It is very challenging to measure the chemical composition of hetero nanostructures in a reliable and quantitative manner. Here, we propose a novel and straightforward approach that can be used to quantify energy dispersive X-ray spectra acquired in a transmission electron microscope. Our method is based on a combination of electron tomography and the so-called ζ-factor technique. We will demonstrate the reliability of our approach as well as its applicability by investigating Au-Ag and Au-Pt hetero nanostructures. Given its simplicity, we expect that the method could become a new standard in the field of chemical characterization using electron microscopy.

The overall importance of x-ray phase contrast (XPC) imaging has grown substantially in the last decades, in particular with the recent advent of compact lab-based XPC systems. For optimizing the experimental XPC setup, as well as benchmarking and testing new acquisition and reconstruction techniques, Monte Carlo (MC) simulations are a valuable tool. GATE, an open source application layer on top of the Geant4 simulation software, is a versatile MC tool primarily intended for various types of medical imaging simulations. To our knowledge, however, there is no GATE-based academic simulation software available for XPC imaging. In this paper, we extend the GATE framework with new physics-based tools for accurate XPC simulations. Our approach combines Monte Carlo simulations in GATE for modelling the x-ray interactions in the sample with subsequent numerical wave propagation, starting from the GATE output.

Laboratory based X-ray micro-CT is a non-destructive testing method that enables three dimensional visualization and analysis of the internal and external morphology of samples. Although a wide variety of commercial scanners exist, most of them are limited in the number of degrees of freedom to position the source and detector with respect to the object to be scanned. Hence, they are less suited for industrial X-ray imaging settings that require advanced scanning modes, such as laminography, conveyor belt scanning, or time-resolved imaging (4DCT). We introduce a new X-ray scanner FleXCT that consists of a total of ten motorized axes, which allow a wide range of non-standard XCT scans such as tiled and off-centre scans, laminography, helical tomography, conveyor belt, dynamic zooming, and X-ray phase contrast imaging. Additionally, a new software tool ‘FlexRayTools’ was created that enables reconstruction of non-standard XCT projection data of the FleXCT instrument using the ASTRA Toolbox, a highly efficient and open source set of tools for tomographic projection and reconstruction.

The overall importance of x-ray phase-contrast imaging techniques has grown substantially due to their ability to generate contrast in a range of situations where traditional absorption imaging falls short. Monte Carlo simulations are a valuable tool for benchmarking and testing new acquisition and reconstruction techniques, as well as optimisation of the system and components design. GATE, an open source application layer on top of the Geant4 simulation software, is a versatile Monte Carlo tool for various types of medical imaging simulations. Currently, however, tools intended for phase-contrast imaging are not yet available within GATE. In this work, we introduce grating-based x-ray phase-contrast simulations in GATE, with specific focus on phantoms with fibrous microstructures. The simulations are based on a combination of Monte Carlo simulations in GATE for modelling the x-ray interactions in the sample, and subsequent numerical wave propagation in the interferometer, modelled in MATLAB. We show simulated computed tomography results for grating interferometry.

One of the most commonly used correction methods in X-ray imaging is flat field correction, which corrects for systematic inconsistencies, such as differences in detector pixel response. In conventional X-ray imaging, flat fields are acquired by exposing the detector without any object in the X-ray beam. However, in edge illumination Xray CT, which is an emerging phase contrast imaging technique, two masks are used to measure the refraction of the X-rays. These masks remain in place while the flat fields are acquired and thus influence the intensity of the flat fields. This influence is studied theoretically and validated experimentally using Monte Carlo simulations of an edge illumination experiment in GATE.

The design of new x-ray phase contrast imaging setups often relies on Monte Carlo simulations for prospective parameter studies. Monte Carlo simulations are known to be accurate but time consuming, leading to long simulation times, especially when many parameter variations are required. This is certainly the case for imaging methods relying on absorbing masks or gratings, with various tunable properties, such as pitch, aperture size, and thickness. In this work, we present the virtual grating approach to overcome this limitation. By replacing the gratings in the simulation with virtual gratings, the parameters of the gratings can be changed after the simulation, thereby significantly reducing the overall simulation time. The method is validated by comparison to explicit grating simulations, followed by representative demonstration cases.

X-ray phase contrast imaging is a rapidly evolving field, covering a range of different imaging methods. Its integration in the daily medical imaging routines, however, has proven to be difficult, despite encouraging results. In addition to the phase information, small angle X-ray scattering information is accessible through the so called dark field signal. The dark field signal holds great potential for lung imaging applications due to its ability to detect sub-pixel structures. Edge illumination, an incoherent form of phase contrast imaging, is particularly promising due to its low coherence requirements. A remaining issue in conventional edge illumination phase contrast imaging, however, is the absorption of photons by the detector mask, as these photons contribute to the dose but not to the image. In this work, we explore the dark field potential of a setup without detector mask for lung imaging through Monte Carlo simulations. In order to approximate the irregular shape of alveoli, surface roughness is taken into account.

Edge illumination is an emerging X-ray phase contrast imaging technique, which has been successfully transferred from synchrotron facilities to lab-based X-ray systems. Rather than installing a dedicated phase contrast system, our goal is to enable phase contrast imaging in a highly flexible X-ray CT system, FleXCT, a novel scanning system consisting of ten motorized axes. These axes allow movements of not only the sample stage, but also the source and detector. To enable phase contrast imaging, two gratings have to be incorporated in the FleXCT system. In this work, we report on the procedure to determine the optimal grating parameters, relying on numerical simulations. Optimal parameter values are presented for both FleXCT gratings.