometer, a phase-stepping approach has been considered, which implies the acquisition of multiple radiographic projections. Here,an innovative, highly sensitive X-ray tomographic phase contrast imaging approach is presented based on grating interferometry, which extracts the phase contrast signal without the need of phase stepping. Compared to the existing phase step approach, the main advantage of this new method dubbed 'reverse projection' is the significantly reduced delivered dose, without degradation of the image quality. The new technique sets the pre-requisites for future fast and low dose phase contrast imaging methods, fundamental for imaging biological specimens and in-vivo studies.

Description

technical field [0001] The present invention relates to methods and systems for low-dose single-step grating-based X-ray phase contrast imaging. Background technique [0002] It is well known that, unlike conventional visible light optics, the refractive index in X-ray optics is very close to and less than unity because X-ray photon energies are often much larger than atomic resonance energies. In a first approximation, for small and negligible anisotropy in the medium, the complex form of the refractive index can be used to represent the optical properties of the tissue, including X-ray absorption: , where δ is the reduction in the real part of the refractive index, which characterizes the phase-shifting properties, and the imaginary part β, describes the absorption properties of the sample. In conventional absorption-based radiography, X-ray phase shift information is usually not directly used for pattern reconstruction. However, at photon energies greater than 10 keV a...

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Problems solved by technology

[0007] Clearly, this method is burdened with limitations both in the (long

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