Design optimization of a periodic microstructured array anode for hard x-ray grating interferometry

High energy x-ray Talbot-Lau interferometer employing a microarray anode-structured target source to extend the field of view

Objective. High energy and large field of view (FOV) phase contrast imaging is crucial for biological and even medical applications. Although some works have devoted to achieving a large FOV at high energy through bending gratings and so on, which would be extremely challenging in medical high energy imaging.Approach.We analyze the angular shadowing effect of planar gratings in high-energy x-ray Talbot-Lau interferometer (XTLI). Then we design and develop an inverse XTLI coupled with a microarray anode-structured target source to extend the FOV at high energy.Main results.Our experimental results demonstrate the benefit of the source in the inverse XTLI and a large FOV of 106.6 mm in the horizontal direction is achieved at 40 keV. Based on this system, experiments of a mouse demonstrate the potential advantage of phase contrast mode in imaging lung tissue.Significance.We extend the FOV in a compact XTLI using a microarray anode-structured target source coupled with an inverse geometry, which eliminates grating G0 and relaxes the fabrication difficulty of G2. We believe the established design idea and imaging system would facilitate the wide applications of XTLI in high energy phase contrast imaging.

High-resolution multicontrast tomography with an X-ray microarray anode-structured target source

Talbot–Lau interferometry (TLI) holds remarkable potential for multicontrast X-ray imaging but suffers from technical challenges associated with microfabrication and limited efficiency. We tackle the frontier challenges in this field by developing a microarray anode–structured target source with a built-in structured illumination scheme. Our development facilitates high-resolution and high-sensitivity TLI imaging without the absorption source grating. We demonstrate the tri-contrast tomography capability with a Drum fish tooth specimen and separate the biological features with different combinations of physical properties. Our approach not only addresses the long-standing challenges in the field of X-ray TLI phase-contrast imaging but also features a compact setup that can potentially be made broadly available to academia research and industrial applications.

Multicontrast X-ray imaging with high resolution and sensitivity using Talbot–Lau interferometry (TLI) offers unique imaging capabilities that are important to a wide range of applications, including the study of morphological features with different physical properties in biological specimens. The conventional X-ray TLI approach relies on an absorption grating to create an array of micrometer-sized X-ray sources, posing numerous limitations, including technical challenges associated with grating fabrication for high-energy operations. We overcome these limitations by developing a TLI system with a microarray anode–structured target (MAAST) source. The MAAST features an array of precisely controlled microstructured metal inserts embedded in a diamond substrate. Using this TLI system, tomography of a Drum fish tooth with high resolution and tri-contrast (absorption, phase, and scattering) reveals useful complementary structural information that is inaccessible otherwise. The results highlight the exceptional capability of high-resolution multicontrast X-ray tomography empowered by the MAAST-based TLI method in biomedical applications.

A method for material decomposition and quantification with grating based phase CT

Material decomposition (MD) is an important application of computer tomography (CT). For phase contrast imaging, conventional MD methods are categorized into two types with respect to different operation sequences, i.e., “before” or “after” image reconstruction. Both categories come down to two-step methods, which have the problem of noise amplification. In this study, we incorporate both phase and absorption (PA) information into MD process, and correspondingly develop a simultaneous algebraic reconstruction technique (SART). The proposed method is referred to as phase & absorption material decomposition-SART (PAMD-SART). By iteratively solving an optimization problem, material composition and substance quantification are reconstructed directly from absorption and differential phase projections. Comparing with two-step MD, the proposed one-step method is superior in noise suppression and accurate decomposition. Numerical simulations and synchrotron radiation based experiments show that PAMD-SART outperforms the classical MD method (image-based and dual-energy CT iterative method), especially for the quantitative accuracy of material equivalent atomic number.

Dual phase grating based X-ray differential phase contrast imaging with source grating: theory and validation

In this work, we developed a new theoretical framework using wave optics to explain the working mechanism of the grating based X-ray differential phase contrast imaging (XPCI) interferometer systems consist of more than one phase grating. Under the optical reversibility principle, the wave optics interpretation was simplified into the geometrical optics interpretation, in which the phase grating was treated as a thin lens. Moreover, it was derived that the period of an arrayed source, e.g., the period of a source grating, is always equal to the period of the diffraction fringe formed on the source plane. When a source grating is utilized, the theory indicated that it is better to keep the periods of the two phase gratings different to generate large period diffraction fringes. Experiments were performed to validate these theoretical findings.

Quantitative analysis of a micro array anode structured target for hard x-ray grating interferometry

Talbot-Lau interferometry (TLI) provides additional contrast modes for x-ray imaging that are complementary to conventional absorption radiography. TLI is particularly interesting because it is one of the few practical methods for realizing phase contrast with x-rays that is compatible with large-spot high power x-ray sources. A novel micro array anode structured target (MAAST) x-ray source offers several advantages for TLI over the conventional combination of an extended x-ray source coupled with an absorption grating including higher flux and larger field of view, and these advantages become more pronounced for x-ray energies in excess of 30 keV. A Monte Carlo simulation was performed to determine the optimal parameters for a MAAST source for use with TLI. It was found that the both spatial distribution of x-ray production and the number of x-ray produced in the MAAST have a strong dependence on the incidence angle of the electron beam.

Clinical Micro-CT Empowered by Interior Tomography, Robotic Scanning, and Deep Learning

While micro-CT systems are instrumental in preclinical research, clinical micro-CT imaging has long been desired with cochlear implantation as a primary application. The structural details of the cochlear implant and the temporal bone require a significantly higher image resolution than that (about 0.2 mm) provided by current medical CT scanners. In this paper, we propose a clinical micro-CT (CMCT) system design integrating conventional spiral cone-beam CT, contemporary interior tomography, deep learning techniques, and the technologies of a micro-focus X-ray source, a photon-counting detector (PCD), and robotic arms for ultrahigh-resolution localized tomography of a freely-selected volume of interest (VOI) at a minimized radiation dose level. The whole system consists of a standard CT scanner for a clinical CT exam and VOI specification, and a robotic micro-CT scanner for a local scan of high spatial and spectral resolution at minimized radiation dose. The prior information from the global scan is also fully utilized for background compensation of the local scan data for accurate and stable VOI reconstruction. Our results and analysis show that the proposed hybrid reconstruction algorithm delivers accurate high-resolution local reconstruction, and is insensitive to the misalignment of the isocenter position, initial view angle and scale mismatch in the data/image registration. These findings demonstrate the feasibility of our system design. We envision that deep learning techniques can be leveraged for optimized imaging performance. With high-resolution imaging, high dose efficiency and low system cost synergistically, our proposed CMCT system has great promise in temporal bone imaging as well as various other clinical applications.