Abstract
Following the first experimental demonstration of x-ray speckle-based multimodal imaging using a polychromatic beam [I. Zanette et al., Phys. Rev. Lett. 112(25), 253903 (2014)], we present a simulation study on the effects of a polychromatic x-ray spectrum on the performance of this technique. We observe that the contrast of the near-field speckles is only mildly influenced by the bandwidth of the energy spectrum. Moreover, using a homogeneous object with simple geometry, we characterize the beam hardening artifacts in the reconstructed transmission and refraction angle images, and we describe how the beam hardening also affects the dark-field signal provided by speckle tracking. This study is particularly important for further implementations and developments of coherent speckle-based techniques at laboratory x-ray sources.
Highlights
X-ray phase-contrast and dark-field imaging have proven to be reliable imaging methods and are used, in particular, in cases where conventional absorption contrast can only yield poor results, i.e., to visualize details in samples with little density variations, such as soft tissue specimens
Propagation- and grating-based methods have successfully been implemented at laboratory sources because of their tolerance to divergent and polychromatic beams
Implementations of x-ray speckle imaging with a polychromatic laboratory source have been reported
Summary
X-ray phase-contrast and dark-field (or visibility-contrast) imaging have proven to be reliable imaging methods and are used, in particular, in cases where conventional absorption contrast can only yield poor results, i.e., to visualize details in samples with little density variations, such as soft tissue specimens In these samples, phase-contrast imaging can yield superior results because of its much higher sensitivity to small density differences, while darkfield imaging gives information on a sub-pixel scale by revealing the scattering strength of structures in the sample, which cannot be resolved directly by the detector, such as fibers, cracks, and nanopores.. Phase-contrast imaging can yield superior results because of its much higher sensitivity to small density differences, while darkfield imaging gives information on a sub-pixel scale by revealing the scattering strength of structures in the sample, which cannot be resolved directly by the detector, such as fibers, cracks, and nanopores.2 Several methods using these advanced imaging modalities have been developed, including propagation-based, analyzer-based, and grating-based methods..
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