A simulation tool for x-ray phase-contrast micro-CT featuring a small-pixel photon-counting detector

In this work, we performed a proof-of-concept experiment for phase-contrast x-ray imaging (PCXI) based on a single antiscatter grid and a polychromatic x-ray source. We established a table-top setup which consists of a focused-linear grid having a strip density of 200 lines/inch, a microfocus x-ray tube having a focal-spot size of about 5 μm, and a CMOS-type flat-panel detector having a pixel size of 48 μm. By using our prototype PCXI system and the Fourier demodulation technique, we successfully obtained attenuation, scattering, and differential phase-contrast images of improved visibility from the raw images of several selected samples at x-ray tube conditions of 90 kVp and 0.1 mAs. Further, fusion image (e.g., the attenuation＋the scattering) may have an advantage in displaying details of the sample's structures that are not clearly visible in the conventional attenuation image. Our experimental results indicate that single-grid-based approach seems a useful method for PCXI with great simplicity and minimal requirements on the setup alignment.

Introduction. X-ray inspection plays a unique role among all nondestructive testing methods for products and materials due to sufficiently high resolution and high penetrability. The present study is designed to consider the key features of microfocus X-ray sources, their areas of application, and main technical characteristics.Aim. The paper aims to systematize information and review modern X-ray radiation sources for the implementation of microfocus radiography.Materials and methods. The main designs of microfocus X-ray tubes (soldered and demountable) were considered relying on the experience of the St Petersburg State Electrotechnical University in developing and operating such equipment, as well as the experience and open-access publications of foreign researchers and developers. Data collected by leading research teams over the last ten years were analyzed.Results. The paper presents design features for each main type of microfocus X-ray tubes – soldered and demountable. All key structural elements are considered: an anode assembly, a cathode assembly, and a focusing system. The influence of anode target material on the X-ray tube radiation spectrum is shown. An original design of a liquid-anode microfocus X-ray tube is described to demonstrate its key features and advantages. In addition, the paper gives an overview of cathodes used in microfocus X-ray tubes (tungsten cathode and lanthanum hexaboride cathode), as well as providing a detailed description of calculations performed for focusing systems. Finally, the designs of modern X-ray tubes are presented.Conclusion. Modern X-ray tubes are high-tech products that allow for high-resolution research of various objects. The main advantage of testing performed with the use of X-ray tubes consists in high resolution (micron and submicron). The X-ray images of test objects used to determine their spatial resolution are given, which clearly illustrate the vast possibilities of this technology. In addition, ways to improve microfocus X-ray tubes are briefly discussed. The considered materials can be useful in selecting a nondestructive testing tool, as well as in developing and creating X-ray systems on the basis of microfocus X-ray tubes.

X-ray phase contrast imaging (XPCI) shows promising potential for analyzing blood vessels affected by a cardiovascular disease and may become a valuable diagnostic tool in angiography. Identifying the most suitable XPCI method for providing optimal visibility at clinically acceptable doses is critical. This study presents a two-dimensional computational simulation in Geant4 to quantitatively compare two XPCI techniques—Inline XPCI and Edge Illumination Single Mask (EISM)—in visualizing atherosclerotic plaques within the projected thickness image of the lumen. The angiographic specimen analyzed was modeled as three concentric cylinders, with half of the inner cylinder simulating the lumen of the blood vessel and the other half simulating an atherosclerotic plaque, the intermediate cylinder simulating the vessel tissue, and the outer cylinder simulating the tissue around the blood vessel. The computational setup consisted of a W-anode polychromatic x-ray source and a photon counting detector, with six spectra and three sample-to-detector distances (magnifications) considered. To enable a direct comparison with Inline XPCI, a multi-material phase retrieval procedure was adapted to work within the EISM framework. Estimates of absorbed dose were also performed for each XPCI method. The results demonstrate that Inline XPCI achieves a superior contrast-to-noise ratio (CNR) as compared to EISM in both analyzed regions of the recovered image, across all spectra and magnifications, while also exhibiting lower absorbed doses. The difference in CNR between the two XPCI methods decreases as the voltage and magnification increases. While Inline XPCI shows superior contrast in the plaque region for all voltages and magnifications studied, EISM excels in recovering the projected thickness in the free-plaque region, achieving better contrast at low voltages for any magnification.

Photon counting spectral detectors (PCSD) with smaller pixels and efficient sensors are desirable in applications like material decomposition and phase contrast x-ray imaging where discrimination of small signals and fine structure may be desired. Charge sharing in PCSD increases with decreasing pixel sizes and increasing sensor thickness such that the energy calibration or utility of spectral information can become a major hurdle. Utility of a combination of high Z sensors and small pixel sizes in PCSD is limited without efficient threshold calibration and charge sharing mitigation. Here we explore the utility of x-ray tube kVp as a reference to achieve efficient and fast calibration of PCSDs. This calibration method itself does not require rearranging the imaging setup and is not impacted by charge sharing. Our preliminary results indicate that this method can be useful even in scenarios where metal fluorescence and radioactive source based calibration techniques may be practically impossible. Our results are validated using x-ray fluorescence based calibration for a Silicon detector with moderate charge sharing. Calibration of a particularly challenging case of a Medipix2 detector (55 μm pixel size) with a 1 mm thick CdTe sensor and a Medipix3 detector with CdTe sensor is also demonstrated. A cross validation with K-edge identification of Gd is also presented here.

Operating the microfocus X-ray source at high power is required to achieve high temporal reso- lution. However, the thermal loading of the anode focal spot is a limiting factor in determining the maximum power of an x-ray tube. In this paper, a transmission window based on polycrystalline diamond, for improved brightness in microfocus X-ray tube was demonstrated. The polycrystalline diamond films which were depos- ited by hot filament chemical vapor deposition (HFCVD) approach revealed good intrinsic thermal properties. We developed a reliable method to fabricate and estimate the windows/target assembly, quantitatively ana- lyzed the anode heat load of the X-ray source operating under the electron beam irradiation, and then tested in a microfocus X-ray tube. It's believed that the experiment and calculation results presented here can be gen- erally applied for the design and the fabrication of a high brightness microfocus X-ray tube employing poly- crystalline diamond windows. KEYWORD: Microfocus X-ray source; Polycrystalline diamond film; Windows/target assembly; HFCVD; Anode heat load.

There is currently much interest in developing X-ray Phase Contrast Imaging (XPCI) systems which employ laboratory sources in order to deploy the technique in real world applications. The challenge faced by nearly all XPCI techniques is that of efficiently utilising the x-ray flux emitted by an x-ray tube which is polychromatic and possesses only partial spatial coherence. Techniques have, however, been developed which overcome these limitations. Such a technique, known as coded aperture XPCI, has been under development in our laboratories in recent years for application principally in medical imaging and security screening. In this paper we derive limitations imposed upon source polychromaticity and spatial extent by the coded aperture system. We also show that although other grating XPCI techniques employ a different physical principle, they satisfy design constraints similar to those of the coded aperture XPCI.

New x-ray phase contrast imaging techniques without using synchrotron radiation confront a common problem from the negative effects of finite source size and limited spatial resolution. These negative effects swamp the fine phase contrast fringes and make them almost undetectable. In order to alleviate this problem, deconvolution procedures should be applied to the blurred x-ray phase contrast images. In this study, three different deconvolution techniques, including Wiener filtering, Tikhonov regularization and Fourier-wavelet regularized deconvolution (ForWaRD), were applied to the simulated and experimental free space propagation x-ray phase contrast images of simple geometric phantoms. These algorithms were evaluated in terms of phase contrast improvement and signal-to-noise ratio. The results demonstrate that the ForWaRD algorithm is most appropriate for phase contrast image restoration among above-mentioned methods; it can effectively restore the lost information of phase contrast fringes while reduce the amplified noise during Fourier regularization.

Edge illumination x-ray phase contrast imaging (XPCI) provides increased contrast for low absorbing materials compared to attenuation images and sheds light on the material microstructure through dark field contrast. To apply XPCI in areas such as non-destructive testing and inline inspection, where scanned samples are increasingly compared to simulated reference images, accurate and efficient simulation software is required. However, currently available simulators rely on expensive Monte Carlo techniques or wave-optics frameworks, resulting in long simulation times. Furthermore, these simulators are often not optimized to work with computer-aided design (CAD) models, a common and memory-efficient method to represent manufactured objects, hindering their integration in an inspection pipeline. In this work, we address these shortcomings by introducing an edge illumination XPCI simulation framework built upon the recently developed CAD-ASTRA toolbox. CAD-ASTRA allows for the efficient simulation of x-ray projections from CAD models through GPU-accelerated ray tracing and supports ray refraction in a geometric optics framework. The edge illumination implementation is validated and its performance is benchmarked against GATE, a state-of-the-art Monte Carlo simulator, revealing a simulation speed increase of up to three orders of magnitude, while maintaining high accuracy in the resulting images.

Photon-counting computed tomography (PCCT) is a promising new technology with the potential to fundamentally change today's workflows in the daily routine and to provide new quantitative imaging information to improve clinical decision-making and patient management. The content of this review is based on an unrestricted literature search on PubMed and Google Scholar using the search terms "Photon-Counting CT", "Photon-Counting detector", "spectral CT", "Computed Tomography" as well as on the authors' experience. The fundamental difference with respect to the currently established energy-integrating CT detectors is that PCCT allows counting of every single photon at the detector level. Based on the identified literature, PCCT phantom measurements and initial clinical studies have demonstrated that the new technology allows improved spatial resolution, reduced image noise, and new possibilities for advanced quantitative image postprocessing. For clinical practice, the potential benefits include fewer beam hardening artifacts, radiation dose reduction, and the use of new contrast agents. In this review, we will discuss basic technical principles and potential clinical benefits and demonstrate first clinical use cases. · Photon-counting computed tomography (PCCT) has been implemented in the clinical routine. · Compared to energy-integrating detector CT, PCCT allows the reduction of electronic image noise. · PCCT provides increased spatial resolution and a higher contrast-to-noise ratio. · The novel detector technology allows the quantification of spectral information. · Stein T, Rau A, Russe MF et al. Photon-Counting Computed Tomography - Basic Principles, Potenzial Benefits, and Initial Clinical Experience. Fortschr Röntgenstr 2023; 195: 691 - 698.

The design and performance are described of a low-power copper-target X-ray tube with an elongated focus foreshortened to a diameter between 10 and 20 µm. The tube is designed for use with a specularly reflecting ellipsoidal mirror placed between 10 and 20 mm from the source and focusing the X-rays onto the sample, which may be 600 mm distant. The design maximizes the solid angle of collection of the emitted X-rays and thus achieves a high intensity at the sample. The electron beam, of circular cross section, from the gun is focused by an axial magnetic lens and then drawn out by a quadrupole lens to form an elongated spot on the target which is viewed at a small take-off angle. The limits imposed on the maximum intensity at the specimen by aberrations in the lens and by the permissible power dissipation in the target are discussed. The observed intensity is in reasonable agreement with the calculated intensity; it is comparable with that achieved with nonfocusing X-ray optics used with conventional X-ray tubes operated at a power more than 100 times as great.

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

Spectral X-ray phase contrast imaging with a CdTe photon-counting detector

A microfocus x-ray tube that can generate x rays with the focal spot size less than 5μm has been demonstrated using carbon nanotube (CNT) field emitters. A CNT cathode on a sharp tungsten tip, a magnetic solenoid lens, and a transmission-type x-ray target were adopted for the microfocus x-ray tube. The design characteristics and the operation performance of the microfocus x-ray tube are presented. Due to the small focal spot size, clear x-ray radiographic images of 6μm bars and x-ray images with the magnification factor of higher than 230 were obtained.

OA248] Computer-based platform for phase contrast breast imaging

Reusing industrial waste materials is vital for environmental conservation and sustainability, with concrete playing a significant role in recycling efforts and air purification. This paper proposes an efficient hybrid technique for developing LWSCC incorporating waste-expanded polystyrene (EPS). The proposed hybrid method is the joint execution of the war strategy optimisation (WSO) and tree hierarchical deep convolutional neural network (THDCNN). It is commonly referred to as the WSO-THDCNN approach. The primary aim is to enhance the hardening properties of LWSCC while minimising errors in material composition. WSO optimises the concrete mix by maximising the use of recycled EPS waste, while THDCNN predicts the material behaviour and structural characteristics. The method is implemented on the MATLAB platform, yielding superior outcomes compared to existing systems such as the Deep Neural Network (DNN) the Firefly Optimization Algorithm-Radial Basis Function Neural Network (FOA-RBFNN) and the Support Vector Machine (SVM). The accuracy of the existing methods is recorded at 0.780, 0.990 and 0.850, whereas the proposed technique achieves an impressive accuracy of 0.995. Furthermore, it displays a Root Mean Square Error (RMSE) of 3.549 and an Average Relative Error (ARE) of 5.43, demonstrating its effectiveness and reliability in improving LWSCC properties.