Computed Tomography Techniques Research Articles

Relative estimation of scattering noise and electronic noise of a radiation detector

This study investigates two unavoidable noise factors: electronic noise (EN) and radiation scattering, associated with detectors and their electronics. This study proposes a novel methodology to estimate electronic and scattering noise separately. It utilizes mathematical tools, namely, Kanpur theorem-1 (KT-1), standard deviation, similarity dice coefficient parameters, and experimental computerized tomography technique. Four types of gamma detectors: CsI (Tl), , NaI (Tl) and HPGe are used with their respective electronics. A detector with integrated circuit electronics imparts significantly less (∼33% less) EN in data than detectors with distributed electronics. KT-1 signature is proposed as a scattering error estimate. The developed empirical expression shows that scattering noise depends strongly on the mass attenuation coefficients of detector crystal material and weakly on their active area. The difference between predicted and estimated relative scattering is 14.6%. The methodology presented in this study will assist the related industry in selecting the appropriate detector of optimal diameter, thickness, material composition and hardware as per requirement.

Advanced imaging and quantification of the cambium and developing xylem in eucalypts using X-ray micro- and nano-computed tomography

Summary In recent years, the popularity of X-ray computed tomography (CT), as a non-destructive imaging technique, has continued to expand in various research domains. In wood research, X-ray CT has proven to be useful for three-dimensional (3D) structural studies investigating the complex tissues of trees. Wood formation (i.e., xylogenesis) initiates in the cambium and a narrow zone of subsequent differentiation, both of which play key roles in plant growth and development. However, the dynamics of xylogenesis in eucalypts remain relatively poorly understood, in large part due to challenges in sampling, imaging, and characterizing the cambium. Therefore, the aim of this study was to present a workflow to evaluate the feasibility of using X-ray CT to characterize and quantify the structural properties of the cambium in eucalypts. The growth responses of Corymbia hybrid seedlings, exposed to either irrigated or droughted conditions, was investigated by monitoring the structural development of the cambium. To track microstructural changes in the cambium, the same seedlings were imaged with X-ray micro-CT (μCT) one day before the treatments and again six days after the respective treatments. After the last X-ray μCT scan, X-ray nano-CT was also applied. Using image analysis techniques, the morphological characteristics of the cambium could be determined. X-ray μCT displayed a larger, thicker cambial zone in irrigated plants, while a much thinner cambium was visible in droughted seedlings. X-ray nano-CT revealed that droughted plants were associated with a significantly () smaller cambium volume containing smaller cells, compared to the cambium of irrigated plants. Light microscopy was used to validate the CT results and demonstrated no significant () difference in the cambium width and cell diameter obtained from the two respective CT techniques. The findings of this study proved X-ray CT to be a valuable tool for examining the effect of changing environmental conditions on the complex cambium structure of Corymbia hybrid seedlings.

Investigation of fiber length distribution on crack resistance mechanism of basalt fiber asphalt mixture based on digital image processing technology

Basalt fiber has been widely used to enhance the crack resistance performance of asphalt mixtures. The length of the fiber is an essential parameter to affect the reinforcement effect. However, the research on fiber length distribution (FLD) on the anti-cracking mechanism of asphalt mixtures is still limited.This study aims to present an efficient methodology considering the FLD effect for investigating the crack resistance mechanism of basalt fiber asphalt mixture (BFAM). The X-ray computed tomography (CT) and discrete element (DE) simulation techniques are used to obtain morphological parameters of the BFAM correlated with the FLD (i.e. aggregate skeleton gap size parameters). Then, three indoor cracking tests of the BFAM at low and medium temperatures (i.e. trabecular bending test, IDEAL-CT test and SCB test) are conducted to investigate the relationship between crack resistance performance and morphological parameters. Influences of FLD on the fracture property indexes of the BFAM are discussed.Results indicate that the optimal FLD for the best anti-cracking performance of the BFAM with a specific dense-graded gradation can be found by using digital image processing technology. The morphological parameter of the longest axis of the aggregate skeleton gap is identified as the optimal FLD, which can significantly improve the fracture energy and fracture property indices of the BFAM compared with other FLDs. Under the same fiber content, the fracture energy enhancement of BFAM with different FLDs varies from 7.63% to 106.87%. As for the fracture property indices, the enhancement of the εB in trabecular bending test, CTindex in IDEAL-CT test, and FI in SCB test varies from 17.42% to 39.30%, 13.00% to 162.99%, and 7.46% to 77.61%, respectively. The results demonstrate that fiber length distribution indeed impacts the cracking resistance of the BFAM. The X-ray CT and DE simulation techniques are proved to be both highly efficient approaches for seeking the optimal FLD in the BFAM.

Prognostic role of serum soluble ST2 of advanced breast cancer patients: a retrospective cohort study.

The soluble suppression of tumorigenicity 2 receptor (sST2) binds to interleukin-33 (IL-33) and blocks IL-33 and ST2 binding, suggesting that sST2 acts as a "decoy" receptor for IL-33 and is involved in the malignant progression of breast cancer. This paper aimed to investigate the differences in sST2 expression in patients with different molecular subtypes of breast cancer and assess its clinical value in the prognostic evaluation of advanced breast cancer. In this paper, we collected sera from 91 patients firstly diagnosed with advanced breast cancer at the Tianjin Medical University Cancer Institute and Hospital from 2008 to 2021 during their first hospitalization. We detected the expression level of sST2 in the serum of patients with different molecular fractions of breast cancer and analyzed the relationship between serum sST2 levels and breast cancer-related bone metastasis, cardiotoxicity, and overall survival. Bone metastases were detected using the Emission Computed Tomography technique, and chemotherapy drug-induced cardiotoxicity was detected by echocardiography. The Overall Survival was evaluated using the Kaplan-Meier estimator, and multivariate Cox regression analysis was performed to demonstrate the association between variables and sST2 levels. Serum sST2 levels did not vary among the different pathological types, molecular types, and estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2), and tumor proliferation marker (Ki-67) subgroups, and only differed significantly in the cardiotoxicity group. There were no statistical differences in tissue polypeptide specific antigen (TPSA), carbohydrate antigen 125 (CA125), carcinoembryonic antigen (CEA), carbohydrate antigen 153 (CA153), D-dimer, and inflammatory indexes neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR) among different molecular subgroups. However, except for triple-negative breast cancer (TNBC), there was no difference in peripheral blood soluble ST2 concentrations among other molecular subtypes. Meanwhile, the survival of the high sST2 level group among advanced breast cancer patients was significantly lower than that of the normal group, and sST2 expression was closely related to cardiotoxicity and clinical stage. Serum sST2 is not only traditionally applied to the assessment of cardiac injury, but can also be utilized for assessing the prognosis of advanced breast cancer, excluding the influence of clinical stage and cardiotoxicity.

Experimental characterization of impact damage in foam-core sandwich structures using acoustic emission, optical scanning and X-ray computed tomography techniques

Sandwich structures used in transportation and energy industries are commonly subjected to low-velocity impact in the course of manufacturing, service and maintenance, which can lead to the premature degradation of structural stiffness and strength. A single non-destructive evaluation technique is often difficult to provide a comprehensive assessment on impact damage from online to offline and from visible to invisible. In the present study, acoustic emission (AE), three-dimensional (3D) optical scanning and X-ray computed tomography (CT) techniques are combined to provide a systematic approach for damage characterization of thick foam-core sandwich panels under low-velocity impact. In the tests, the mechanical responses such as force-time and force-displacement curves are obtained from the testing system. The AE technique is adopted to monitor damage initiation and evolution in situ; optical scanning and X-ray computed tomography techniques are used for off-line damage identification and quantification. The results show that the AE signal waveform stream, cumulative counts and cumulative energy correlate well with the mechanical responses of the sandwich panel under the low-velocity impact, enabling capture of valuable information for online damage monitoring. Unlike general cases, the AE signals generated from low-velocity impact are found to be presented in strong bursts of nearly coincident events in the short duration. Therefore, the distributions of AE amplitude and peak frequency between adjacent AE counts are extracted to study the different damage modes and damage mechanisms. The X-ray computed tomography images enable to precisely visualize the fracture behaviors of the PET foam-core inside the sandwich panel in a nondestructive fashion, which evidently supports the AE and optical scanning results. The study is anticipated to demonstrate effectiveness and capability of the proposed experimental methodology for damage detection and characterization on sandwiched composite structures subjected to impact loading.

Morphological and hydrodynamic properties of hydrates during dissociation in sediment

The formation and dissociation of hydrate at the pore scale can be observed qualitatively using μ-CT X-ray imaging. However, a quantitative criterion for hydrate pattern is not currently available in the literature. To fill this research gap, we generated numerically-simulated sediments with specific hydrate formation patterns and accurate hydrate saturation levels, by integrating X-ray computed tomography techniques, morphological operation algorithm, and quartet structure generation set method. Using the topological information extracted from the generated hydrate-bearing sediments, we proposed a quantitative criterion for the microscopic classification of hydrates (namely pore-floating, cementing, and bridging) based on the complexity of pore topology (Tp) and hydrate topology (Th). In this work, we visualized 3D distribution of hydrate utilizing μ-CT imaging technology, as well as analyzed the topology of hydrate and its dynamic evolution through extracted dual-network models and proposed classification method. Our findings demonstrate that when the hydrate saturation exceeds 30%, the dominating hydrate patterns are bridging and pore-floating, while sediment is more likely to exhibit cementing and pore-floating patterns when the hydrate saturation is below this threshold. Additionally, we applied the lattice Boltzmann method to numerically analyze the variation of normalized permeability and tortuosity under different hydrate saturation levels. The permeability monotonically increases as hydrate dissociates from the sediments, while the behaviour of tortuosity is non-monotonic.

Aspects of Choosing the Technique of Computed Tomography in the Diagnostics of Maxillofacial Dysostosis

Maxillofacial dysostoses are congenital malformations of organs of head and neck, developing from the I and II gill arches. It is important to carry out differential diagnostics based on a comprehensive basic and additional examination aimed at determining all intracranial and extracranial symptoms specific for concrete syndrome, which is possible with modern methods of radiological diagnostic — CBCT and MSCT. The purpose of the study is to determine key aspects of choosing the computed tomography technique for diagnostics of maxillofacial dysostoses. From 2009 to 2023 215 MSCT and 86 CBCT were performed in 211 patients aged from 2 to 18 years old with maxillofacial dysostoses for the purpose of differential diagnostics of pathology, indications for choosing the volume of radiological examination were determined.

Multi-modality imaging in aortic stenosis: an EACVI clinical consensus document.

In this EACVI clinical scientific update, we will explore the current use of multi-modality imaging in the diagnosis, risk stratification, and follow-up of patients with aortic stenosis, with a particular focus on recent developments and future directions. Echocardiography is and will likely remain the key method of diagnosis and surveillance of aortic stenosis providing detailed assessments of valve haemodynamics and the cardiac remodelling response. Computed tomography (CT) is already widely used in the planning of transcutaneous aortic valve implantation. We anticipate its increased use as an anatomical adjudicator to clarify disease severity in patients with discordant echocardiographic measurements. CT calcium scoring is currently used for this purpose; however, contrast CT techniques are emerging that allow identification of both calcific and fibrotic valve thickening. Additionally, improved assessments of myocardial decompensation with echocardiography, cardiac magnetic resonance, and CT will become more commonplace in our routine assessment of aortic stenosis. Underpinning all of this will be widespread application of artificial intelligence. In combination, we believe this new era of multi-modality imaging in aortic stenosis will improve the diagnosis, follow-up, and timing of intervention in aortic stenosis as well as potentially accelerate the development of the novel pharmacological treatments required for this disease.

Characterization of self-piercing rivet joints using X-ray computed tomography

Self-piercing rivet (SPR) joining is a process that has been adopted in the automotive industry, and it is important to be able to characterize SPR joints non-destructively. X-ray computed tomography (CT) allows visualizing the internal structure of the sample whilst preserving the workpiece. In this work, the application of X-ray CT to SPR joint characterization is investigated. Many features of a riveted joint can be observed. This includes the boundary between sheet interfaces and the positions where the substrates and rivet meet, which are important to quality assessment. In the case of similar materials, some of these features become difficult to observe but the presence of adhesive between the sheets enables the features to be more easily observed. Furthermore, substrate fracture and rivet cracks, radial cracks and the asymmetry of SPR joints can be detected due to the difference in greyscale to the surrounding materials. It is also revealed that image resolution plays an important role in defect detectability of the X-ray CT technique.

Experimental and Numerical Analysis of Stitched Composite Laminates Subjected to Low-Velocity Edge-on Impact and Compression after Edge-on Impact.

Composite laminates are susceptible to impact events during use and maintenance, affecting their safety performance. Edge-on impact is a more significant threat to laminates than central impact. In this work, the edge-on impact damage mechanism and residual strength in compression were investigated using experimental and simulation methods by considering variations in impact energy, stitching, and stitching density. The damage to the composite laminate after edge-on impact was detected in the test by visual inspection, electron microscopic observation, and X-ray computed tomography techniques. The fiber and matrix damage were determined according to the Hashin stress criterion, while the cohesive element was used to simulate the interlaminar damage. An improved Camanho nonlinear stiffness discount was proposed to describe the stiffness degradation of the material. The numerical prediction results matched well with the experimental values. The findings show that the stitching technique could improve the damage tolerance and residual strength of the laminate. It can also effectively inhibit crack expansion, and the effect increases with increasing suture density.

Micro-defect characterization and growth mechanism of plasma electrolytic oxidation coating on 6082-T6 alloy

This work reports micro-defects and growth mechanism of the plasma electrolytic oxidation (PEO) coating formed on the surface of 6082-T6 aluminum alloy. Scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray computed tomography techniques were used to characterize the morphology, phase, microstructure, and porosity of the PEO coating, respectively. The results confirmed a porous outer layer and a dense inner layer in the coating. The PEO coating was composed of γ- and α-Al2O3 phases, and amorphous phases. A layer with only amorphous structures was found near the coating/substrate (C/S) interface, which could be ascribed to the high concentration of P element in the electrolyte. Micro-defects with different sizes and shapes inside the coating were successfully characterized by the high-resolution X-ray computed tomography technique, and the volume reconstruction result revealed a porosity fraction of 5.43% for the coating. A growth model was complemented to explain the growth mechanism and interconnected micro-defects of the PEO coating.

Detection of tracheal branching with computerized tomography: The relationship between the angles and age-gender.

The data obtained on the anatomical knowledge of the tracheobronchial system can be used for diagnosis, treatment and interventional interventions in areas such as anesthesia, thoracic surgery, pulmonary physiology. To determine the tracheobronchial branching angles in pediatric and adult populations by using the multislice computed tomography (CT) and minimum intensity projection (MinIP) technique, which is a non-invasive method. Our study was carried out retrospectively. Patients who underwent contrast and non-contrast CT examination, whose anatomically and pathophysiologically good tracheobronchial system and lung parenchyma images were obtained, were included in the study. Measurements were made in the coronal plane of the lung parenchyma. In the coronal plane, right main bronchus-left main bronchus angle, right upper lobe bronchus-intermedius bronchus angle, right middle lobe bronchus-right lower lobe bronchus angle, left upper lobe bronchus-left lower lobe bronchus angle were measured. The study population consisted of 1511 patients, 753 pediatric (mean age: 13.4 ± 4.3; range: 1-18 years) and 758 adults (mean age: 54.3 ± 17.3; range: 19-94 years). In our study, tracheal bifurcation angle was found to be 73.3° ± 13.7° (59.6°-87°) in the whole population. In the pediatric group, the right-left main coronal level was found to be higher in boys compared to girls (74.6° ± 12.9° vs 71.2° ± 13.9°, P = 0.001). In the adult group, the right-left main coronal level was found to be lower in males compared to females (71.9° ± 12.9° vs 75.8° ± 14.7°, P < 0.001). Our study, with the number of 1511 patients, is the first study in the literature with the largest number of patient populations including pediatric and adult demographic data, measuring the angle values of the tracheobronchial system using multislice CT and MinIP technique. Study data will not only be a guide during invasive procedures, but it can also guide studies to be done with imaging methods.

Multi-level X-ray computed tomography (XCT) investigations of commercial lithium-ion batteries from cell to particle level

Adopting X-ray computed tomography (XCT) for ex-situ characterization of battery materials has gained interest in the past decade. The main goal of this paper is to demonstrate the effectiveness of several X-ray computer tomography techniques to study commercial batteries. General guidelines are provided to select the most suitable imaging equipment and parameters for investigations of lithium-ion batteries, spanning the length scales from cell to electrode, down to particle level. Relevantly, such parameters would also be suitable for operando experiments. Safety mechanisms and manufacturing inconsistencies at cell level as well as defects and inhomogeneity in cathode and anode is illustrated and quantified. Furthermore, relation of beam energy and sample-detector-distance on contrast retrieved from attenuation and phase shift is inspected using Synchrotron XCT.

From micro- to nano- and time-resolved x-ray computed tomography: Bio-based applications, synchrotron capabilities, and data-driven processing

X-ray computed microtomography (μCT) is an innovative and nondestructive versatile technique that has been used extensively to investigate bio-based systems in multiple application areas. Emerging progress in this field has brought countless studies using μCT characterization, revealing three-dimensional (3D) material structures and quantifying features such as defects, pores, secondary phases, filler dispersions, and internal interfaces. Recently, x-ray computed tomography (CT) beamlines coupled to synchrotron light sources have also enabled computed nanotomography (nCT) and four-dimensional (4D) characterization, allowing in situ, in vivo, and in operando characterization from the micro- to nanostructure. This increase in temporal and spatial resolutions produces a deluge of data to be processed, including real-time processing, to provide feedback during experiments. To overcome this issue, deep learning techniques have risen as a powerful tool that permits the automation of large amounts of data processing, availing the maximum beamline capabilities. In this context, this review outlines applications, synchrotron capabilities, and data-driven processing, focusing on the urgency of combining computational tools with experimental data. We bring a recent overview on this topic to researchers and professionals working not only in this and related areas but also to readers starting their contact with x-ray CT techniques and deep learning.

Spectral CT imaging: Technical principles of dual-energy CT and multi-energy photon-counting CT.

Spectral computed tomography (CT) imaging encompasses a unique generation of CT systems based on a simple principle that makes use of the energy-dependent information present in CT images. Over the past two decades this principle has been expanded with the introduction of dual-energy CT systems. The first generation of spectral CT systems, represented either by dual-source or dual-layer technology, opened up a new imaging approach in the radiology community with their ability to overcome the limitations of tissue characterization encountered with conventional CT. Its expansion worldwide can also be considered as an important leverage for the recent groundbreaking technology based on a new chain of detection available on photon counting CT systems, which holds great promise for extending CT towards multi-energy CT imaging. The purpose of this article was to detail the basic principles and techniques of spectral CT with a particular emphasis on the newest technical developments of dual-energy and multi-energy CT systems.

Distribution development of pore/crack expansion and particle structure of cemented solid-waste composites based on CT and 3D reconstruction techniques

This work analyzes the effects of Industrial solid waste content and meso-microstructure on the mechanical and fracture behavior of cemented solid-waste composites (CSWC). The mechanical properties of CSWC were investigated using uniaxial compression tests. Quantitative analysis of pore and particle structure and cracks was performed using X-ray computed tomography (CT). In addition, the effects of solid waste content and porosity on the Uniaxial compressive strength (UCS) of CSWC were analyzed, and the effects of pore and steel slag (SS) particle distribution on crack expansion were investigated. The results show that the optimization of solid waste content can improve the pore structure of CSWC and promote the uniform distribution of SS particles within CSWC. SS content is 40 wt%, SS is the main factor affecting the strength of CSWC, SS content is less than 40 wt%, porosity and fly ash (FA) are the main factors affecting the strength of CSWC. Connected pores and microcracks are prone to develop as cracks under the action of external loads. Porosity is less than or equal to 0.10%, pore size is not related to crack development. SS content is greater than 10 wt%, particle structure affects crack development.

A Pore-Scale Physical Model for Electric Dewatering of Municipal Sludge Based on Fractal Geometry

Water in municipal sludge has an electric double layer (EDL), and can be rapidly removed via electroosmosis. However, the understanding of the physical mechanisms of electroosmosis is limited owing to the complex pore structure of sludge porous media, which may restrict the development of electric dewatering (EDW) technology. In this study, the sludge microstructure was measured using the computerized tomography technique and quantitatively characterized using fractal geometry. A new pore-scale physical model for the electroosmotic flow through sludge porous media was developed based on the EDL theory, and the analytical expressions for the electroosmotic flow rate and permeability coefficient were determined. The proposed fractal pore-scale model for electroosmotic flow was validated by comparing it with the measured electroosmotic flow rate using a self-designed EDW device for municipal sludge composed of a hydraulic system and applied electric field. The results show that the electroosmotic flow rate of sludge porous media depends not only on the applied electric field, but also on the sludge microstructure including porosity, maximum pore size, and pore and tortuosity fractal dimensions. However, the correlation between the electroosmotic flow rate and the voltage gradient was usually nonlinear, and became linear only if the tortuosity fractal dimension equaled to one (straight flow path). The electroosmotic permeability coefficient increases with an increase in porosity; however, it is lowered by the increased pore and tortuosity fractal dimensions under a certain porosity. The electroosmosis phenomenon can effectively remove part of the interstitial water and surface water in sludge porous media, and the proposed electroosmotic physical model provides a useful theoretical basis for the development of EDW technology for municipal sludge.

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.

The application study of dual-energy CT nonlinear blending technique in pulmonary angiography*

Abstract Objective This study aimed to explore the feasibility of enhancing image quality in computed tomography (CT) pulmonary angiography (CTPA) and reducing radiation dose using the nonlinear blending (NLB) technique of dual-energy CT. Methods A total of 61 patients scheduled for CTPA were enrolled, and 30 patients underwent dual-energy scanning. Nonlinear blending images (NLB group) and three groups of linear blending images (LB group, 80 kV group, and 140 kV group) were reconstructed after scanning; 31 patients underwent single-energy scanning (120 kV group). The CT values and standard deviations of the pulmonary trunk, left and right pulmonary arteries, and ipsilateral back muscle at the bifurcation level of the left and right pulmonary arteries were measured. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of the five groups were calculated. The subjective image quality of the five groups was assessed. The radiation doses of the dual- and single-energy groups were recorded and calculated. Results The CNR and SNR values of blood vessels in the NLB group were significantly higher than those in the LB, 140 kV, and 80 kV groups (CNR of pulmonary artery trunk: t = 3.50, 4.06, 7.17, all P &lt; 0.05; SNR of pulmonary trunk: t = 3.76, 4.71, 6.92, all P &lt; 0.05). There were no statistical differences in the CNR and SNR values between the NLB group and 120 kV group (P &gt; 0.05). The effective radiation dose of the dualenergy group was lower than that of the single-energy group (t = -4.52, P &lt; 0.05). The subjective scores of images in the NLB group were the highest (4.28 ± 0.74). Conclusion The NLB technique of dual-energy CT can improve the image quality of CTPA and reduce the radiation dose, providing more reliable imaging data for the clinical diagnosis of pulmonary embolism.

3D anisotropy in shear failure of a typical shale

It is inadequate to study the shear failure anisotropy of shale in only 2D space. Aiming at a 3D analysis, a series of direct shear tests was conducted on Longmaxi shale with three typical bedding orientations: arrester, divider and short-transverse orientations. During testing, acoustic emission (AE) and digital image correlation (DIC) techniques were simultaneously employed to monitor failure development, after testing, X-ray computed tomography (CT) scanning was adopted to acquire and reconstruct the fractures inside typical ruptured samples for more detailed analysis. The results indicated that the shear strength parameters exhibited 3D anisotropies and those of the arrester sample did not have equivalent shear strength parameters to the shale matrix. The maximum (minimum) shear strength and cohesion were obtained with the divider (short-transverse) orientation, and the internal friction angle reached its maximum (minimum) with the divider (arrester) orientation. Combining the AE, DIC and CT techniques, four characteristic stress levels that can capture the progressive shear failure process of shale rocks were identified, and the onset and accelerated development of shear damage-induced dilation were observed at the crack initiation and coalesce stress thresholds, respectively. During the crack coalescence stage, the dominated microcracking mechanism transferred from tensile-mode to shear-mode. For the arrester and divider orientations, more tensile-mode AE events were generated due to the microcracking along the vertical beddings. Compared with the divider samples, a more complex fracture network with a larger fracture area and volume was obtained in the arrester samples, whose strengths were smaller.