Computed Tomography Techniques Research Articles

In vitro static and dynamic cell culture study of novel bone scaffolds based on 3D-printed PLA and cell-laden alginate hydrogel

The aim of this paper was to design and fabricate a novel composite scaffold based on the combination of 3D-printed polylactic acid-based triply periodic minimal surfaces (TPMSs) and cell-laden alginate hydrogel. This novel scaffold improves the low mechanical properties of alginate hydrogel and can also provide a scaffold with a suitable pore size, which can be used in bone regeneration applications. In this regard, an implicit function was used to generate some gyroid TPMS scaffolds. Then the fused deposition modeling process was employed to print the scaffolds. Moreover, the micro computed tomography technique was employed to assess the microstructure of 3D-printed TPMS scaffolds and obtain the real geometries of printed scaffolds. The mechanical properties of composite scaffolds were investigated under compression tests experimentally. It was shown that different mechanical behaviors could be obtained for different implicit function parameters. In this research, to assess the mechanical behavior of printed scaffolds in terms of the strain–stress curves on, two approaches were presented: equivalent volume and finite element-based volume. Results of strain–stress curves showed that the finite-element based approach predicts a higher level of stress. Moreover, the biological response of composite scaffolds in terms of cell viability, cell proliferation, and cell attachment was investigated. In this vein, a dynamic cell culture system was designed and fabricated, which improves mass transport through the composite scaffolds and applies mechanical loading to the cells, which helps cell proliferation. Moreover, the results of the novel composite scaffolds were compared to those without alginate, and it was shown that the composite scaffold could create more viability and cell proliferation in both dynamic and static cultures. Also, it was shown that scaffolds in dynamic cell culture have a better biological response than in static culture. In addition, scanning electron microscopy was employed to study the cell adhesion on the composite scaffolds, which showed excellent attachment between the scaffolds and cells.

Morphological analysis of porosity and sound absorption in sustainable materials from rice husk

This study proposes a composite material that incorporates rice husk. This research focuses on an experimental analysis of the physical, mechanical and acoustic performance of composite materials made of rice-husk waste. Various ratios of rice husk/resins have been employed. Complementary, X-ray computed tomography technique has been used to characterise a representative and extensive volume of material at the pore level, ranging from pore sizes of 100 μm to several millimetres Furthermore, detailed information of key factors of pore properties inside the matrix (pore size, sphericity, position, tortuosity and permeability) has been provided. All the compositions present high sound-absorption coefficients, with noise-reduction coefficients ranging from 0.39 to 0.52, and suitable compressive strength (>1 MPa). From the results, when the rice husk/resin ratio was decreased, the pore size fell between 1 and 4 mm, and the permeability reduced; in contrast, the compressive strength increased, although the sound absorption capacity diminished.

Pulmonary CT scans of white rabbits using the selective photon shield technique of the third-generation dual-source CT

This study aims to optimise the protocol for the low-dose pulmonary computed tomography (CT) scanning of infants by studying the effects of the selective photon shield (SPS) technique of the third-generation dual-source CT (DSCT) on the image quality and radiation dose of a chest CT in white rabbits under different tube currents. Twelve white rabbits of a similar weight to an infant were selected and randomly divided into an experimental group and a control group. The experimental groups (A1–A5) were scanned at low dose by the third-generation DSCT using SPS under different tube current × time (60, 50, 40, 30, and 20 mAs). The control group (B) was scanned under a conventional tube voltage (100 kV) and current × time (20 mAs). Advanced model iterative reconstruction at strength three was used for the objective and subjective evaluation of the image quality and radiation dose of the lung and mediastinal windows. With the standard deviation of the air in the trachea as image noise, the signal-to-noise ratio (SNR), contrast-to-noise ratio, and CT values of each site were evaluated. Radiation doses were compared using the volume CT dose index, dose length product, and effective dose. The differences in subjective image quality between groups A2 and B were not statistically significant (P = 0.34). The differences in the SNRs of the lung and mediastinal windows between groups A2 and B were not statistically significant (P > 0.05). The radiation dose of group A2 was 83.2% lower than that of group B. The SPS of the third-generation DSCT under 50 mAs might be applied in the pulmonary CT examination of infants.

Shear Strength and Mesoscopic Characteristics of Basalt Fiber–Reinforced Loess after Dry–Wet Cycles

Frequent dry–wet cycles induced uneven settlement and slope failure of transportation infrastructures in the Loess Plateau of China. Fiber reinforcement provides a method for solving these problems. In this study, a digital image–based triaxial shear test system was adopted through which to study the dry–wet action on mechanical behavior and failure mode of basalt fiber–reinforced loess. The apparent cracks and mesostructure of fiber-reinforced loess after dry–wet cycles were observed by digital camera and X-ray computed tomography technique (CT). Results show that the shear strength of fiber-reinforced loess decreases after dry–wet cycles, whereas it shows inverted U-shaped variations with fiber content, with the optimal resistance to dry–wet action at 0.6%. Compared with unreinforced loess, the samples with fiber reinforcement show fewer cracks, implying the effectiveness of fibers in inhibiting initiation and propagation of apparent cracks. The failure mode changes from brittle shear failure to overall bulging after fiber addition. The CT scan results showed that the fibers inhibited the generation and propagation of microcracks, and the damage mainly occurred in the early stage of the dry–wet cycles.

Experimental study on ultrasonic irradiation for enhancing coalbed methane recovery

The present study proposes the use of a new ultrasonic irradiation method to enhance permeability and desorption for gas recovery from low-permeability coal reservoirs. A triaxial stress ultrasonic irradiation test apparatus was developed specifically for coal, considering the properties of gas adsorption, migration, and sound intensity, and providing a simultaneous measurement of gas flux, to investigated the deformation and temperature of coal samples obtained from the Fuxin coal field by permeability and desorption experiments. With the ultrasonic irradiation duration, the permeability of coal improved gradually with unequal variation, accompanied by the Klinkenberg effect where it decreased rapidly and then increased slowly with increasing gas pressure. The ability to desorb coal was enhanced by higher sound intensity ultrasound irradiation, and the volume of gas desorption was much greater than that of the sample without mange, the temperature and strain were demonstrated as a “J shaped” curve. An X-ray computer tomography (CT) technique was used to visualise the meso- or macro-cracks in the coal sample at pre- and post- ultrasonic irradiation, consequently, fractures expanded under the irradiation of ultrasonic waves. A permeability and desorption model was developed to describe the improvement of coal seam gas production capacity under ultrasonic irradiation, which introduced effective sound pressure.

Stride: A flexible software platform for high-performance ultrasound computed tomography

Background and objective: Advanced ultrasound computed tomography techniques like full-waveform inversion are mathematically complex and orders of magnitude more computationally expensive than conventional ultrasound imaging methods. This computational and algorithmic complexity, and a lack of open-source libraries in this field, represent a barrier preventing the generalised adoption of these techniques, slowing the pace of research, and hindering reproducibility. Consequently, we have developed Stride, an open-source Python library for the solution of large-scale ultrasound tomography problems.Methods: On one hand, Stride provides high-level interfaces and tools for expressing the types of optimisation problems encountered in medical ultrasound tomography. On the other, these high-level abstractions seamlessly integrate with high-performance wave-equation solvers and with scalable parallelisation routines. The wave-equation solvers are generated automatically using Devito, a domain-specific language, and the parallelisation routines are provided through the custom actor-based library Mosaic.Results: We demonstrate the modelling accuracy achieved by our wave-equation solvers through a comparison (1) with analytical solutions for a homogeneous medium, and (2) with state-of-the-art modelling software applied to a high-contrast, complex skull section. Additionally, we show through a series of examples how Stride can handle realistic numerical and experimental tomographic problems, in 2D and 3D, and how it can scale robustly from a local multi-processing environment to a multi-node high-performance cluster.Conclusions: Stride enables researchers to rapidly and intuitively develop new imaging algorithms and to explore novel physics without sacrificing performance and scalability. This will lead to faster scientific progress in this field and will significantly ease clinical translation.

Origin of micro-scale local hotspots during the microwave processing of the YBCO conductive ceramics

In this letter, in situ investigation on the microstructure evolution of YBa2Cu3O7-x (YBCO) ceramics with a high electrical conductivity on a microscopic scale during microwave heating was carried out by the synchrotron radiation computed tomography technique. The experimental results indicate that the local melting exist inside the particle composed of smaller particles, leading to the heterogeneous heating or thermal runaway, which has not been reported elsewhere. Subsequently, considering the conductivity and morphology of YBCO particles, the novel phenomena has been interpreted by the calculated results from a constructed model, and it reveals that the non-uniform distribution of the focused electric field stems from the high conductivity and aggregated-particles of YBCO. Moreover, the high conductivity in combination with more and smaller aggregated-particles will intensify the non-uniformity of the focused electric field and heterogeneous heating for different microstructures.

Novel Cardiac Computed Tomography Methods for the Assessment of Anthracycline Induced Cardiotoxicity.

Anthracyclines are among the most frequently utilized anti-cancer therapies; however, their use is frequently associated with off-target cardiotoxic effects. Cardiac computed tomography (CCT) is a validated and rapidly evolving technology for the evaluation of cardiac structures, coronary anatomy and plaque, cardiac function and preprocedural planning. However, with emerging new techniques, CCT is rapidly evolving to offer information beyond the evaluation of cardiac structure and epicardial coronary arteries to provide details on myocardial deformation, extracellular volume, and coronary vasoreactivity. The potential for molecular imaging in CCT is also growing. In the current manuscript we review these emerging computed tomography techniques and their potential role in the evaluation of anthracycline-induced cardiotoxicity.

Comparison of Simulated Low-Dose and Conventional-Dose CT for Preoperative Planning in Shoulder Arthroplasty.

Shoulder computed tomography (CT) is commonly utilized in preoperative planning for total shoulder arthroplasty. Conventional-dose shoulder CT may expose patients to more ionizing radiation than is necessary to provide high-quality images for this procedure. The purpose of this study was to evaluate the utility of simulated low-dose CT images for preoperative planning using manual measurements and common preoperative planning software. Eighteen shoulder CT scans obtained for preoperative arthroplasty planning were used to generate CT images as if they had been acquired at reduced radiation dose (RD) levels of 75%, 50%, and 25% using a simulation technique that mimics decreased x-ray tube current. This technique was validated by quantitative comparison of simulated low-dose scans of a cadaver with actual low-dose scans. Glenoid version, glenoid inclination, and humeral head subluxation were measured using 2 commercially available software platforms and were also measured manually by 3 physicians. These measurements were then analyzed for agreement across RD levels for each patient. Tolerances of 5° of glenoid version, 5° of glenoid inclination, and 10% humeral head subluxation were used as equivalent for preoperative planning purposes. At all RD levels evaluated, the preoperative planning software successfully segmented the CT images. Semiautomated software measurement of 25% RD images was within tolerances in 99.1% of measurements; for 50% RD images, within tolerances in 96.3% of measurements; and for 75% RD images, within tolerances in 100% of measurements. Manual measurements of 25% RD images were within these tolerances in 95.1% of measurements; for 50% RD images, in 98.8% of measurements; and for 75% RD images, in 99.4% of measurements. Simulated low-dose CT images were sufficient for reliable measurement of glenoid version, glenoid inclination, and humeral head subluxation by preoperative planning software as well as by physician-observers. These findings suggest the potential for substantial reduction in RD in preoperative shoulder CT scans without compromising surgical planning. The adoption of low-dose techniques in preoperative shoulder CT may lower radiation exposure for patients undergoing shoulder arthroplasty, without compromising image quality.

Synthesis and Laser-Related Spectroscopy of Er:Y2O3 Optical Ceramics as a Gain Medium for In-Band-Pumped 1.6 µm Lasers

In this paper, Er:Y2O3 optical ceramics were fabricated and details of the synthesis were presented. The spectral–luminescent properties of Er3+:Y2O3 optical ceramics were investigated. The absorption and emission cross-section spectra were determined. The luminescence kinetics at near 1.6 µm was single exponential and the lifetime of erbium 4I13/2 energy level was determined. In the frame of the conventional Judd–Ofelt theory, the emission properties of the energy levels of erbium 4I13/2 and 4I11/2 involved in laser operation at near 1.6 µm were calculated. The gain coefficient curves for typical values of the relative population of the upper laser level 4I13/2 were presented. The composition and structure were studied using the SEM, XRD, FTIR spectroscopy, and X-ray computer tomography techniques.

CT-based detection of material flow in friction stir welding of dissimilar Al/Mg alloys with and without ultrasonic assistance

Comparative experiments of friction stir welding (FSW) of Al/Mg alloys were conducted with and without ultrasonic assistance. The copper powders were preset inside the workpieces as the marker material, and computer tomography technique was employed to obtain the three-dimensional information of material flow around the tool. The top view of copper powders distribution inside the weldments shows that the distribution zones of marker material at the retreating side and the trailing side were all widened by the exerted ultrasonic vibration (UV). The front view and side view of marker material distribution demonstrated that UV also enhanced the vertical material flow. Such detection results are helpful to elucidate the mechanism of ultrasonic-assisted FSW of dissimilar Al/Mg alloys.

Super-resolution reconstruction of digital rock CT images based on residual attention mechanism

Computer tomography technology is widely used in geological exploration because it is a nondestructive and three-dimensional imaging method that can be integrated with computer simulation. However, the large-scale application of the computer tomography technique is limited by economic costs and time consumption. Therefore, it is challenging and intractable to indicate the pore structure characteristics of rock. To address this issue, a super-resolution reconstruction algorithm based on convolutional neural networks, residual learning, and attention mechanism was proposed to generate super-resolution images in this study. This algorithm was applied to the reconstruction of carbonate rock and sandstone. The performance of two-dimensional image reconstruction was evaluated by quantitative extraction and qualitative visualization. The results from experiments indicate that the built model performs well on different upscaling factors and is superior to the existing super-resolution approaches based on convolutional neural network. Cited as: Shan, L., Bai, X., Liu, C., Feng, Y., Liu, Y., Qi, Y. Super-resolution reconstruction of digital rock CT images based on residual attention mechanism. Advances in Geo-Energy Research, 2022, 6(2): 157-168. https://doi.org/10.46690/ager.2022.02.07

Diagnostic value and limitations of CT in detecting rib fractures and analysis of missed rib fractures: a study based on early CT and follow-up CT as the reference standard

To evaluate the value and limitations of computed tomography (CT) diagnosis of rib fractures, and to discuss the characteristics of missed rib fractures. One hundred and sixty chest trauma patients who underwent both early CT (within 48 h) and follow-up CT (14 days later) were enrolled. For early CT examinations, the diagnosis of rib fractures was divided into routine assessment and verification assessment. The detection rates of rib fractures in both patterns were calculated, and the characteristics of missed rib fractures were analysed, based on the imaging results of the twice CT examinations as the reference standard. A total of 584 fracture sites were confirmed. The overall detection rate of rib fractures in the routine assessment method was 72.4%. In the verification assessment, the detection rates of rib fractures of four observation strategies (axial images, multiplanar reconstruction [MPR], axial images+volume reconstruction [VR] and MPR+VR) were 76.2%, 79.1%, 78.6%, 80.8%, respectively. The incidence of occult fractures was 19.2% (112/584). In both assessment methods, the detection rates of rib fractures at the costochondral junction were the lowest (60%, 65%, respectively); the detection rates ranged from 63.6% to 74.7% for non-displaced rib fractures, but 100% for displaced rib fractures. Most (78.9%) missed rib fractures were accompanied by visible fractures on the same or adjacent first to second rib. Most missed rib fractures are occult on early CT, which is attributable to the limitations of the CT technique. The number of displaced rib fractures on early CT is a more stable and reliable clinical indicator.

Advanced CT and MR Imaging of the Posttreatment Head and Neck.

Advances in MR and computed tomography (CT) techniques have resulted in greater fidelity in the assessment of treatment response and residual tumor on one hand and the assessment of recurrent head and neck malignancies on the other hand. The advances in MR techniques primarily are related to diffusion and perfusion imaging which rely on the intrinsic architecture of the tissues and organ systems. The techniques exploit the density of the cellular architecture; and the vascularity of benign and malignant lesions which in turn affect the changes in the passage of contrast through the vascular bed. Dual-energy CT and CT perfusion are the major advances in CT techniques that have found significant applications in the assessment of treatment response and tumor recurrence.

Root canal obturation, X-ray, scanner X-ray, radiovisiography, Cone Beam computed tomography.

Root canal obturation needs to preserve optimal clinical conditions for achieving success in patients. The aim of the present study was to evaluate endodontic obturation performed by the lateral condensation technique with manual and rotary instruments. Thirty extracted incisors were divided into two groups according to instrumentation technique: group 1-RCSMA57 + Sealapex® and group 2-spreader iRace #30 + Sealapex®. All samples were decoronated and standardized at 10 mm, intraradicular instrumentation were performed with Gates-Glidden #3, and the protocols of irrigation that were employed were 5.25% NaOCl + 17% EDTA during instrumentation. Finally, the groups were obturated with the lateral condensation technique. The samples were observed with conventional X-ray, scanner X-ray, radiovisiography, and Cone Beam computed tomography techniques. For evaluation, a scale of canal obturation density (0 = suitable, 1 = acceptable, 2 = fair, and 3 = inadequate) was employed by blinded evaluator. A value of canal obturation density was assigned in each sample. A statistical analysis by the χ2 of Pearson with a significance level of 0.05% was employed. All groups showed different values according to the instrumentation technique employed. The rotary instrument gave better results than manual instruments according to the values expressed (p = 0.004). The both instruments can be used in the obturation lateral technique; however, the rotary instrument provides better conditions for this technique.

Diagnosis and monitoring of systemic sclerosis-associated interstitial lung disease using high-resolution computed tomography.

Patients with systemic sclerosis are at high risk of developing systemic sclerosis–associated interstitial lung disease. Symptoms and outcomes of systemic sclerosis–associated interstitial lung disease range from subclinical lung involvement to respiratory failure and death. Early and accurate diagnosis of systemic sclerosis–associated interstitial lung disease is therefore important to enable appropriate intervention. The most sensitive and specific way to diagnose systemic sclerosis–associated interstitial lung disease is by high-resolution computed tomography, and experts recommend that high-resolution computed tomography should be performed in all patients with systemic sclerosis at the time of initial diagnosis. In addition to being an important screening and diagnostic tool, high-resolution computed tomography can be used to evaluate disease extent in systemic sclerosis–associated interstitial lung disease and may be helpful in assessing prognosis in some patients. Currently, there is no consensus with regards to frequency and scanning intervals in patients at risk of interstitial lung disease development and/or progression. However, expert guidance does suggest that frequency of screening using high-resolution computed tomography should be guided by risk of developing interstitial lung disease. Most experienced clinicians would not repeat high-resolution computed tomography more than once a year or every other year for the first few years unless symptoms arose. Several computed tomography techniques have been developed in recent years that are suitable for regular monitoring, including low-radiation protocols, which, together with other technologies, such as lung ultrasound and magnetic resonance imaging, may further assist in the evaluation and monitoring of patients with systemic sclerosis–associated interstitial lung disease. A video abstract to accompany this article is available at: https://www.globalmedcomms.com/respiratory/Khanna/HRCTinSScILD

Investigation of the opto-thermo-mechanical properties of antimicrobial PET/TiO2 fiber using the transport of intensity equation technique.

The transport of intensity equation (TIE) technique is used to investigate the effect of stretching and annealing conditions on the optical features and antimicrobial activity of polyethylene terephthalate (PET) fibers treated with TiO2 nanoparticles. The main core of this paper gets the most preferable optical and mechanical properties for PET/TiO2 fiber which maintains its antibacterial activity. The variation of the refractive index of untreated PET/TiO2 fiber along its axis is studied. The computed tomography technique is used to investigate the morphology of the tested fiber and the distribution of TiO2 nanoparticles inside the fiber. The effect of stretching on the refractive index and the density of TiO2 nanoparticles of drawn PET/TiO2 fibers are carried out. The antimicrobial activity of the PET/TiO2 fibers are evaluated before and after stretching. The PET/TiO2 fibers are annealed at different temperatures and durations. The influence of annealing on the variation of the refractive index of PET/TiO2 fiber along its axis and the distribution of TiO2 is investigated.

Three-dimensional Measurements of Turbulent Ammonia Flames by Multi-Directional Schlieren CT (Computer Tomography) Technique

Three-dimensional Measurements of Turbulent Ammonia Flames by Multi-Directional Schlieren CT (Computer Tomography) Technique

Evaluation the Relationship between Mandibular Molar Root Apices and Mandibular Canal among Residents of the Moscow Population using Cone-Beam Computed Tomography Technique.

Background: The relationship between the inferior alveolar nerve and the root apices of the mandibular molars and premolars is of clinical importance. The aim of this study was to determine the relationship between the mandibular canal (MC) and the mandibular molar root apices using cone-beam computed tomography (CBCT) scanning among residents of the Moscow population.Materials and Methods: Three hundred CBCT scans for patients aged 20–70 years were analyzed. Patients were divided into three age groups: young group (20–44 years), middle-age group (45–59 years), and elderly group (60–70). The distance from the MC and the mandibular molar root apices was measured in each group in the coronal view of CBCT scans. Statistical analysis was set on P < 0.05.Results: The mean distance from the mesial root apices of the first, second, and third molars to the MC was 4.92, 2.85, and 2.24 mm, respectively. The distal root showed to be the closest root to the MC in multirooted teeth. The young age group showed smaller distances to MC than other age groups (P < 0.05). Females showed smaller distances to MC in mandibular molars than males (P < 0.05).Conclusions: The distance between the root apices and the MC has to be taken into consideration when performing surgical or endodontic procedures.

Simulating flow and heat transfer in a variety of diesel particulate filter porous structures using lattice Boltzmann method

Particulate matter has important influences on premature human mortality. Diesel particulate filter is one of the most effective means to reduce particulate matter in exhaust gas. In order to study the 3-D flow characteristics of diesel particulate filter porous structure, lattice Boltzmann method is used to study the flow and heat transfer characteristics of different structures. In some software, the spherical structure is used as diesel particulate filter porous structure. In paper, the spherical structure, the quartet structure generation set structure, and the computer tomography technique structure are constructed. The computer tomography technique structure is constructed by the serial sections of diesel particulate filter porous structure. The flow and heat transfer characteristics in different structures were simulated by lattice Boltzmann method. The 3-D computer tomography technique structure is constructed by superposing the serial section data of diesel particulate filter. The results show that the pressure gradient and temperature gradient of structures are greatly affected by the structure. The pressure gradient and temperature gradient of the spherical structure is the lowest. The spherical structure and the quartet structure generation set structure are different from the porous structure of diesel particulate filter in pressure gradient and temperature gradient. By comparing different structures, it can be seen that although the pressure gradients of the computer tomography technique structure and the quartet structure generation set structure are similar, the temperature gradient of the two structures are more different.