X-ray Imaging Applications Research Articles

Extraction of medium-spatial-frequency interfacial waviness and inner structure from X-ray multilayers using the speckle scanning technique

In this work, quick imaging measurements at different X-ray penetration depths, including the total-reflection region and Bragg reflection angles, were used to characterize the X-ray multilayer inner structure. We then measured the interface replication factor, intrinsic layer growth, and layer inhomogeneity, as these medium-spatial-frequency structural parameters are worthy of attention for demanding X-ray imaging and focusing applications. We compared conventional analysis methods to the speckle scanning technique, as it provides important phase-contrast and dark-field information. The method proposed here remedies the limitations of conventional methods and affords the possibility of in-situ determination of complex buried layers, localized strain or defects, and other statistical anomalies.

Time-coded aperture for x-ray imaging

We describe a computational imaging system for x-ray tomography, where image capture and post-processing are co-designed to improve final image quality when relative motion of an experiment’s components during a single exposure causes motion blur. The idea is based on temporally encoding the motion during each exposure by fluttering the detector shutter open and closed with a known sequence for guaranteeing an invertible motion blur kernel. While generally applicable, we demonstrate our approach by simulating blurry data acquisition for transmission x-ray tomography and deblurring the reconstructed images. The results suggest that optimized pseudo-random binary time-coded apertures can yield successful reconstructions independent of the size of the blur kernel. This Letter is especially relevant to high-speed x-ray tomography applications where time-resolution is limited by the detector or available photon flux.

Application of X-ray tomography to assess fatigue structural changes in asphalt mixtures

Application of X-ray tomography to assess fatigue structural changes in asphalt mixtures

Digital 3d x-ray microtomographic scanners for electronic equipment testing

The article studies the operating procedures of an X-ray microtomographic scanner and the module of reconstruction and analysis 3D-image of a test sample in particular. An algorithm for 3D-image reconstruction based on image shadow projections and mathematical methods of the processing are described. Chapter 1 describes the basic principles of X-ray tomography and general procedures of the device developed. Chapters 2 and 3 are devoted to the problem of resources saving by the system during the X-ray tomography procedure, which is achieved by preprocessing of the initial shadow projections. Preprocessing includes background noise removing from the images, which reduces the amount of shadow projections in general and increases the efficiency of the group shadow projections compression. In conclusion, the main applications of X-ray tomography are presented.

Study on the mechanism of afterglow in CsI: Tl and the afterglow suppression in CsI: Tl, Eu

Although there are many new scintillators being developed recently, CsI: Tl is still a very efficient one among them. However it suffers from afterglow which limits application in high-speed x-ray imaging. In order to find out the mechanism of afterglow and the method to suppress afterglow in CsI: Tl, the theoretical model of perfect CsI, CsI: Tl and CsI: Tl, Eu are built by the software Material Studio. The total and partial density of states of these three models is calculated within the framework of generalized gradient approximation and ultra-soft pseudo-potential. The results indicate that the generation of afterglow in CsI: Tl is due to the impurity energy bands introduced by Tl. Moreover, co-doping CsI: Tl with Eu will introduce deeper impurity energy bands which can effectively scavenge the electrons trapped by the shallow impurity energy bands introduced by Tl, thus suppressing the afterglow in CsI: Tl.

Metal Halide Perovskite Nanosheet for X-ray High-Resolution Scintillation Imaging Screens.

Scintillators, which are capable of converting ionizing radiation into visible photons, are an integral part of medical, security, and commercial diagnostic technologies such as X-ray imaging, nuclear cameras, and computed tomography. Conventional scintillator fabrication typically involves high-temperature sintering, generating agglomerated powders or large bulk crystals, which pose major challenges for device integration and processability. On the other hand, colloidal quantum dot scintillators cannot be cast into compact solid films with the necessary thickness required for most X-ray applications. Here, we report the room-temperature synthesis of a colloidal scintillator comprising CsPbBr3 nanosheets of large concentration (up to 150 mg/mL). The CsPbBr3 colloid exhibits a light yield (∼21000 photons/MeV) higher than that of the commercially available Ce:LuAG single-crystal scintillator (∼18000 photons/MeV). Scintillators based on these nanosheets display both strong radioluminescence (RL) and long-term stability under X-ray illumination. Importantly, the colloidal scintillator can be readily cast into a uniform crack-free large-area film (8.5 × 8.5 cm2 in area) with the requisite thickness for high-resolution X-ray imaging applications. We showcase prototype applications of these high-quality scintillating films as X-ray imaging screens for a cellphone panel and a standard central processing unit chip. Our radiography prototype combines large-area processability with high resolution and a strong penetration ability to sheath materials, such as resin and silicon. We reveal an energy transfer process inside those stacked nanosheet solids that is responsible for their superb scintillation performance. Our findings demonstrate a large-area solution-processed scintillator of stable and efficient RL as a promising approach for low-cost radiography and X-ray imaging applications.

Improved spectroscopic performance in compound semiconductor detectors for high rate X-ray and gamma-ray imaging applications: A novel depth of interaction correction technique

In this paper results are presented for a novel charge loss correction algorithm that exploits the process of charge induction within compound semiconductor detectors. By detecting the residual induced signals in the pixels neighbouring an event, it is possible to correct for variation in the charge collection efficiency that occurs when high energy photons deposit charge at different depths in the detector. Results from 500μm pitch pixel detectors produced from both GaAs:Cr and high-flux-capable CdZnTe material readout using the STFC’s PIXIE ASIC are used to demonstrate the correction process across two different detector materials. The application of this depth of interaction correction results in a significant improvement in the FWHM of the 59.5 keV γ-ray photopeak in a 0.5 mm thick GaAs:Cr sensor from 14 keV to 4.7 keV. The application of the correction at the higher energy 122 keV γ-ray photopeak in a 2 mm thick CdZnTe detector also demonstrated an improvement from 4.0 keV to 2.7 keV.

Few-photon computed x-ray imaging

X-rays are a ubiquitous imaging modality in clinical diagnostics and industrial inspections, thanks to their high penetration power. Conventional transmission-based x-ray radiography or computed tomography systems collect approximately 103–104 counts per pixel to ensure sufficient signal to noise ratio. The recent development of energy sensitive photon counting detectors has made x-ray imaging at low photon fluxes possible. In this paper, we report a photon-counting scheme that records the time stamp of individual photons, which follows a negative binomial distribution, and demonstrate the reconstruction based on the few-photon statistics. The x-ray projection and tomography reconstruction from measurements of ∼16 photons per beam show potential for using photon counting detectors for dose-efficient x-ray imaging applications.

Improved Woodcock tracking on Monte Carlo simulations for medical applications

This paper presents a new variance reduction technique called super voxel Woodcock (SVW), which combines Woodcock tracking technique with the super voxel concept, used in computer graphics. It consists in grouping the voxels of the volume in a super voxel grid (pre-processing step) by associating to each of the super voxels a local value of the most attenuate medium which will later serve to the interaction distances sampling. SVW allows reducing the sampling of the particle path while a high-density material is present within the simulated phantom. In order to evaluate the performance of the SVW method compare to both standard and Woodcock tracking methods, algorithms were implemented within the same GPU MCS framework GGEMS. This method improves the performance of the standard Woodcock method by a factor of 4.5 and 4.3 for x-ray imaging application and intraoperative radiotherapy respectively. The proposed SVW method did not introduce any bias on the simulations.

Sub-nanosecond single line-of-sight (SLOS) x-ray imagers (invited).

A new generation of fast-gated x-ray framing cameras have been developed that are capable of capturing multiple frames along a single line-of-sight with 30 ps temporal resolution. The instruments are constructed by integrating pulse-dilation electron imaging with burst mode hybrid-complimentary metal-oxide-semiconductor sensors. Two such instruments have been developed, characterized, and fielded at the National Ignition Facility and the OMEGA laser. These instruments are particularly suited for advanced x-ray imaging applications in Inertial Confinement Fusion and High energy density experiments. Here, we discuss the system architecture and the techniques required for tuning the instruments to achieve optimal performance. Characterization results are also presented along with planned future improvements to the design.

Azadirachta indica influenced biosynthesis of super-paramagnetic iron-oxide nanoparticles and their applications in tannery water treatment and X-ray imaging

Super-paramagnetic iron-oxide nanoparticles (SPIONs) have been exploited from a very long time and are researched profoundly due to their unique properties. In this study, SPIONs were synthesized using environmentally accepted green synthesis process where Azadirachta indica leaf extract was used as one of the reducing agents along with basic metal precursors used in chemical processes. The synthesized SPIONs were characterised using microscopic analysis (SEM, TEM, and AFM), spectroscopic analysis (FT-IR, UV–Vis, XRD, Raman, and zeta potential), and magnetometry (SQUID). The SPIONs were then tested for its application in the removal of heavy metals from tannery waste water and also X-ray imaging.

Ptychographical intensity interferometry imaging with incoherent light.

Intensity interferometry (II), the landmark of the second-order correlation, enables very long baseline observations at optical wavelengths, providing imaging with microarcsecond resolution. However, the unreliability of traditional phase retrieval algorithms required to reconstruct images in II has hindered its development. We here develop a method that circumvents this challenge, which enables II to reliably image complex shaped objects. Instead of measuring the whole object, we measure it part by part with a probe moving in a ptychographic way: adjacent parts overlap with each other. A relevant algorithm is developed to reliably and rapidly recover the object in a few iterations. Moreover, we propose an approach to remove the requirement for a precise knowledge of the probe, providing an error-tolerance of more than 50% for the location of the probe in our experiments. Furthermore, we extend II to short distance scenarios, providing a lensless imaging method with incoherent light and paving a way towards applications in X-ray imaging.

Improved total-variation noise-reduction technique with gradient method using iteration counter and its application in medical diagnostic chest and abdominal X-ray imaging

The development of novel noise-reduction algorithms is one of the main research areas in the field of medical diagnostic X-ray imaging. The purpose of this study is to develop an improved total-variation (TV) noise-reduction technique using a gradient method that employs an iteration counter, and confirm its feasibility for applications in chest and abdominal X-ray imaging systems. We evaluated image qualities using contrast–to–noise ratio (CNR) and relative standard deviation (RSD) calculations with the proposed and conventional noise-reduction algorithms for both chest and abdominal X-ray images. The results of the quantitative CNR and RSD evaluations demonstrated the superiority of the proposed TV noise-reduction technique over other algorithms; in particular, the comparison between the conventional and proposed TV techniques revealed that the proposed method has improved noise-reduction characteristics in all cases. In conclusion, the results demonstrated that the improved TV noise-reduction technique with the gradient method using the iteration counter can be used to acquire images with a better quality than those of conventional algorithms. This can lead to lowering of the radiation dose in chest and abdominal X-ray imaging systems.

The dynamic micro computed tomography at SSRF

Synchrotron radiation micro-computed tomography (SR-μCT) is a critical technique for quantitative characterizing the 3D internal structure of samples, recently the dynamic SR-μCT has been attracting vast attention since it can evaluate the three-dimensional structure evolution of a sample. A dynamic μCT method, which is based on monochromatic beam, was developed at the X-ray Imaging and Biomedical Application Beamline at Shanghai Synchrotron Radiation Facility, by combining the compressed sensing based CT reconstruction algorithm and hardware upgrade. The monochromatic beam based method can achieve quantitative information, and lower dose than the white beam base method in which the lower energy beam is absorbed by the sample rather than contribute to the final imaging signal. The developed method is successfully used to investigate the compression of the air sac during respiration in a bell cricket, providing new knowledge for further research on the insect respiratory system.

A new measurement method of actual focal spot position of an x-ray tube using a high-precision carbon-interspaced grid

This study investigated the effectiveness of a new method for measuring the actual focal spot position of a diagnostic x-ray tube using a high-precision antiscatter grid and a digital x-ray detector in which grid magnification, which is directly related to the focal spot position, was determined from the Fourier spectrum of the acquired x-ray grid’s image. A systematic experiment was performed to demonstrate the viability of the proposed measurement method. The hardware system used in the experiment consisted of an x-ray tube run at 50 kVp and 1 mA, a flat-panel detector with a pixel size of 49.5 µm, and a high-precision carbon-interspaced grid with a strip density of 200 lines/inch. The results indicated that the focal spot of the x-ray tube (Jupiter 5000, Oxford Instruments) used in the experiment was located approximately 31.10 mm inside from the exit flange, well agreed with the nominal value of 31.05 mm, which demonstrates the viability of the proposed measurement method. Thus, the proposed method can be utilized for system’s performance optimization in many x-ray imaging applications.

Automating High-Precision X-Ray and Neutron Imaging Applications With Robotics

Los Alamos National Laboratory and the University of Texas at Austin recently implemented a robotically controlled nondestructive testing (NDT) system for X-ray and neutron imaging. This system is intended to address the need for accurate measurements for a variety of parts and, be able to track measurement geometry at every imaging location, and is designed for high-throughput applications. This system was deployed in a beam port at a nuclear research reactor and in an operational inspection X-ray bay. The nuclear research reactor system consisted of a precision industrial seven-axis robot, 1.1-MW TRIGA research reactor, and a scintillator-mirror-camera-based imaging system. The X-ray bay system incorporated the same robot, a 225-keV microfocus X-ray source, and a custom flat panel digital detector. The robotic positioning arm is programmable and allows imaging in multiple configurations, including planar, cylindrical, as well as other user defined geometries that provide enhanced engineering evaluation capability. The imaging acquisition device is coupled with the robot for automated image acquisition. The robot can achieve target positional repeatability within 17 $\mu \text{m}$ in the 3-D space. Flexible automation with nondestructive imaging saves costs, reduces dosage, adds imaging techniques, and achieves better quality results in less time. Specifics regarding the robotic system and imaging acquisition and evaluation processes are presented. This paper reviews the comprehensive testing and system evaluation to affirm the feasibility of robotic NDT, presents the system configuration, and reviews results for both X-ray and neutron radiography imaging applications. Note to Practitioners —While looking for ways to improve throughput and increase efficiency in nondestructive imaging applications, the NonDestructive Testing and Evaluation Group at the Los Alamos National Laboratory decided to take a look at automation opportunities. Digital radiography and computed tomography are time-consuming processes, making them ideal candidates for robotic solutions. Radiography applications often require several images to be acquired from different angles and a lot of time they have to be very precise so that the feature of interest is identifiable and the resulting image meets the client’s requirements. With the robot acting as the motion control system, the imaged part can be placed directly in the beam path and oriented in six degrees of freedom. The robot can achieve significantly higher levels of precision than a human and has the ability to adjust the part while the source is active. The system also reduces levels of radiation our staff is exposed to, as the robot is setup to handle radioactive and hazardous parts. Not only does the robot move parts more precisely and with higher resolution than humans, but it also adds additional flexibility in the type and nature of images that the lab can produce. Future work will involve using this system for advanced automated scans such as achieving evenly spaced views around a sphere autonomously, since this system has not yet been used for more advanced scans beyond helical scanning. A tightly linked feedback loop between the robot and imaging code in which the imaging code would autonomously communicate to the robot what additional views are needed to reduce imaging error can also be explored.

The application of x-ray, computed tomography, and magnetic resonance imaging on 22 pediatric Langerhans cell histiocytosis patients with long bone involvement: A retrospective analysis.

The studies focusing on x-ray, computed tomography (CT), and magnetic resonance imaging (MRI) in pediatric Langerhans cell histiocytosis (LCH) patients were still rare. Therefore, we aimed to evaluate the application of x-ray, CT, and MRI in pediatric LCH patients with long bone involvement.Total 22 pediatric LCH patients were included in this study. The diagnosis of LCH was confirmed by pathological examination. All patients were followed up for 3 years. X-ray, CT, or MRI was performed and the results were recorded for further analyses.Among 22 pediatric patients, x-ray (n = 20), CT (n = 18), or MRI (n = 12) were used to scan the lesion on long bones affected by LCH. Femurs (n = 13, 38.24%), tibia (n = 11, 32.35%), humerus (n = 5, 14.71%), and radius (n = 4, 11.76%) were the most frequently affected anatomic sites. Ovoid or round radiolucent lesions, aggressive periosteal reaction, and swelling of surrounding soft tissues were characteristic image of long bones on x-ray, CT, and MRI in pediatric LCH.Femurs, tibia, humerus, and radius were the most commonly affected long bones of pediatric LCH. The application of x-ray, CT, and MRI on long bones could help with the diagnosis of pediatric LCH.

Simulation of Single Grid-based Phase-contrast Digital Tomosynthesis (PC-DTS)

Digital tomosynthesis (DTS) is a geometric tomography technique by a limited-angle scan which has been popularly used in both medical and industrial X-ray imaging applications. However, conventional DTS remains limited by low contrast especially in imaging samples of low atomic number Z such as breast and cartilage tissues. In this work, we applied the recently proposed phase-contrast imaging (PCI) technique, the so-called single grid-based PCI, to DTS in attempt to overcome this limitation. PCI has superior soft-tissue imaging capability while DTS has improved image contrast. Combining the two techniques can therefore considerably improve the X-ray imaging performance. We developed a useful simulation platform for single grid-based phase-contrast DTS reconstruction and performed a systematic simulation using a three-dimensional (3D) numerical breast phantom. In the simulation, an X-ray grid having a lead strip density of 200 lines/inch was used and the DTS scan comprised 41 projections within an angle range of θ = ±40° at an X-ray energy of 25 keV. We successfully reconstructed DTS images of much improved contrast, compared to conventional DTS images, which demonstrates the viability of the proposed approach.

Characteristics of the CsI:Tl Scintillator Crystal for X-Ray Imaging Applications

Scintillators are high-density luminescent materials that convert X-rays to visible light. Thallium doped cesium iodide (CsI:Tl) scintillation materials are widely used as converters for X-rays into visible light, with very high conversion efficiency of 64.000 optical photons/MeV. CsI:Tl crystals are commercially available, but, the possibility of developing these crystals into different geometric shapes, meeting the need for coupling the photosensor and reducing cost, makes this material very attractive for scientific research. The objective of this work was to study the feasibility of using radiation sensors, scintillators type, developed for use in imaging systems for X-rays. In this paper, the CsI:Tl scintillator crystal with nominal concentration of the 10-3 M was grown by the vertical Bridgman technique. The imaging performance of CsI:Tl scintillator was studied as a function of the design type and thickness, since it interferes with the light scattering and, hence, the detection efficiency plus final image resolution. The result of the diffraction X-ray analysis in the grown crystals was consistent with the pattern of a face-centered cubic (fcc) crystal structure. Slices 25 × 2 × 3 mm3 (length, thickness, height) of the crystal and mini crystals of 1 × 2 × 3 mm3 (length, thickness, height) were used for comparison in the imaging systems for X-rays. With these crystals scintillators, images of undesirable elements, such as metals in food packaging, were obtained. One-dimensional array of photodiodes and the photosensor CCD (Coupled Charge Device) component were used. In order to determine the ideal thickness of the slices of the scintillator crystal CsI:Tl, Monte Carlo method was used.

3D fibre architecture of fibre-reinforced sand

The mechanical behaviour of fibre-reinforced sands is primarily governed by the three-dimensional fibre architecture within the sand matrix. In laboratory, the normal procedures for sample preparation of fibre-sand mixtures generally produce a distribution of fibre orientations with a preferential bedding orientation, generating strength anisotropy of the composite’s response under loading. While demonstrating the potential application of X-ray tomography to the analysis of fibre-reinforced soils, this paper provides for the first time a direct experimental description of the three-dimensional architecture of the fibres induced by the laboratory sample fabrication method. Miniature fibre reinforced sand samples were produced using two widely used laboratory sample fabrication techniques: the moist tamping and the moist vibration. It is shown that both laboratory fabrication methods create anisotropic fibre orientation with preferential sub-horizontal directions. The fibre orientation distribution does not seem to be affected by the concentration of fibres, at least for the fibre concentrations considered in this study and, for both fabrication methods, the fibre orientation distribution appears to be axisymmetric with respect to the vertical axis of the sample. The X-ray analysis also demonstrates the presence of an increased porosity in the fibre vicinity, which confirms the assumption of the “stolen void ratio” effect adopted in previous constitutive modelling. A fibre orientation distribution function is tested and a combined experimental and analytical method for fibre orientation determination is further validated.