X-ray Computed Tomography Research Articles

High Power Laser Cutting of SiC-Al2O3 Ceramic Matrix Composites

Machining composite to achieve the desired surface and sub-surface condition, whether through conventional or non-conventional techniques, presents persistent challenges due to their anisotropic thermal characteristics. These challenges escalate when dealing with ceramic matrix composites (CMC) due to their high melting and boiling temperature. This study investigates the surface and sub-surface characteristics of SiC-Al2O3 CMC laser-cut components, produced using a 2 kW quasi-continuous wave laser. The influence of laser parameters such as focal position, cutting speed, number of cutting passes, average power, and assist gas type on surface and sub-surface characteristics have been investigated in detail. The laser cut samples were analysed using white light interferometer, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX) and 3D X-ray Computer Tomography (XCT) for both surface and sub-surface characteristics. The effect of laser process parameters on the surface composition, surface topology, and sub-surface thermal defects have been studied in detail. The results revealed that multi-pass cutting (16 pass) can be used to achieve lower thermal affected zone (~200 µm) and reduced surface roughness with an overall cutting speed of 625 mm/min. No delamination was observed with multi-pass cutting. Nitrogen was found to be the most suitable assist gas, as it prevented oxide layer formation across the laser cut SiC-Al2O3 CMC surface.

Characterization of Kinetics-Controlled Morphologies in the Growth of Silver Crystals from a Primary Lead Melt

Silver, a precious metal, can be recovered as a by-product of the processing of non-ferrous metals such as lead. In this work, silver crystals grown from the controlled cooling of a 10% silver–90% lead melt have been examined to quantify crystal morphologies developed under industrial conditions. X-ray tomography (XCT) is adapted to quantify the size and morphology of silver crystal structures grown from the Ag-Pb melt. The examination utilized high X-ray energies and small sample sizes to mitigate attenuation and enhance image quality. Examination of single crystal dendrites under high magnification demonstrates that silver crystals, even those grown under commercial conditions, yield a Face-Centered Cubic (FCC) crystalline lattice, which could be important for the practical extension of this work to the commercial production of Ag nano-crystals and crystalline supra-molecular structures. The crystals observed are composed of multiple twinned euhedral grains in a variety of dendritic to acicular arrangements, yielding a substantial heterogeneity of crystalline forms. XCT data were used to generate size and shape descriptors for the individual crystals. The results were compared to an equivalent set of descriptors generated from laser sizing examination of a sample of unconsolidated crystals from the same experimental run. The correspondence to within 9% of the crystal equivalent diameters determined independently by the XCT and laser sizing demonstrates a favorable outcome in particle sizing as achieved by visual inspection of XCT results. XCT examination of crystal assemblages identifies small octahedral crystals and larger triangular platelets. The structures expected for FCC crystals grown at thermodynamically controlled conditions are not observed in our systems, suggesting the possibility of the first crystal nuclei form at such conditions, but their growth transition to kinetically controlled mechanisms occurs as their size increases above a threshold cutoff. Based on literature observations, this size threshold is much smaller than the resolution of the XCT instrumentation employed herein. Our characterization data are in fact consistent with thermodynamics/kinetics—and then kinetics-controlled mechanisms—as the crystal size increases. This observation is important because the systems considered here are representative of commercial processes. As such, this work extends prior crystal growth concepts, which were explored in aqueous systems often probed by electrodeposition.

Improving the meso-structure identification of asphalt mixture using combined neutron and X-ray imaging

The accurate characterization of the internal structure of asphalt mixture is significant to understand its mechanical behavior. Combining imaging with neutrons and X-rays is beneficial for investigations of asphalt mixture meso-structure as their different attenuation coefficients for the main components of the asphalt mixture. To compensate for the shortcomings of only using X-ray imaging to identify asphalt mixture meso-structure, this study aims to improve the identification of the meso-structure of asphalt mixture using the complementarity of neutron and X-ray tomography. Due to the lack of experience in using neutron imaging to test the asphalt mixture meso-structure, this paper studied the influencing factors of neutron imaging test on asphalt mixture. To obtain the fusion image, a registration method of the neutron image and X-ray image and an acquisition method of fusion image were proposed. The volume fractions and area fractions of three phases (air voids, aggregates and mortar) obtained from the fusion images were compared with those obtained from neutron and X-ray images. The proposed method was validated by comparing the volume fractions computed from images and the actual values. These efforts contribute to improving the identification of the internal meso-structure of asphalt mixture.

Three-Dimensional Observation of Swelling Behavior of Water-Absorbing Fibers Using X-ray CT

Three-Dimensional Observation of Swelling Behavior of Water-Absorbing Fibers Using X-ray CT

Single-Subject Deep-Learning Image Reconstruction With a Neural Optimization Transfer Algorithm for PET-Enabled Dual-Energy CT Imaging.

Combining dual-energy computed tomography (DECT) with positron emission tomography (PET) offers many potential clinical applications but typically requires expensive hardware upgrades or increases radiation doses on PET/CT scanners due to an extra X-ray CT scan. The recent PET-enabled DECT method allows DECT imaging on PET/CT without requiring a second X-ray CT scan. It combines the already existing X-ray CT image with a 511 keV γ -ray CT (gCT) image reconstructed from time-of-flight PET emission data. A kernelized framework has been developed for reconstructing gCT image but this method has not fully exploited the potential of prior knowledge. Use of deep neural networks may explore the power of deep learning in this application. However, common approaches require a large database for training, which is impractical for a new imaging method like PET-enabled DECT. Here, we propose a single-subject method by using neural-network representation as a deep coefficient prior to improving gCT image reconstruction without population-based pre-training. The resulting optimization problem becomes the tomographic estimation of nonlinear neural-network parameters from gCT projection data. This complicated problem can be efficiently solved by utilizing the optimization transfer strategy with quadratic surrogates. Each iteration of the proposed neural optimization transfer algorithm includes: PET activity image update; gCT image update; and least-square neural-network learning in the gCT image domain. This algorithm is guaranteed to monotonically increase the data likelihood. Results from computer simulation, real phantom data and real patient data have demonstrated that the proposed method can significantly improve gCT image quality and consequent multi-material decomposition as compared to other methods.

Characterisation of the heterogeneity of a sand specimen in triaxial compression using x-ray CT and representative elementary volumes

Standard laboratory tests, such as the triaxial test, are often considered to be element tests. But, when observing such a test, it becomes obvious that this assumption of homogeneity is far from accurate. The localisation of strain is often visible to the naked eye and becomes even more obvious when observed on the grain scale. Other variables, such as those describing the soil fabric, are expected to localise as well. In this work, two sand samples are analysed at different loading states regarding the heterogeneity of three soil variables: void ratio, coordination number and contact orientation anisotropy. For this purpose, the size of a Representative Elementary Volume (REV) is determined using three criteria: the convergence of the mean and variance of the variables with increasing element size as well as a χ2-test. The size of the REV is varying depending on the chosen variable but almost the same for the two specimens when related to the mean grain diameter d50. The REV is placed in a regular grid throughout the specimen and the three variables are determined for each REV. The stochastic as well as spatial heterogeneity is identified for each specimen. As one of the samples is analysed for different loading states throughout a triaxial test, the evolution of the soil heterogeneity is identified. A localisation of all three variables can be observed at the end of the triaxial test as well as a strong initial heterogeneity for both sand samples.

About the influence of high temperature or fire testing conditions on the tensile behavior of carbon reinforced poly phenylene sulfide laminates

This study aims to investigate the thermo-mechanical coupling in carbon fibers reinforced Poly Phenylene Sulfide (PPS) laminates subjected to critical temperature conditions. In order to dissociate the physical phenomena (degradation/decomposition on the one hand and deformation/damage mechanisms on the other hand) at play in quasi-isotropic laminates (fiber-dominated mechanical behavior), homogenous and fire testing conditions (heterogenous) were considered with or without mechanical loading. X-Ray tomographic and fractographic analyses were conducted to identify the role played by porosities formation (resulting from thermally induced deformations and damages) on the structural bearing capabilities of C/PPS laminates to be used in high-temperature environments. Under high temperature conditions (homogenous temperature distribution), the retention of tensile properties is not well preserved as the axial stiffness and strength decrease of 50% and 75%, respectively. Under fire conditions (heterogenous temperature distribution), the degradation of tensile properties is more dramatic with an 80% decrease.

Successful coronary artery bypass surgery in an elderly patient with giant air cyst in the left lung

Lung air cysts and bullae are airborne cavities larger than 1 cm in diameter, surrounded by a thin wall, localized within the lung tissue. The bullae are often located apically in the lung. They are usually asymptomatic unless they are very large in size and are detected on chest X-ray or lung tomography. In this article, we present an asymptomatic 79-year-old male patient who was randomly detected as having an air cyst in the anterior segment of the upper lobe of the left lung during the preparation for coronary bypass. We did not find similar cases in PUBMED literature review.

Fast and Efficient Lung Abnormality Identification With Explainable AI: A Comprehensive Framework for Chest CT Scan and X-Ray Images

Fast and Efficient Lung Abnormality Identification With Explainable AI: A Comprehensive Framework for Chest CT Scan and X-Ray Images

Ультразвуковое исследование легких при диагностике пневмоний у детей

Aim. To present current data on the characterization, methodology, and use of lung ultrasound (LUS) in the diagnosis of pneumonia in children. Key points. Respiratory pathology is most common in childhood due to the peculiarities of immunity and structure of the respiratory tract. Pneumonia is a not uncommon disease of the lower respiratory tract in children, requiring quick, accurate and easy to perform diagnosis, as well as correct and timely treatment. Recently, lung ultrasound examination has been gaining popularity as a tool for diagnosing diseases of the lower respiratory tract, including pneumonias. It was widely used during the COVID-19 pandemic, when there were a lot of patients. The advantages of this method are the ease of the procedure, the speed of obtaining results, the absence of ionizing radiation and the non-invasiveness of the study. Ultrasound allows for a real-time assessment of the lung tissue lesion pattern. Also, an ultrasound examination lets the child stay with their mother and keep calm during the diagnostic procedure, preventing stress. Numerous trials demonstrated high specificity and sensitivity of this diagnostic method. Results of the common and more time-consuming diagnostic methods, such as lung CT and lung X-ray, have been compared with ultrasonographic results. With lung ultrasound, the possibility of dynamic patient monitoring is opened up without the fear of receiving unnecessary radiation exposure. The review presents data on the gaining popularity of LUS, its sensitivity and specificity, the technique of the study, as well as characteristic signs of pulmonary lesions in pneumonia. Conclusion. Lung ultrasound as a tool for pneumonia diagnostics is widely used abroad and has been included in pneumonia management protocols. Ease-of-use and safety for patients facilitate the introduction and application of this diagnostic method in paediatric inpatientunits; later, it can be used in outpatient settings as well. Multidisciplinary approach to the diagnosis of pneumonia contributes to the acceleration of the correct diagnosis and the beginning of adequate therapy. Keywords: lung ultrasound, pneumonia in children, ultrasound signs of pulmonary lesions.

Effect of academic-environmental stress on apical periodontitis of non-endodontic teeth

Abstract Background: The periapical area of a tooth was diagnosed using radiography; many types of risk factors can affect the health of the apical area which is the stress during life. Objective: To analyze the prevalence of academic-environmental stress and apical periodontitis in non-endodontic teeth of dental students using cone-beam computed tomography (CBCT) X-ray, and to demonstrate the association between stress and the prevalence of apical periodontitis. Materials and Methods: Cross-sectional study was done on the 103 recruited dental students aged 22–24 years during the final examination year of study in dentistry college. The academic-environmental stress scale was used to measure the level of stress in each student. The CBCT X-ray was taken for each student. The apical area was measured only for non-root canal-treated teeth using the CBCT periapical radiography index. Chi-square (χ 2) test was used to show the percentages of stress and the relationship between apical periodontitis and stress in students. Results: 53 students (51.5%) had a stressed state, whereas 50 students (48.5%) had a non-stressful state. The prevalence of apical periodontitis was greater among stressed than that of non-stressed students in non-endodontic teeth. Statistically, there was a significant relationship between academic-environmental stress and apical periodontitis in non-endodontic teeth. Conclusion: There was a negative effect of examination stress on the apical healthy of teeth that can be increased with the presence of any additional factors such as problems of life.

Sparse-view X-ray CT based on a box-constrained nonlinear weighted anisotropic TV regularization.

Sparse-view computed tomography (CT) is an important way to reduce the negative effect of radiation exposure in medical imaging by skipping some X-ray projections. However, due to violating the Nyquist/Shannon sampling criterion, there are severe streaking artifacts in the reconstructed CT images that could mislead diagnosis. Noting the ill-posedness nature of the corresponding inverse problem in a sparse-view CT, minimizing an energy functional composed by an image fidelity term together with properly chosen regularization terms is widely used to reconstruct a medical meaningful attenuation image. In this paper, we propose a regularization, called the box-constrained nonlinear weighted anisotropic total variation (box-constrained NWATV), and minimize the regularization term accompanying the least square fitting using an alternative direction method of multipliers (ADMM) type method. The proposed method is validated through the Shepp-Logan phantom model, alongisde the actual walnut X-ray projections provided by Finnish Inverse Problems Society and the human lung images. The experimental results show that the reconstruction speed of the proposed method is significantly accelerated compared to the existing $ L_1/L_2 $ regularization method. Precisely, the central processing unit (CPU) time is reduced more than 8 times.

Study of the structure of fibrous composite material using computational x-ray tomography

the article discusses the determination of the actual porosity and the actual volumetric content of the reinforcing material and binder in a sample of fibrous polymer composite material (FPCM) using the non-destructive method of computational x-ray tomography. It is shown that the linear attenuation coefficient (LAC) of X-ray radiation in the volume of the sample under study based on the set of integral shadow projections obtained by X-ray transmission in various directions and its root-mean-square deviation (RMSD) provide sufficient information about the parameters of the microstructure of the sample under study. To obtain quantitative characteristics of porosity and volumetric content of components, it is necessary to examine test samples made from similar components with previously known various parameters of the material structure in the required range of scatter of these characteristics. The proposed method can be used as a non-destructive control of the structure parameters of critically important products made of VPCM, both in general and in selected local areas of the product. Also, this method is recommended for determining the actual porosity and the actual volumetric content of the binder when carrying out research work on the influence of VPCM structure parameters on the durability and residual strength of samples when exposed to external factors during operation, in particular when carrying out certification work on elementary samples.

Downsizing and soft X-ray tomography for cellular uptake of interpenetrated metal-organic frameworks.

Metal-organic frameworks (MOFs) are porous materials with potential in biomedical applications such as sensing, drug delivery, and radiosensitization. However, how to tune the properties of the MOFs for such applications remains challenging. Herein, we synthesized two MOFs, Zr-PEB and Hf-PEB. Zr-PEB can be classified as porous interpenetrated zirconium frameworks (PIZOFs) and Hf-PEB is its analogue. We controlled their sizes while maintaining their crystal structure by employing a coordination modulation strategy. They were designed to serve as sensitizer for X-ray therapy and as potential drug carriers. Comprehensive characterizations of the MOFs' properties have been conducted, and the in vitro biological impacts have been studied. Since viability assay showed that Hf-PEB was more biocompatible compared to Zr-PEB, the cellular uptake of Hf-PEB by cells was evaluated using both fluorescence microscopy and soft X-ray tomography (SXT), and the three-dimensional structure of Hf-PEB in cells was observed. The results revealed the potential of Zr-PEB and Hf-PEB as nanomaterials for biomedical applications and demonstrated that SXT is an effective tool to assist the development of such materials.

Collagen/polyester-polyurethane porous scaffolds for use in meniscal repair.

Focusing on the regeneration of damaged knee meniscus, we propose a hybrid scaffold made of poly(ester-urethane) (PEU) and collagen that combines suitable mechanical properties with enhanced biological integration. To ensure biocompatibility and degradability, the degradable PEU was prepared from a poly(ε-caprolactone), L-lysine diisocyanate prepolymer (PCL di-NCO) and poly(lactic-co-glycolic acid) diol (PLGA). The resulting PEU (Mn = 52 000 g mol-1) was used to prepare porous scaffolds using the solvent casting (SC)/particle leaching (PL) method at an optimized salt/PEU weight ratio of 5 : 1. The morphology, pore size and porosity of the scaffolds were evaluated by SEM showing interconnected pores with a uniform size of around 170 μm. Mechanical properties were found to be close to those of the human meniscus (Ey ∼ 0.6 MPa at 37 °C). To enhance the biological properties, incorporation of collagen type 1 (Col) was then performed via soaking, injection or forced infiltration. The latter yielded the best results as shown by SEM-EDX and X-ray tomography analyses that confirmed the morphology and highlighted the efficient pore Col-coating with an average of 0.3 wt% Col in the scaffolds. Finally, in vitro L929 cell assays confirmed higher cell proliferation and an improved cellular affinity towards the proposed scaffolds compared to culture plates and a gold standard commercial meniscal implant.

Nanocrystalline iron hydroxide lignocellulose filters for arsenate remediation.

Harmful levels of environmental contaminants, such as arsenic (As), persist readily in the environment, threatening safe drinking water supplies in many parts of the world. In this paper, we present a straightforward and cost-effective filtration technology for the removal of arsenate from potable water. Biocomposite filters comprised of nanocrystalline iron oxides or oxyhydroxides mineralized within lignocellulose scaffolds constitute a promising low cost, low-tech avenue for the removal of these contaminants. Two types of iron oxide mineral phases, 2-line ferrihydrite (Fh) and magnetite (Mt), were synthesized within highly porous balsa wood using an environmentally benign modification process and studied in view of their effective removal of As from contaminated water. The mineral deposition pattern, minerology, as well as crystallinity, were assessed using scanning electron microscopy, transmission electron microscopy, micro-computed X-ray tomography, confocal Raman microscopy, infrared spectroscopy, and X-ray powder diffraction. Our results indicate a preferential distribution of the Fh mineral phase within the micro-porous cell wall and radial parenchyma cells of rays, while Mt is formed primarily at the cell wall/lumen interface of vessels and fibers. Water samples of known As concentrations were subjected to composite filters in batch incubation and gravity-driven flow-through adsorption tests. Eluents were analyzed using microwave plasma optical emission spectroscopy (MP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). By subjecting the filters to a flow of contaminated water, the time for As uptake was reduced to minutes rather than hours, while immobilizing the same amount of As. The retention of As within the composite filter was further confirmed through energy-dispersive X-ray mappings. Apart from addressing dangerously high levels of arsenate in potable water, these versatile iron oxide lignocellulosic filters harbor tremendous potential for addressing current and emerging environmental contaminants that are known to adsorb on iron oxide mineral phases, such as phosphate, polycyclic aromatic hydrocarbons or heavy metals.

Inner product regularized multi-energy X-ray tomography for material decomposition

Inner product regularized multi-energy X-ray tomography for material decomposition

ВИНАХІД КОМП‘ЮТЕРНОЇ ТОМОГРАФІЇ І ЙОГО ЗНАЧЕННЯ В ІСТОРІЇ ПУЛЬМОНОЛОГІЇ

Imaging diagnostic methods in pulmonology originate from the discovery of X-rays. Radiography is the first-line tool for chest imaging, but in many cases its capabilities are limited. The aim was to study the history of the invention of computed tomography. Since the radiogram is a two-dimensional summation image of a three-dimensional anatomical structure, there was a need to visualize separate layers of the pathological process. Since 1913, many technical solutions of tomography have been tested. Linear tomography for some time served for the diagnosis of lung pathology, helped to determine the localization more accurately, examine a prevalence, nature and structure of the pathological process, to detect small pathological formations and cavities. But the quality of tomography was not satisfactory. The two outstanding inventors of computed tomography who were awarded the 1979 Nobel Prize in Medicine were not the physicians. Allan McLeod Cormack (Professor and Head of the Institute of Physics at Tufts University, Medford, Massachusetts, USA) was the first to outline the principles of cross-sectional tissue reconstruction in an organ based on X-ray projections in 1963. Godfrey Newbold Hounsfield (Head of Medical Research at Electric and Musical Industries, Middlesex, England) not only reproduced the mathematical algorithms of the technique, but also designed the tomograph and directly participated in its clinical implementation in 1971. Among the developers of the idea of three-dimensional X-ray tomography in 19571958 were the scientists of Kyiv Polytechnic Institute Semyon Tetelbaum and Boris Korenblyum. Key words: radiology, computed tomography, history of pulmonology.

The influence of biomedical engineering in India

This comprehensive analysis delves into various crucial facets of biomedical engineering, covering cutting-edge technologies, creative methodologies, and ethical dilemmas. Quality Management Systems (QMS) play a pivotal role in maintaining precision, safety, and efficacy in lab experiments and biomedical product development, ensuring adherence to strict quality standards through guidelines like Good Laboratory Practice (GLP) and Good Manufacturing Practice (GMP). Advancements in medical imaging, from X-ray CT to molecular imaging, are revolutionizing disease diagnosis and treatment across multiple medical fields. Biomaterials and tissue engineering hold immense potential in regenerative medicine, addressing challenges like immune rejection and implant wear to meet diverse healthcare needs. Biomechanics and rehabilitation engineering merge biomechanical principles with assistive technologies to empower individuals with disabilities and improve their daily autonomy. Biomedical sensors, devices, and nanotechnology are driving personalized healthcare solutions, enhancing disease management through wearable and implantable technologies. Regulatory policies in India underscore the importance of strict regulations for medical devices and therapeutics to ensure safety and efficacy. Overall, this review highlights the transformative impact of biomedical engineering on healthcare advancements and societal well-being through responsible innovation and ethical practices.

Super-Resolution in Low Dose X-ray CT via Focal Spot Mitigation With Generative Diffusion Networks

Super-Resolution in Low Dose X-ray CT via Focal Spot Mitigation With Generative Diffusion Networks