Internal Structure Of Object Research Articles

A Geant4-based Monte Carlo X-ray imaging simulation platform

X-ray digital radiography plays a pivotal role in accessing the internal structure of objects. Nevertheless, key imaging parameters, such as source-to-target distance or number of projected images needed for three-dimensional construction, mostly rely on real-life trials thus increasing radiation exposure risks. This paper introduces a recently developed software platform known as GMAX (Geant4-based Monte Carlo Advanced X-ray) that helps addressing above issues from a simulation perspective. GMAX employs Geant4, a Monte Carlo simulation code at its core and facilitates high-fidelity X-ray imaging, requiring no prior user experience. Compared to CAD models that only reflect object's geometrical information, GMAX simulates how objects interact with photon and can accurately evaluate important imaging parameters, such as target object to detector distance. It also provides three-dimensional construction functionality for images and therefore could be used as an effective tool for X-ray non-destructive testing and inspection.

Image fast reconstruction for sparse view computed tomography with reduced sampling integration time

Industrial computed tomography (CT) can detect the internal structure of objects nondestructively. Its scanning and image reconstruction are time-consuming, which limits its application in the fast detection field. In this work, we reduce the sampling integration time in sparse view CT to achieve ultra-fast scanning in only 5 s. However, this ultra-fast scanning method produces more noise and streak artifacts in the reconstructed CT images. The existing reconstruction methods cannot effectively reconstruct high quality CT images under this ultra-fast scanning. To solve this issue, a faster and higher quality CT image reconstruction method is proposed in this paper. We construct a novel objective function using multi-directional TV and adaptive non-local means (ANLM), and design a solution algorithm to solve the objective function. The multi-directional TV-norm takes into account the differences in horizontal, vertical, and 45° directional gradients to obtain more image detail information, while the ANLM-norm focuses on noise suppression. Simulation and practical experiments show that the proposed method can reconstruct higher quality CT images under faster CT scanning strategy, and the peak signal to noise ratio (PSNR) is 1.3 dB higher than the optimal baseline algorithm. On the other hand, our method converges faster and achieves a shorter CT image reconstruction time, which is 47 s shorter than the current popular iterative reconstruction methods. This reconstruction method provides a reliable scheme for faster CT scanning and image reconstruction.

Analysis of visualization through depolarization via light scattering related to surface structure in visible and infrared light

Among the various factors of polarization changes due to surface and internal structures of objects, the phenomenon of depolarization through light scattering is one of the most commonly occurring factors in visualization through polarization imaging. In the present study, depolarization due to surface light scattering over a broad wavelength range from the visible to IR regions was experimentally and theoretically elucidated. Using the polarization-probe-polarization-imaging system, we achieved successful visualization of depolarization based on surface structure differences at the nano-level while observing the instrument dial. The results of electromagnetic field analysis using the finite-difference time-domain method, incorporating surface structures observed through microscopic observation, revealed that Rayleigh scattering on the nano-scale uneven surface extends beyond depolarization.

Improving the spatial resolution of electrical impedance tomography using logical operation as post-processing

Abstract Electrical impedance tomography is a nondestructive tomographic technique used to estimate the internal structures of objects. Obtaining a tomograph image is synonymous with solving an inverse problem. Since the inverse problem is ill-posed, the obtained solution contains errors, resulting in degradation of the spatial resolution. This paper proposes a post-processing method to improve the spatial resolution. In the post-process, two tomograph images obtained using different solving parameters were logically combined. By combining tomograph images obtained with different hyperparameters and current injection patterns, the spatial resolutions regarding the position and size of foreign objects were improved.

The Impact of Serpentinization on the Initial Conditions of Satellite Forming Collisions of Large Kuiper Belt Objects

Kuiper Belt objects are thought to be formed at least a few million years after the formation of calcium–aluminum-rich inclusions (CAIs), at a time when the 26Al isotope—the major source of radiogenic heat in the early solar system—had significantly depleted. The internal structure of these objects is highly dependent on any additional source that can produce extra heat in addition to that produced by the remaining, long-lasting radioactive isotopes. In this paper, we explore how serpentinization, the hydration of silicate minerals, can contribute to the heat budget and to what extent it can modify the internal structure of large Kuiper Belt objects. We find that the extent of restructuring depends very strongly on the start time of the formation process, the size of the object, and the starting ice-to-rock ratio. Serpentinization is able to restructure most of the interior of all objects in the whole size range (400–1200 km) and ice-to-rock ratio range investigated if the process starts early, ∼3 Myr after CAI formation, potentially leading to a predominantly serpentine core much earlier than previously thought (≤5 Myr versus several tens of million years). While the ratio of serpentinized material gradually decreases with the increasing formation time, the increasing ice-to-rock ratio, and the increasing start time of planetesimal formation in the outer solar system, in the case of the largest objects a significant part of the interior will be serpentinized even if the formation starts relatively late, ∼5 Myr after CAI formation. Therefore it is feasible that the interior of planetesimals may have contained a significant amount of serpentine, and in some cases, it could have been a dominant constituent, at the time of satellite-forming impacts.

Sinogram Upsampling via Sub-Riemannian Diffusion with Adaptive Weighting

Computed tomography is a versatile imaging technique used to enable seeing internal structures of objects without opening or destroying them. This is possible through a process called tomographic reconstruction, which reconstructs images from projections of the object that are obtained by penetrating the object with beams of radiation, such as X-rays, from different angles. These projection data are often limited to low-resolution data in terms of projection angles. These limited or subsampled data make it difficult to obtain high-quality reconstruction results. Hence, upsampling projection data is necessary. In this paper, we propose a sinogram upsampling method via the sub-Riemannian diffusion process. We first lift the data into a feature space, and we fill in the missing angle parts by propagating information from the observed data to the missing parts. We observe that the sinogram with limited angle data has high directional dependency, and based on this observation, we suggest an adaptive weighting scheme to keep information propagating toward the missing regions. This adaptive weighting allows for diffusing toward the desired directions. The experimental results show the effectiveness of the proposed method in some scenarios regarding inpainting fine details, when compared to the existing model-based methods, such as Plug-and-Play and total generalized variation.

High-speed X-ray radiography for experiments in impact dynamics using high-power X-ray tube, cesium iodine scintillator and laboratory optical camera

X-ray radiography and computed tomography have become well-established methods for investigation of internal structure of objects and for defectoscopy. Recently, the methods have even been used for in-situ analysis of materials under mechanical loading. Although the techniques would be very suitable for analysis during dynamic events, their application is constrained by typical achievable frame rates. Therefore, fast imaging is usually limited to facilities providing sufficient flux like particle accelerators. In this paper, we test imaging performance of a laboratory-based setup with a high-power X-ray tube, a scintillation panel, and an optical camera. Fast-rotating object and typical specimens for impact testing are irradiated with different power settings and quality of captured images is evaluated and analyzed. It is found out that the system can be successfully used for imaging at several hundred frames per second allowing for inspection of slow impact dynamics experiments.

RECOMMENDED TECHNOLOGY FOR TOMOGRAPHIC INSPECTION IN THE LABORATORY

Paper presents a detailed technology of tomographic inspection in the laboratory. Tomographic inspection is a powerful tool for obtaining high-quality three-dimensional images of the internal structure of objects. The advantages of the method are considered, which include the non-destructive nature of the control, high resolution, measurement accuracy, and the ability to detect defects invisible to the human eye. The main attention is paid to the description of the main stages of tomographic inspection, which are recommended to achieve maximum efficiency. Possible errors that may occur during tomographic inspection in the laboratory are highlighted, and ways to eliminate them are provided. The optimal parameters that should be taken into account during tomographic inspection are considered, including the correct choice of tomograph parameters, setting of lighting conditions, and correct positioning of the object under inspection. The process of processing the obtained inspection data is described in detail, which helps to ensure high-quality information analysis. The authors also analyze the feasibility of the control stages, comparing the results obtained at different stages and considering their impact on the final result. This work is a valuable source of information for specialists involved in tomographic control in the laboratory. The described technology and recommendations will help to improve the quality and efficiency of tomographic inspection in their work. The research results presented in this article can improve the inspection process, reduce errors, and detect even the smallest defects in samples. In general, this paper offers a recommended technology for tomographic inspection in the laboratory, taking into account key aspects such as the advantages of the method, inspection stages, error elimination, optimal parameters, object positioning, and data processing. Taking these recommendations into account, specialists will be able to provide more accurate, efficient and reliable tomographic control in their work. Thus, this article will be a valuable addition to the scientific literature in the field of non-destructive testing, will help improve the quality of tomographic testing and promote the development of this important method in the laboratory.

Structure-aware guided filtering for a ring artifact correction in synchrotron x-ray microtomography.

Synchrotron-based x-ray microtomography (S-µCT) is a powerful non-invasive three-dimensional (3D) imaging technique used for visualizing the internal structure of objects with micron-scale spatial resolution. However, in practical applications, ring artifacts often occur in S-µCT, which significantly degrades image quality and hinders interpretation. In this study, we propose a ring artifact correction method based on guided image filtering (GIF). The method first extracts structural prior from the input S-µCT images and then uses it as the guidance image to correct the ring artifacts. Finally, GIF with a self-guidance image is employed to further enhance image quality. Extensive comparisons and analyses on simulations and real data experiments demonstrate that the proposed method is capable of effectively correcting ring artifacts, accompanied by low-dose noise suppression and sparse-view artifact reduction. These findings suggest that the proposed method has great potential to promote the wider applications of S-µCT in the future.

Angular X-ray transmission measurements of gold absorption gratings: comparison of different laboratory X-ray sources

Over the past few years, numerous advances have been made in X-ray imaging technology. X-ray imaging plays an important role in the non-destructive exploration of the internal structures of objects for research, medical and industrial applications. When X-rays are used in computed tomography (CT), the differences in density of various components of a specimen result in different degrees of absorption of the X-rays and are ultimately responsible for image formation and image contrast. However, in some situations, this contrast is not sufficient for the sample, e.g. in the case of fossils embedded in rock, there are often situations where the fossil and rock have similar grey values. Poor contrast causes the loss of valuable detail and makes further image processing steps such as segmentation challenging. There is a continuous need to improve and develop new image acquisition techniques with the goal to improve the quality of the obtained CT data. Computed tomography techniques have been extended to phase contrast imaging in recent years using the principle of Talbot-Lau interferometers. Initially performed in synchrotron facilities the method was extended to work with incoherent polychromatic X-ray sources by introducing a source grating into the setup and therefore reducing the requirements on the spatial coherence of the source significantly. In this work, we report on the experimental characterization of gold absorption gratings used in such a laboratory-based cone-beam phase contrast setup. The gold gratings are characterized by Angular X-ray Transmission using different laboratory X-ray sources, providing insights not only into the grating feature sizes but also validating the suitability of the available laboratory source for phase contrast imaging. This work is the first step in a project implementing phase contrast X-ray imaging in laboratory setups in South Africa.

Machine learning for detection of 3D features using sparse x-ray tomographic reconstruction.

In many inertial confinement fusion (ICF) experiments, the neutron yield and other parameters cannot be completely accounted for with one and two dimensional models. This discrepancy suggests that there are three dimensional effects that may be significant. Sources of these effects include defects in the shells and defects in shell interfaces, the fill tube of the capsule, and the joint feature in double shell targets. Due to their ability to penetrate materials, x rays are used to capture the internal structure of objects. Methods such as computational tomography use x-ray radiographs from hundreds of projections, in order to reconstruct a three dimensional model of the object. In experimental environments, such as the National Ignition Facility and Omega-60, the availability of these views is scarce, and in many cases only consists of a single line of sight. Mathematical reconstruction of a 3D object from sparse views is an ill-posed inverse problem. These types of problems are typically solved by utilizing prior information. Neural networks have been used for the task of 3D reconstruction as they are capable of encoding and leveraging this prior information. We utilize half a dozen, different convolutional neural networks to produce different 3D representations of ICF implosions from the experimental data. Deep supervision is utilized to train a neural network to produce high-resolution reconstructions. These representations are used to track 3D features of the capsules, such as the ablator, inner shell, and the joint between shell hemispheres. Machine learning, supplemented by different priors, is a promising method for 3D reconstructions in ICF and x-ray radiography, in general.

Application of digital processing methods for automated cardiac segmentation from computed tomography data

Computed tomography is now widely used in cardiac surgery as a method of non-destructive study of internal structure of objects, including specific tasks, such as mathematical modeling of physiological processes, surgical interventions in augmented reality, 3D printing, and radiomics. One of the key steps in creating a 3D model from computed tomography data is segmentation the process of selecting objects in the image. Currently, there are several approaches to automating the segmentation process, including image processing methods, texture analysis and machine learning algorithms (in particular, clustering). Image processing methods are the simplest of the presented approaches and are found in various applications for segmentation of tomographic data. This paper reviews the advantages and disadvantages of various image processing methods (threshold, region growing, contour detection, and morphological watersheds) as tools for automated cardiac segmentation from computed tomography data. It was revealed that computed tomography images have characteristic features affecting the segmentation process (presence of noise, partial volume effect, etc.). The choice of the segmentation method is based on the brightness characteristics of the area of interest and also requires knowledge of the subject area, so it should be performed by a specialist with competence in anatomy and digital image processing. As independent methods of automated segmentation, the listed methods are applicable only in relatively simple cases (selection of homogeneous or high-contrast areas), otherwise, a combination of these methods, the use of machine learning algorithms or manual correction of the results is required.

Method for virtual optical sectioning and tomography utilizing shallow depth of field.

A method is proposed for high-resolution, three-dimensional reconstruction of internal structures of objects from planar transmission images. The described approach can be used with any form of radiation or matter waves, in principle, provided that the depth of field is smaller than the thickness of the sample. The physical optics basis for the method is elucidated, and the reconstruction algorithm is presented in detail. A simulated example demonstrates an application of the method to three-dimensional electron transmission imaging of a nanoparticle under realistic radiation dose and spatial resolution constraints. It is envisaged that the method can be applicable in high-resolution transmission electron microscopy, soft x-ray microscopy, ultrasound imaging, and other areas.

Projection Image Interpolation for 4DCT Data using Optical Flow

Recent progress in additive manufacturing (AM) technology has made it possible to form objects with fine and complex internal structures. X-ray computed tomography (CT) is widely used for inspecting AM objects because it can scan objects’ internal structures nondestructively. Although conventional X-ray CT scanning scans static objects to obtain their three-dimensional geometry, recently, attention has been paid to scanning deforming objects in real time and obtaining time-varying fourdimensional (4D) data. This technology, called 4-dimensional computed tomography, is also used to conduct load-bearing tests of AM products and observation of the deformation of the internal structure of objects. However, dynamic deformation of an object to be scanned while rotating 360° yields a series (one frame) of projection images necessary to reconstruct a CT volume, causing blurs in the reconstructed data. Therefore, we propose an algorithm to generate a frame of projection images of an arbitrary time point by interpolating the projection images from the previous and next frames of continuous scanning. Specifically, we generate the projection images from given frames using optical flow, which adopts the vector field of the gradient of projection values. This algorithm was applied to dynamically changing projection images to experimentally show its robustness against dynamical changes.

A Terahertz 3-D Imaging Method for Complex Internal Structure of Object

Terahertz (THz) technology is a promising technology in recent years due to its great potential for non-destructive testing (NDT) of specific materials. This article proposes a THz 3-D imaging method for the internal structure of materials, which is widely needed in NDT applications. First, a “rotating arrays” method for THz scanning is proposed. With rotating the conventional 2-D arrays, the “rotating arrays” method solves the problem that THz reflected waves from complex structures are hardly received by the probe. After that, a “two-step reconstruction” (TSR) THz data processing method is proposed. The first step is the “primary reconstruction” (PR), in which the sample is reconstructed without considering the refractive index of itself. Then, “secondary reconstruction” (SR) is used for refraction correction of the internal structure based on the refractive index of the material and the data obtained in the PR. The experimental results verify that compared with the conventional THz imaging method, the method proposed in this article can image the interfaces, air gaps, and complex geometric structures inside the measured object with satisfactory accuracy and can image the overall internal structure in 3-D.

X-ray source translation based computed tomography (STCT).

Micro computed tomography (µCT) allows the noninvasive visualization and 3D reconstruction of internal structures of objects with high resolution. However, the current commercial µCT system relatively rotates the source-detector or objects to collect projections, referred as RCT in this paper, and has difficulties in imaging large objects with high resolutions because fabrication of large-area, inexpensive flat-panel detectors remains a challenge. In this paper, we proposed a source translation based CT (STCT) for imaging large objects with high resolution to get rid of the limitation of the detector size, where the field of view is primarily determined by the source translation distance. To compensate for the deficiency of incomplete data in STCT, we introduced multi-scanning STCT (mSTCT), from which the projections theoretically meet the conditions required for accurate reconstructions. Theoretical and numerical studies showed that mSTCT has the ability to accurately image large objects without any visible artifacts. Numerical simulations also indicated that mSTCT has a potential capability to precisely image the region of interest (ROI) inside objects, which remains a challenge in RCT due to truncated projections. In addition, an experimental platform for mSTCT has been established, from which the 2D and 3D reconstructed results demonstrated its feasibility for µCT applications. Moreover, STCT also has a great potential for security inspection and product screening by using two perpendicular STCTs, with advantages of low-cost equipment and high-speed examination.

Fiber identification of braided composites using micro-computed tomography

Braided composites contain interwoven fibers that are embedded in a matrix material. Advanced measurement methods are required to accurately measure and characterize braided composites due to their interwoven composition. Micro-computed tomography (μCT) is an X-ray based measurement method that allows for the internal structure of objects to be examined. High-resolution μCT of braided composites allows for their internal geometry to be accurately measured. Braid samples were measured with a voxel size of 1.0 μm3, which resulted in a field of view of 4.904 x 4.904 x 3.064 mm3. With this field of view, individual fibers within the braid yarns could be identified and measured. The scientific visualization software package Avizo and the XFiber extension was used to identify and measure braid yarn fibers from the collected μCT measurements. Fiber properties such as orientation angles (φ and θ), curved fiber length, tortuosity, and fiber diameter were obtained. Additionally, finite element mesh geometries of the braid yarns within a braided structure were created. The presented methodology provides a roadmap for the accurate modeling of braided composite unit cell geometries using high-resolution μCT data.

Principles of Different X-ray Phase-Contrast Imaging: A Review

Numerous advances have been made in X-ray technology in recent years. X-ray imaging plays an important role in the nondestructive exploration of the internal structures of objects. However, the contrast of X-ray absorption images remains low, especially for materials with low atomic numbers, such as biological samples. X-ray phase-contrast images have an intrinsically higher contrast than absorption images. In this review, the principles, milestones, and recent progress of X-ray phase-contrast imaging methods are demonstrated. In addition, prospective applications are presented.

Modern Methods of Neutron Radiography and Tomography in Studies of the Internal Structure of Objects

The fundamentals, experimental possibilities, and applications of the methods of neutron radiography and tomography in studies of the structural features of large objects in various fields are reviewed. The main principles of neutron imaging are considered. Specialized experimental stations at the National Research Centre “Kurchatov Institute” and the Joint Institute for Nuclear Research are described, and their main parameters are presented. The experimental capabilities of these neutron facilities, including methodological approaches to variation of the neutron radiographic contrast with neutron energy dispersion, are described. A detailed review of the scientific results obtained on neutron radiography and tomography facilities is presented; these results concern engineering and technological objects, internal structure of meteorites, paleontological samples, and cultural heritage objects.

Phase contrast imaging based on continuous-wave terahertz digital holography

Terahertz (THz) radiation, due to its unique propagation characters of low-energy, high-penetration, water-absorption, provides internal structure of objects and comprehensive biological information in phase contrast imaging. It has been applied in biomedical imaging, non-destructive testing, and other fields. As an important part of THz imaging technology, continuous-wave (CW) THz digital holography (TDH) is qualified as a non-invasive and whole-field phase contrast imaging method. In this paper, we review the development and status of off-axis and in-line TDH, including the recording and reconstruction theory, experimental setup, and reconstruction algorithms. The influence of existing THz sources and the reconstruction algorithms on resolution and fidelity of imaging are analyzed. And the development trend of TDH is prospected in the end.