Direct x-ray scattering signal measurements in edge-illumination/beam-tracking imaging and their interplay with the variance of the refraction signals

Abstract

X-ray dark-field or ultra-small angle scatter imaging has become increasingly important since the introduction of phase-based x-ray imaging and is having transformative impact in fields such as in vivo lung imaging and explosives detection. Here, we show that dark-field images acquired with the edge-illumination method (either in its traditional double mask or simplified single mask implementation) provide a direct measurement of the scattering function, which is unaffected by system-specific parameters such as the autocorrelation length. We show that this is a consequence both of the specific measurement setup and of the mathematical approach followed to retrieve the dark-field images. We show agreement with theoretical models for datasets acquired both with synchrotron and laboratory x-ray sources. We also introduce a new contrast mechanism, the variance of refraction, which is extracted from the same dataset and provides a direct link with the size of the scattering centers. We show that this can also be described by the same theoretical models. We study the behavior of both signals vs key parameters such as x-ray energy and scatterer radius. We find this allows quantitative and direct scattering measurements during imaging, with implications in all fields where dark-field imaging is used.

Reliable extraction of x-ray refraction and dark-field signals with a large field of view, multi-modal scanning system at spectral energies up to 150 kVp

“…This applies the effects of finite source size and detector resolution through convolutions [27]. To reproduce full multi-modal images a three-dimensional Monte-Carlo based approach was used based on an adaptation of McXtrace [28][29][30], which can generate multiple scattering events from randomly distributed particles smaller than the system's spatial resolution.…”