X-ray Computed Tomography Research Articles

Effect of microstructural damage evolution on tensile strength of ultra-high performance concrete: A multiscale numerical scheme

This study aims to investigate the tensile behavior of ultra-high performance concrete (UHPC) using a multiscale modeling approach. A micromechanics-based finite-element method is employed to investigate the evolution of microstructural damage and its effect on the macroscopic tensile strength of UHPC. X-ray computed tomography (CT) techniques are used to create a realistic microstructural geometry, and the cohesive-zone models are adopted to quantify the microcrack growth rate and the overall mechanical properties of UHPC under tension. A stiffness-degradation parameter is introduced to explain the evolution of the material tensile behavior. Satisfactory agreements are achieved between the simulation results and the experimental data from the direct tensile tests. To demonstrate the capability of the proposed multiscale modeling framework, the influences of curing age and freeze–thaw cycles of UHPC materials are further taken into account. The proposed multiscale simulation scheme integrated with the x-ray CT techniques and cohesive-zone model can serve as an effective and reliable method to capture the nonlinear tensile responses of UHPC materials and structures.

Osteoporosis Assessment Using Bone Density Measurement in Hounsfield Units in the Femoral Native CT Cross-Section: A Comparison with Computed Tomography X-Ray Absorptiometry of the Hip

Background/Objectives: Bone mineral density (BMD) loss leads to osteoporosis, significantly increasing fracture risk in both the axial and peripheral skeleton. The extent to which it is possible to estimate the degree of osteoporosis in the hip by determining the density in Hounsfield Unit (HU) measurements derived from computed tomography (CT) scans and to calculate quantitative BMD and T values from the HU values should be examined. Methods: A total of 240 patients (mean age: 64.9 ± 13.1 years, BMI: 26.8 ± 6.8 kg/m2) underwent CT-based BMD assessments using CTXA-Hip. Subregions of the proximal femur, including the femoral head, femoral neck, and intertrochanteric region, were analyzed for cancellous density in HUs using circular and irregular region-of-interest (ROI) measurements. Correlations between HU values and DEXA-equivalent BMD (mg/cm2) and T values were computed. Predictive power for osteoporosis was evaluated using ROC curve analysis. Results: Cancellous bone density in the proximal femur showed a significant decline with increasing age and decreasing BMI (p < 0.05). The median BMD for the entire hip was 0.684 mg/cm2, and the median HU value for the proximal femur was 123.15. Strong correlations were observed between HU values and BMD (R2 = 0.904, p < 0.001) and T values (R2 = 0.911, p < 0.001). A T value of −2.5 corresponded to an HU value of 95.79 in the entire femur. ROC analysis demonstrated high sensitivity (0.92) and specificity (0.93) for HU-based osteoporosis prediction. Conclusions: HU measurements provide a reliable method for estimating BMD and T values in the proximal femur, offering a valuable diagnostic tool for osteoporosis. The highest predictive accuracy was achieved when using an irregular ROI from the entire proximal femoral region.

Feasibility study on measuring anteversion angle of acetabular prosthesis after total hip arthroplasty using arbitrary point method

To explore the reliability and accuracy of the arbitrary point method for measuring the anteversion angle of acetabular prosthesis after total hip arthroplasty (THA) based on pelvic X-ray films. The clinical data of 23 patients (25 hips) who underwent THA between December 2018 and September 2023 and met the selection criteria were retrospectively analyzed. Among them, there were 16 males and 7 females, with an average age of 57.6 years (range, 34-81 years); 13 hips had THA on the left side and 12 on the right side. There were 19 cases (21 hips) of osteonecrosis of the femoral head, 2 cases (2 hips) of femoral neck fractures, 1 case (1 hip) of developmental dysplasia of the hip, and 1 case (1 hip) of osteoarthritis. After THA, all patients underwent X-ray examination and CT scan. Three physicians measured the anteversion angle of acetabular prosthesis using the arbitrary point method and the CT measurement method respectively, and repeated the measurements three times. The results of the two measurement methods were compared, and the intraclass correlation coefficient (ICC) was employed to assess the reproducibility of the methods. The anteversion angles of acetabular prosthesis were (15.87±7.73)° measured by the arbitrary point method, and (15.31±7.89)° measured by CT measurement method. There was no significant difference between the two methods ( t=1.515, P=0.143). The ICC of the measurement results by the arbitrary point method for the three physicians were 0.97 ( P<0.001), 0.96 ( P<0.001), and 0.96 ( P<0.001), respectively; and the ICC of the measurement results by CT method were 0.93 ( P<0.001), 0.93 ( P<0.001), and 0.94 ( P<0.001), respectively. The arbitrary point method for measuring the anteversion angle of acetabular prosthesis after THA based on pelvic X-ray film is easy to operate, accurate, and has high reproducibility.

Rainwater uptake in conifer twigs: Five experiments tell a story of absorption, storage, and transport.

While evidence supports the idea that a portion of the many raindrops that fall onto a forest canopy may be directly absorbed by the twigs they lands on, we do not know how much is absorbed, how it enters the twig, or what internal path it might take on its way to the xylem. Using a diverse series of 5 experiments encompassing isotopic labeling, fluorescent tracers, rehydration kinetics, synchrotron-based X-ray tomographic microscopy, and thermal imaging, we follow the fate of rainwater from initial contact with the twig to its distribution to adjacent tissues. We provide conclusive, multi-pronged evidence of surface water-absorption into the xylem of year-old conifer twigs with incomplete bark development. Additionally, we demonstrate a surface capillary phase, mixed apoplastic and symplastic internal routes, and the strong influence of intercellular airspace as a hydraulic capacitor across multiple tissues. We show that twigs are capable of rapid, large-volume water absorption which may help trees take advantage of crown-wetting events and support the repair of hydraulic damage from frost and drought. Forecasting the impacts of climatic stress on different tree species will benefit from understanding the importance, and tissue-level specifics, of this critical water-acquisition pathway. Our works tells a detailed story of rain absorption and lays a foundation for future trait-based research into among-species differences in absorption capacity.

Testing Adam-Gibbs relationship in tapped granular packings

Disordered granular packings share many similarities with supercooled liquids, particularly in the rapid increase of structural relaxation time within a narrow range of temperature or packing fraction. However, it is unclear whether the dynamics of granular materials align with those of their corresponding thermal hard sphere liquids, and the specific influence of friction in a granular system remains largely unexplored. Here, we experimentally study the slow relaxation and the steady state of monodisperse granular sphere packings under vertical tapping using X-ray tomography. We first calculate the thermodynamic parameters including the effective temperature and configurational entropy under the Edwards’ ensemble of packings of granular spheres with varying friction, and measure their characteristic relaxation time during compaction. We then present a unified picture of the relaxation process in granular systems, in which a generalized Adam-Gibbs relationship is followed. These results clarify the close relationship between granular materials and the ideal frictionless hard sphere model.

A Novel Deep Learning model for detection of Pneumonia and Covid-19 variants from Chest X-ray images

Pneumonia is an example of a past pandemic and continues to be a serious health concern. In the USA, more than one million people are admitted in hospital with pneumonia every year, leading to about 500,000 deaths. Chest X-ray imaging is an effective and widely utilised method for diagnosing pneumonia and is essential in both healthcare and epidemiological studies. COVID-19, a viral infection initiated in Wuhan, China towards the end of 2019, quickly spread across the globe. It is caused by the Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) and has influenced millions globally. Analyzing X-ray images is regarded as the fastest and simplest methods for discovery, available at a minimal cost in many places. CT scans, on the other way, are a mere advanced imaging technique that can identify small changes in the composition of internal organs. This method uses 3-D computer technology along with X-rays for a more detailed examination. While both CT scans and X-rays provide images of internal body compositions, traditional X-ray images can sometimes occlude, making it difficult to see fine details. The proposed model outlines a framework for classifying COVID-19 variants and predicting new ones. As per the results, the proposed ResNet_Seg achieved an F1 score of 99.96%, which is higher than the CNN and other models tested. The performance of these models is assessed using datasets from SARS and MERS, resulting in accurate predictions. Future work will focus on validating these models using statistical methods. A relative analysis of deep learning models, including CNN, ResNet, and Darknet, is conducted, with performance enhancements achieved through the novel segmentation algorithm and hyperparameter fine-tuning. The results offer insights into developing more effective and reliable diagnostic methodologies for pneumonia and COVID-19 using deep learning and machine learning techniques.

In-Situ Internal Observation of Silicon Composite Anode in All-Solid-State Battery Using X-ray CT.

Silicon is anticipated to be a next-generation anode active material with a high theoretical capacity density of ∼3600 mAh g-1 around room temperature. However, the volume expansion and contraction derived from lithiation (charging) and delithiation (discharging) are understood to be significant challenges. Particularly in all-solid-state batteries, not only does cracking of the silicon particles themselves occur, but also the disruption of contact between silicon and the solid electrolyte, leading to difficulties in maintaining battery performance, which requires a certain level of mechanical restraint for effective battery operation. Therefore, accurately understanding the internal nanometer-order structure of the silicon/solid electrolyte composite electrode under restrained conditions is crucial for improving the performance of all-solid-state batteries by using silicon anodes. In this study, an all-solid-state battery with a composite anode consisting of silicon and the sulfide solid electrolyte Li6PS5Cl was charged and discharged under constrained conditions, and the internal structure during battery operation was observed using in situ computed tomography measurements. As a result of the observation, different cracking modes were identified during charging and discharging. The modes of cracking and subsequent reattachment were observed during the charging process, whereas anisotropic void formation became evident during the discharge process.

Ultrasound Reconstruction Tomography Using Neural Networks Trained with Simulated Data: A Case of Theoretical Gradient Damage in Concrete

Gradient damage processes in cementitious materials are generally produced by chemical and/or physical processes that travel from outside to inside. Depending on the type of damage, it can cause different effects such as decreased porosity, cracking, or steel corrosion in the case of carbonation, or increased porosity, micro-cracks, expansion, and spalling (also present in thermal damage) in the case of external attack by sulphates or acid attack. Therefore, estimating the boundaries of this damage is an essential task for concrete quality assessment. The first objective of this work was to use neural networks (NNs) for ultrasound tomographic reconstruction of concrete samples in order to estimate the advance front in gradient damage. Unlike the usual X-ray tomography, ultrasound tomography is affected by diffraction, among other factors. NNs can learn to compensate for these effects; however, they require a large amount of training data to achieve accurate results. In the case of cement-based materials, obtaining and measuring a real training database could be complicated, expensive, and time-consuming. For this purpose, a training process using simulated measurements was carried out. The second objective of this work was to demonstrate the feasibility of training neural networks through simulations, which reduces costs. Finally, the trained neural network for tomographic reconstruction was evaluated using real cylindrical concrete specimens. Each specimen consisted of an outer cylinder, representing externally exposed cement, and an inner cylinder, simulating the unaffected core. The Structural Similarity Index (SSIM) was used as a metric to assess the reconstruction accuracy, achieving values of 0.95 for simulated signals and up to 0.82 for real signals.

Impact of Soil Compaction on Pore Characteristics and Hydraulic Properties by Using X-Ray CT and Soil Water Retention Curve in China’s Loess Plateau

The Loess Plateau of China, a region highly vulnerable to erosion and climatic variability, faces significant soil degradation exacerbated by intensive agricultural practices and anthropogenic pressures. This study investigates the impacts of incremental soil compaction (P1–P5) on hydraulic properties, pore structure, and water retention across distinct soil textures (sandy loam, loam, clay loam) to address gaps in understanding texture-specific resilience and soil organic carbon (SOC) interactions. Utilizing X-ray computed tomography (CT), soil water retention curve (SWRC) analysis, and the van Genuchten (vG) model, we quantified compaction-induced changes in porosity, connectivity, and hydraulic conductivity, while comparing unsaturated hydraulic conductivity (Kun) predictions derived from mini disc infiltrometer (MDI) and SWRC parameters. Results revealed that fine-textured, SOC-rich soils had greater compaction, preserving macropore connectivity and saturated hydraulic conductivity (Ks), whereas sandy soils pronounced macropore collapse. Compaction homogenized pore distributions, steepened SWRC, and reduced plant-available water. Integration of CT and SWRC methodologies highlighted CT sensitivity to air-filled macropores versus SWRC’s focus on water-retentive micropores. Strong correlation (R2 = 0.94–0.99) between vG parameters from MDI and SWRC validated parameter robustness, though MDI slightly underestimated Kun in clay loam, while SWRC-based models aligned closely with observed data. Integrating CT and SWRC methodologies offers a framework for precision soil health monitoring. In addition to the critical role of SOC and texture in compaction mitigation, there is a need for organic amendments in sandy soil and reduced tillage.

Weathering profile of completely weathered rock from the Dullstroom Formation, South Africa

This study investigates the weathering profile of completely weathered rock derived from the Dullstroom Formation in South Africa. The research emphasizes the significance of the soil-rock interface, particularly the transition between completely weathered rock and residual soil, in understanding mechanical, chemical, and hydraulic behaviours. Field sampling and laboratory analyses, including particle size distribution, Atterberg limits, X-ray fluorescence (XRF), X-ray diffraction (XRD), and X-ray Computed Tomography (XRCT), were conducted. XRCT proved invaluable in visualizing pore geometry, density contrasts, and the persistence of relict rock structures in three dimensions. The findings highlight how structural prominence decreases with increasing weathering intensity, influencing compressibility and porosity. The compressibility of the material correlates better with chemical weathering indices than traditional geotechnical parameters like void ratio or dry density. These insights contribute to the geotechnical characterization of weathered rock profiles and propose structural prominence as a novel parameter for evaluating mechanical behaviour across weathering stages.

Guided Water Percolation in 3D-Printed Gas Diffusion Layers for Polymer Electrolyte Fuel Cells.

The accumulation of liquid water in the gas diffusion layer (GDL) and associated clogging of the reactant pathways are limiting factors for the performance of polymer electrolyte fuel cells (PEFC). The design and manufacturing of GDLs with a deterministic pore space have the potential to accelerate the development of next-generation PEFC with an optimized balance between reactant supply and product removal. In this study, we explore the potential of GDLs with tailored pore structures obtained from the carbonization of a 3D-printed precursor. Three different GDL designs are investigated by using operando X-ray radiography and subsequent X-ray tomography to track the water pathways. The results confirm the effectiveness of the designed features in terms of controlled liquid water percolation and reveal a trend toward vapor phase transport rather than liquid transport of water away from the catalyst layer interface along with a strong convective flow within the highly porous ordered structures.

Minimal vertical transport of microplastics in soil over two years with little impact of plastics on soil macropore networks

Plastics used in agriculture improve productivity and resource efficiency. As they fragment over time, microplastics are unintentionally released into soil, raising concerns regarding long-term implications for soil structure and fertility. Here we investigated microplastics transport and their impact on soil structure through a two-year field experiment. 45 re-packed soil columns were installed with three treatments: indium-doped polyethylene terephthalate fragments or fibers in the top 2 cm and a control with no microplastics. Soil pore structure was monitored with X-ray tomography, and microplastics vertical transport was assessed via the indium tracer. With time macropore volume, biopore fraction and critical pore diameter increased independent of microplastic addition. Microplastic transport was minimal, with only ~1% reaching below 8 cm soil depth in two years. This experimental design, simulating natural soil conditions, suggests that microplastics have a negligible influence on soil macropore architecture and its transport rate is limited in the short term.

Investigating Bubble Formation and Evolution in Vanadium Redox Flow Batteries via Synchrotron X-Ray Imaging.

The parasitic hydrogen evolution reaction (HER) hinders electrolyte transport. It reduces the effective electrochemical surface area in the negative half-cell of vanadium redox flow batteries (VRFBs), resulting in substantial efficiency losses. We investigated the formation and evolution of hydrogen bubbles within VRFB electrodes through comprehensive experimental characterization and a detailed analysis of the resolved bubbles. The electrode was imaged using synchrotron X-ray tomography, and gas bubbles in the images were identified and characterized using a deep learning model combined with a morphological analysis tool. The HER intensity increases at more negative working electrode potentials, causing residual bubbles to grow and fuse in the electrode central region. In contrast, independent bubbles predominantly form at the electrode edges. Furthermore, the bubble growth leads to the gradual development of irregular shapes. These observations provide insights into bubble formation and evolution rules, contributing to a better understanding of the system.

IMPPY3D: Image Processing in Python for 3D Image Stacks.

Image Processing in Python for 3D image stacks, or IMPPY3D, is a free and open-source software (FOSS) repository that simplifies post-processing and 3D shape characterization for grayscale image stacks, otherwise known as volumetric images, 3D images, or voxel models. While IMPPY3D, pronounced impee-three-dee, was originally created for post-processing image stacks generated from X-ray computed tomography (XCT) measurements, it can be applied generally in post-processing 2D and 3D images. IMPPY3D includes tools for segmenting volumetric images and characterizing the 3D shape of features or regions of interest. These functionalities have proven useful in 3D shape analysis of powder particles, porous polymers, concrete aggregates, internal pores/defects, and more (see the Research Applications section). IMPPY3D consists of a combination of original Python scripts, Cython extensions, and convenience wrappers for popular third-party libraries like SciKit-Image (Walt et al., 2014), OpenCV (Bradski, 2000), and PyVista (Sullivan & Kaszynski, 2019). Highlighted capabilities of IMPPY3D include: varying image processing parameters interactively, applying numerous 2D/3D image filters (e.g., blurring/sharpening, denoising, erosion/dilation), segmenting and labeling continuous 3D objects, precisely rotating and re-slicing an image stack in 3D, generating rotated bounding boxes fitted to voxelized features, converting image stacks into 3D voxel models, exporting 3D models as Visualization Toolkik (VTK) files for ParaView (Ayachit, 2015), and converting voxel models into smooth mesh-based models. Additional information and example scripts can be found in the included ReadMe files within the IMPPY3D GitHub repository (Moser, Landauer, et al., 2024). As a visualized example, Figure 1 demonstrates the high-level steps to characterize powder particles using IMPPY3D. This workflow is also similar to how pores can be visualized and characterized in metal-based additive manufacturing. Additional research applications for IMPPY3D are discussed in a later section.

New NIR-Activated Organic Molecule-Based Nanocomposite as an Efficient Sensitizer for Photothermal and Photodynamic Therapy of Cancer.

Acceptor-donor-acceptor (A-D-A)-configured molecules with coplanar dithieno[2,3-d:2',3'-d']thieno[3,2-b:3',2'-b']dipyrrole (DTPT) as the core are promising organic semiconductor materials utilized in organic photovoltaic devices owing to their efficient charge transportation capabilities. In addition to optoelectronic applications, they are potential in photothermal and photodynamic applications due to their light-absorption properties. This study evaluates the utilization of DTPT-based fused-ring-conjugated small molecules with strong near-infrared (NIR) absorption as stable organic photosensitizers for phototherapy by forming nanoparticles (NPs) with D-α-tocopherol polyethylene glycol 1000 succinate (TPGS). Among them, NPs prepared from the 2-(3-cyano-4,5,5-trimethylfuran-2(5H)-ylidene)malononitrile (TCF) end-capping DTPT-centered molecule, DTPTTCF, exhibit low cytotoxicity, enhance photothermal conversion efficiency and superior photodynamic activity. In vitro and in vivo experiments demonstrate the remarkable anticancer efficacy of DTPTTCF@TPGS NPs that can effectively suppress cancer cell proliferation under 808nm laser treatment. Additionally, soft X-ray tomography (SXT) is employed as a high-resolution tool to observe intracellular variations that reveal distinct vacuolization in the NPs + Laser treated group. These observations highlight that the DTPTTCF@TPGS NPs cause significant damage to cancer cells under NIR irradiation. Furthermore, in vivo, experiments demonstrate the apoptosis of cancer cells within tumor tissues and the effective elimination of tumors upon NIR irradiation of DTPTTCF@TPGS NPs treated mice. This work manifests the potential application of the DTPT-cored A-D-A-type molecule as an advanced agent for tumor phototherapy with enhanced efficacy and selectivity.

Swelling-Induced Shear Failure in Sand-Hydrogel Mixtures: An X-ray CT Study

Abstract Hydrogels have been identified as environmentally friendly and sustainable soil additives for improving soil properties for agricultural and geotechnical engineering purposes. The swelling of hydrogel particles during the wetting process leads to soil restructuring, fundamentally altering the mechanical behaviour of treated soils. This study presents an experimental investigation of the wetting process of sand-hydrogel mixture in triaxial conditions and its impact on shearing behaviour. X-ray tomography is employed to visualize hydrogel swelling and fabric change at particle- and pore-scale. Swelling of hydrogel particles severely affects the soil’s structural rigidity as soil particles are continuously restructured. Eventually, hydrogel swelling induces shear failure under constant deviatoric load and the formation and activation of shear zones.

Investigation of the Breakage Behaviour of Completely Decomposed Granite Under Shear Using X-ray Tomography

Abstract Noise reduction and extraction of microscopic details have been persistent challenges in microstructure visualization. This study monitors the breakage behavior of a reconstituted completely decomposed granite (CDG) sample within a medium-sized triaxial loading device using X-ray microtomography techniques (CT). We use a new filter, non-local means (NL-means), to denoise CT images. NL-means shows a good performance in noise reduction and edge sharpening. Microfractures within the particles are extracted by the black top-hat (BTH) transformation and introduced into particle fragmentation analysis. Changes in CDG particle morphology are analyzed by observing the evolution of aspect ratio, convexity, sphericity and roundness at different strains. We further study the degree of particle breakage with the evolution of relative breakage and relative fractal dimension.

Fiber-Grains Interaction Mechanisms in Triaxial Tests Detected with X-ray Tomography

Abstract Fiber orientation plays a key role in fiber reinforcement. Fibers must undergo tensile stress to be effective and must be oriented along the minimum principal stress direction to ensure maximum interaction with the shear band. When fibers are well oriented, during shearing, porosity and strain fields are more homogeneous in the specimen, and the shear band thickness is larger. The present study is focused on the detection of the interaction mechanism between sand grains and fibers, to link the behavior observed at the macroscale with the microscale. An investigation of the soil-fibers contact would disclose the mechanisms that take place locally and affect the global behavior of the soil assembly, providing great benefits for the reinforcement’s design and performance predictions. Fiber-reinforced sand is subjected to miniature triaxial compression test and X-ray imaging. Continuum and discrete Digital Image Correlation (DIC) analysis is performed to detect fiber-grain interaction mechanisms.

Investigations on Particle Migration During Suspension Injection Through Porous Medium Using X-Ray CT

Abstract Understanding the flow of suspensions through porous media is crucial, particularly in applications such as grouting, waterflooding, and hydraulic fracturing. Previous research indicates that the investigations into the mechanisms underlying the transient coupled flow phenomenon have been insufficient to fully understand the complex phenomenon. The present study employs an experimental methodology, aided with X-ray CT images, to examine the particle migration process resulting in the formation of an internal filer cake and other migration characteristics. This study comprehensively investigates the qualitative and quantitative evolution of particle migration alongside the filter cake formation. In this study, drilling fluid is used as a suspension to investigate particle migration. It is observed that both the filter cake and the filtration zone expand over time, leading to an increase in the injection pressure.

Uncovering the role of steel slag in CO2-cured UHPC: Evaluation on impact resistance, carbonation kinetics and microstructure with X-ray CT

Uncovering the role of steel slag in CO2-cured UHPC: Evaluation on impact resistance, carbonation kinetics and microstructure with X-ray CT