Advanced three-dimensional X-ray imaging unravels structural development of the human thymus compartments.

Background: The thymus, responsible for T cell-mediated adaptive immune system, has a structural and functional complexity that is not yet fully understood. Until now, thymic anatomy has been studied using histological thin sections or confocal microscopy 3D reconstruction, necessarily for limited volumes.

Methods: We used Phase Contrast X-Ray Computed Tomography to address the lack of whole-organ volumetric information on the microarchitecture of its structural components.

A compact system for intraoperative specimen imaging based on edge illumination x-ray phase contrast.

A significant number of patients receiving breast-conserving surgery (BCS) for invasive carcinoma and ductal carcinoma in situ (DCIS) may need reoperation following tumor-positive margins from final histopathology tests. All current intraoperative margin assessment modalities have specific limitations. As a first step towards the development of a compact system for intraoperative specimen imaging based on edge illumination x-ray phase contrast, we prove that the system's dimensions can be reduced without affecting imaging performance.

Retrieval of weak x-ray scattering using edge illumination.

X-ray phase contrast imaging provides additional modes of image contrast compared to conventional attenuation-based x-ray imaging, thus providing additional structural and functional information about the sample. The edge-illumination (EI) technique has been used to provide attenuation, refraction, and scattering contrast in both biological and non-biological samples. However, the retrieval of low scattering signals by fitting a single Gaussian remains problematic, principally due to the inability of the EI system to achieve perfect dark-field illumination.

Edge illumination X-ray phase tomography of multi-material samples using a single-image phase retrieval algorithm.

In this paper we present a single-image phase retrieval algorithm for multi-material samples, developed for the edge illumination (EI) X-ray phase contrast imaging method. The theoretical derivation is provided, along with any assumptions made. The algorithm is evaluated quantitatively using both simulated and experimental results from a computed tomography (CT) scan using the EI laboratory implementation.

Large field of view, fast and low dose multimodal phase-contrast imaging at high x-ray energy.

X-ray phase contrast imaging (XPCI) is an innovative imaging technique which extends the contrast capabilities of 'conventional' absorption based x-ray systems. However, so far all XPCI implementations have suffered from one or more of the following limitations: low x-ray energies, small field of view (FOV) and long acquisition times. Those limitations relegated XPCI to a 'research-only' technique with an uncertain future in terms of large scale, high impact applications.

A single-image retrieval method for edge illumination X-ray phase-contrast imaging: Application and noise analysis.

Purpose: Edge illumination (EI) X-ray phase-contrast imaging (XPCI) has been under development at University College London in recent years, and has shown great potential for both laboratory and synchrotron applications. In this work, we propose a new acquisition and processing scheme. Contrary to existing retrieval methods for EI, which require as input two images acquired in different setup configurations, the proposed approach can retrieve an approximate map of the X-ray phase from a single image, thus significantly simplifying the acquisition procedure and reducing data collection times.

Robust phase retrieval for high resolution edge illumination x-ray phase-contrast computed tomography in non-ideal environments.

Edge illumination x-ray phase contrast tomography is a recently developed imaging technique which enables three-dimensional visualisation of low-absorbing materials. Dedicated phase retrieval algorithms can provide separate computed tomography (CT) maps of sample absorption, refraction and scattering properties. In this paper we propose a novel "modified local retrieval" method which is capable of accurately retrieving sample properties in a range of realistic, non-ideal imaging environments.

Concept of contrast transfer function for edge illumination x-ray phase-contrast imaging and its comparison with the free-space propagation technique.

Previous studies on edge illumination (EI) X-ray phase-contrast imaging (XPCi) have investigated the nature and amplitude of the signal provided by this technique. However, the response of the imaging system to different object spatial frequencies was never explicitly considered and studied. This is required in order to predict the performance of a given EI setup for different classes of objects.

Asymmetric masks for laboratory-based X-ray phase-contrast imaging with edge illumination.

We report on an asymmetric mask concept that enables X-ray phase-contrast imaging without requiring any movement in the system during data acquisition. The method is compatible with laboratory equipment, namely a commercial detector and a rotating anode tube. The only motion required is that of the object under investigation which is scanned through the imaging system.

X-ray absorption, phase and dark-field tomography through a beam tracking approach.

We present a development of the beam-tracking approach that allows its implementation in computed tomography. One absorbing mask placed before the sample and a high resolution detector are used to track variations in the beam intensity distribution caused by the sample. Absorption, refraction, and dark-field are retrieved through a multi-Gaussian interpolation of the beam.

Achromatic approach to phase-based multi-modal imaging with conventional X-ray sources.

Compatibility with polychromatic radiation is an important requirement for an imaging system using conventional rotating anode X-ray sources. With a commercially available energy-resolving single-photon-counting detector we investigated how broadband radiation affects the performance of a multi-modal edge-illumination phase-contrast imaging system. The effect of X-ray energy on phase retrieval is presented, and the achromaticity of the method is experimentally demonstrated.

Single-image phase retrieval using an edge illumination X-ray phase-contrast imaging setup.

A method is proposed which enables the retrieval of the thickness or of the projected electron density of a sample from a single input image acquired with an edge illumination phase-contrast imaging setup. The method assumes the case of a quasi-homogeneous sample, i.e.

Inclusion of coherence in Monte Carlo models for simulation of x-ray phase contrast imaging.

Interest in phase contrast imaging methods based on electromagnetic wave coherence has increased significantly recently, particularly at X-ray energies. This is giving rise to a demand for effective simulation methods. Coherent imaging approaches are usually based on wave optics, which require significant computational resources, particularly for producing 2D images.

Phase retrieval through a one-dimensional ptychographic engine.

Ptychographic techniques are currently the subject of increasing scientific interest due to their capability to retrieve the complex transmission function of an object at very high resolution. However, they impose a substantial burden in terms of acquisition time and dimension of the scanned area, which limits the range of samples that can be studied. We have developed a new method that combines the ptychographic approach in one direction with Fresnel propagation in the other by employing a strongly asymmetric probe.

Spatial resolution of edge illumination X-ray phase-contrast imaging.

We analyze the spatial resolution of edge illumination X-ray phase-contrast imaging and its dependence upon various experimental parameters such as source size, source-to-sample and sample-to-detector distances, X-ray energy and size of the beam-shaping aperture. Different propagation regimes, as well as the beam divergence and polychromaticity encountered with laboratory sources, are also considered. We show that spatial resolution in edge illumination phase-contrast imaging presents peculiar features compared to other X-ray phase-contrast techniques.

Phase-contrast microscopy at high x-ray energy with a laboratory setup.

We report on the design and realization of an x-ray imaging system for quantitative phase-contrast microscopy at high x-ray energy with laboratory-scale instrumentation. Phase and amplitude were separated quantitatively at x-ray energies up to 80 keV with micrometric spatial resolution. The accuracy of the results was tested against numerical simulations, and the spatial resolution was experimentally quantified by measuring a Siemens star phase object.

Strategies for efficient and fast wave optics simulation of coded-aperture and other x-ray phase-contrast imaging methods.

We derive a Fourier formulation of coded-aperture x-ray phase-contrast imaging, based on the wave theory of optics in the Fresnel approximation. We use this model to develop a flexible, efficient, and general simulation algorithm that can be easily adapted to other implementations of x-ray phase contrast imaging. Likewise, the algorithm enables a simple extension to 2D aperture designs, different acquisition schemes, etc.

Keyhole electron diffractive imaging (KEDI).

Electron diffractive imaging (EDI) relies on combining information from the high-resolution transmission electron microscopy image of an isolated kinematically diffracting nano-particle with the corresponding nano-electron diffraction pattern. Phase-retrieval algorithms allow one to derive the phase, lost in the acquisition of the diffraction pattern, to visualize the actual atomic projected potential within the specimen at sub-ångström resolution, overcoming limitations due to the electron lens aberrations. Here the approach is generalized to study extended crystalline specimens.