Computed Tomography Techniques Research Articles

Possible osteosarcoma reported from a new world elapid snake and review of reptilian bony tumors.

Cancer chiefly occurs in vertebrates. Rare in amphibians, and perhaps common in reptiles, various neoplasms and malignant cancers have been reported with erratic frequency by museums, paleontologists, veterinarians, and pet hobbyists. Unsurprisingly, most herpetofaunal diversity has never been systematically surveyed for the presence of neoplasms owing to the extreme rarity or obscurity of many species. Museum collections can fill these gaps in knowledge, especially when researchers use non-destructive techniques. In this study, we used X-ray computed tomography (CT) to discover and characterize a possible osteosarcoma of the spine in a rare South American coralsnake, Micrurus ancoralis. Two spinal vertebrae were completely fused and adjacent vertebrae showed evidence of corruption. The fused vertebrae contained a hollow inner network thought to be vascular tissue. We also review previous reports of neoplasms in the Elapidae and all bony neoplasms in non-avian reptiles. The rarely reported technique of X-ray CT for tumor discovery could greatly improve our understanding of the species diversity and perhaps underlying causes of neoplasia.

Low-dose CT of paediatric paranasal sinus using an ultra-low tube voltage (70 kVp) combined with the flash technique

To evaluate the radiation dose and diagnostic image quality of low-dose computed tomography (CT) of the paranasal sinus in children, with acquisition at an ultra-low tube voltage (70 kVp) combined with the Flash technique. Eighty paediatric patients underwent CT of the paranasal sinus and were divided into two groups according to different protocols (group A: 80 kVp protocol with conventional spiral mode [n=40] and group B: 70 kVp protocol with Flash scan mode [n=40]). For each examination, the CT dose index (CTDIvol), dose-length product (DLP), and effective dose (ED) were estimated. The image noise, signal-to-noise ratio (SNR), and overall subjective diagnostic image quality were also evaluated. For radiation dose, the CTDIvol (mGy), DLP (mGy·cm), and ED (mSv) values of the 70 kVp protocol were significantly lower than those of the 80 kVp protocol (CTDIvol: 1.57±0.009 versus 0.39±0.004 mGy, p<0.001; DLP: 19.88±2.01 versus 6.31±0.52 mGy·cm, p<0.001; ED: 0.079±0.016 versus 0.024±0.005 mSv, p<0.001). Compared with those of the 80-kVp protocol, the image noise increased by 40.7% (p=0.113), the SNRsoft-tissue decreased by 48.9%, and the SNRbone increased by 10.1% with the 70-kVp protocol (p=0.176 and 0.227, respectively). There was no significant difference in the overall subjective image quality grades between these two groups (p=0.15). When imaging the paranasal sinus in children, an ultra-low tube voltage (70 kVp) combined with the Flash CT technique can reduce the radiation dose significantly while maintaining diagnostic image quality with clinically acceptable image noise.

An experimental investigation on collapsible behavior of dry compacted phosphate mine waste rock in road embankment

Prescribing compaction at optimum water content in arid and semi-arid climate regions generally leads to unjustified ecological practices. Indeed, to achieve optimum densities for road embankment compaction, significant volumes of water are required, which is perceived as a very scarce resource in drought-prone areas. Dry compaction with the promotion of the use of materials at their natural moisture content can be a promising alternative that could save water resources. Nevertheless, dry compaction can affect the infrastructures’ stability under flooding conditions.This paper presents field and laboratory tests carried out to investigate the effect of dry compaction on Phosphate Mine Waste Rocks (PMWR) behavior. In situ tests were conducted and the PMWR dry compaction protocol has been defined. Furthermore, the collapse deformation and the shear strength properties were evaluated through double oedometer and triaxial tests, respectively. The microstructural evolution on wetting was evaluated using mercury intrusion porosimetry (MIP) and 3D X-Ray computed tomography techniques. The water retention curve and mineralogical quantification tools were used to explain the influence of hydraulic hysteresis and clay minerals properties on the hydro-geotechnical behavior of PMWR. The results show a significant effect of applied stress level and dry density in addition to the type and amount of clayey expansive minerals on the structural deformation of PMWR on wetting. PMWR showed a maximum collapse settlement of 5.33% under a pressure of 1500 kPa, while no collapse is expected for stress less than 100 kPa. Low content of clays was identified as well as the swelling shrinkage potential within PMWR. The ability of using PMWR as embankment materials at dry moisture content under total overburden stress below 200 kPa ensuring a dry density of at least 95%.σd max is confirmed. The results of this work can also be applied to standard materials with similar hydro-geotechnical characteristics.

Radiation exposure of computed tomography imaging for the assessment of acute stroke

PurposeTo assess suspected acute stroke, the computed tomography (CT) protocol contains a non-contrast CT (NCCT), a CT angiography (CTA), and a CT perfusion (CTP). Due to assumably high radiation doses of the complete protocol, the aim of this study is to examine radiation exposure and to establish diagnostic reference levels (DRLs).MethodsIn this retrospective study, dose data of 921 patients with initial CT imaging for suspected acute stroke and dose monitoring with a DICOM header–based tracking and monitoring software were analyzed. Between June 2017 and January 2020, 1655 CT scans were included, which were performed on three different modern multi-slice CT scanners, including 921 NCCT, 465 CTA, and 269 CTP scans. Radiation exposure was reported for CT dose index (CTDIvol) and dose-length product (DLP). DRLs were set at the 75th percentile of dose distribution.ResultsDRLs were assessed for each step (CTDIvol/DLP): NCCT 33.9 mGy/527.8 mGy cm and CTA 13.7 mGy/478.3 mGy cm. Radiation exposure of CTP was invariable and depended on CT device and its protocol settings with CTDIvol 124.9–258.2 mGy and DLP 1852.6–3044.3 mGy cm.ConclusionPerforming complementary CT techniques such as CTA and CTP for the assessment of acute stroke increases total radiation exposure. Hence, the revised DRLs for the complete protocol are required, where our local DRLs may help as benchmarks.

Simulations of single-shot X-ray phase-contrast tomography based on edge illumination

Single-shot X-ray phase-contrast imaging can simplify acquisition processes and reduce the dose delivered to a patient, and also reduce the imaging time, which increases the usability of the system for computed tomography (CT) and dynamic planar imaging. Edge illumination (EI) is a promising method of X-ray phase-contrast imaging that is expected to be implemented in compact devices using conventional X-ray sources. EI-based single-shot X-ray phase-contrast tomography (XPCT) has attracted much attention in recent years. Although single-shot XPCT is possible, further studies are needed before this method is translated into real-world applications. In this paper, a simulation model was built to study EI-baesd single-shot XPCT, including the main hardware conditions (such as the source, mask, detector, objects, and geometric conditions) and some key factors (such as photon statistics, X-ray spectrum, pixel crosstalk, and X-ray absorption). The extraction of information and reconstruction in the absorption, phase, and differential phase signals were implemented, and the effects of pixel crosstalk, photon statistics, and mask thickness on the imaging results were studied. The results suggest that XPCT has significant potential for improving imaging quality and reducing the radiation dose compared to traditional absorption-based CT techniques. The effects of pixel crosstalk are negligible when σc, the standard deviation of the Gaussian function, is much smaller than the detector pixel as a considerable top width remains in the pixel point spread function. Besides, a mask of considerable thickness is required to ensure the reconstruction accuracy of the quantitative information.

Neutron sub-micrometre tomography from scattering data.

Neutrons are valuable probes for various material samples across many areas of research. Neutron imaging typically has a spatial resolution of larger than 20 µm, whereas neutron scattering is sensitive to smaller features but does not provide a real-space image of the sample. A computed-tomography technique is demonstrated that uses neutron-scattering data to generate an image of a periodic sample with a spatial resolution of ∼300 nm. The achieved resolution is over an order of magnitude smaller than the resolution of other forms of neutron tomography. This method consists of measuring neutron diffraction using a double-crystal diffractometer as a function of sample rotation and then using a phase-retrieval algorithm followed by tomographic reconstruction to generate a map of the sample's scattering-length density. Topological features found in the reconstructions are confirmed with scanning electron micrographs. This technique should be applicable to any sample that generates clear neutron-diffraction patterns, including nanofabricated samples, biological membranes and magnetic materials, such as skyrmion lattices.

Influence of stack sequence on the mechanical characteristics of hybrid composites analyzed using cone beam computed tomography and scanning electron microscopy

AbstractThe hybridization of composites has recently seen an exponential growth in acceptance due to its ability to improve the property such as toughness of composites. Hybridization of fibers is known to give a better balance of properties and increases the opportunity to use natural fibers, thereby reducing the impact on the environment without compromising utility. This study deals with hybridization of ultrahigh‐molecular‐weight polyethylene (UHMWPE) with natural fibers such as flax and jute using phenol formaldehyde as the resin. Composite panels of 4 mm thickness, comprising of eight layers were fabricated in six different fiber stack sequences using hand lay‐up and compression molding techniques. The effect of stack sequence on the composites' flexural, interlaminar shear, and impact properties were investigated using scanning electron microscopy and cone beam computed tomography techniques. Composites with outer UHMWPE fibers and having flax fibers as inner core were found to have superior flexural and interlaminar shear properties of 44.45 and 5.52 MPa, respectively. Also composites with surface layers of flax fibers displayed maximum impact strength of 91.08 kJ/m2. The results indicate that the stack sequence has a significant influence on the properties of the composite under flexural and impact loading.

Soil quality indicators in areas with different vegetation cover in the Atlantic Forest biome, Southeastern Brazil

The southeast region of Brazil, in the Atlantic Forest biome, has been impacted for a long time, observing today small agricultural areas inserted in a matrix of pastures and forest fragments, the soils being highly modified due to the different forms of use they were submitted. The objective of this study was to evaluate the organic carbon content in the humic fractions on soil organic matter (SOM), the distribution of aggregates in size classes and the porosity and aggregates density variables by means of computed tomography in secondary forest, pasture and agriculture areas in Pinheiral (RJ). Three areas composed of secondary forests with different succession stages and three managed areas were evaluated: Secondary Forest (SF) Initial Stage (SFIS), Medium Stage (SFMS), Advanced Stage (SFAS), mixed managed pasture (MMP), and perennial and annual agriculture (PA and AA, respectively). Three types of samples were collected in different layers: i) deformed samples to quantify carbon in the SOM humic fractions; ii) clods for quantifying the mass of aggregates and later assessing the distribution by diameter classes; and iii) undisturbed samples collected with the aid of an acrylic cylinder to perform computed tomography (CT). Humic substances and aggregate classes below 2.0 mm were the attributes most influenced by the forms of use and/or vegetation cover. The CT technique proved to be efficient in the measurement of the edaphic attribute’s porosity and density of the aggregates, helping in the characterization and separation of the different environments.

Visualization of flow diverter stent wall apposition during intracranial aneurysm treatment using a virtually diluted cone beam CT technique (Vessel ASSIST)

Flow diverters (FD) have poor radiopacity, challenging visualization of deployment and vessel wall apposition with conventional neuroimaging modalities. We evaluated a novel cone beam computed tomography (CT) imaging technique that allows virtual dilution (VD) of contrast media to facilitate workflow and ensure accurate assessment of FD wall apposition. We retrospectively evaluated all patients treated for intracranial aneurysms with FD at our institution between November 2018 and November 2019. Undiluted injected dual cone beam CT acquisitions performed post-stenting were displayed with VD software (GE Healthcare). The resulting images were compared with conventional two-dimensional (2D) digital subtraction angiography (DSA) images. Two neurointerventionalists (Reader 1 and Reader 2, (R1, R2)) independently assessed FD deployment and wall apposition. Confidence in the diagnosis, inter-reader agreement, and X-ray exposure were assessed. A total of 27 cases were reviewed. FD deployment and wall apposition scores were 4.2 ± 1.0 (R1) and 4.0 ± 1.1 (R2) for DSA and 3.7 ± 1.2 (R1) and 4.1 ± 1.0 (R2) for VD. Confidence in the diagnosis was improved with VD, with scores of 3.7 ± 0.7 (R1) and 4.0 ± 0.7 (R2) using DSA and 4.9 ± 0.2 (R1) and 4.9 ± 0.2 (R2) using VD (P < 0.001). Inter-reader agreement using 2D DSA was improved from moderate (0.49324) to good (0.7272) (P < 0.0001). There were no significant differences in inter-reader agreement in the deployment assessment (P = 0.68) or dose-area product (P = 0.54) between techniques. VD imaging with dual cone beam CT enables accurate assessment of FD wall apposition after deployment with greater confidence and improved inter-reader agreement versus conventional 2D DSA alone, with comparable X-ray exposure.

ASSESSMENT OF SUSPICIOUS OVARIAN MASSES BY COMPARATIVE STUDY OF USG AND CT TECHNIQUES

Undoubtedly, most ovarian lesions, endometrial pathology and uterine lesions are best detected with ultrasound. Computed tomography (CT) imaging offers better diagnostic capabilities for large pelvic masses, tubo- ovarian abscesses, postoperative and postpartum complications. In some cases, Computed Tomography (CT) is employed to achieve optimal differential Diagnosis to determine the clinical pathway to follow. Hence based on above findings the present study was planned for Assessment of Suspicious Ovarian Masses by Comparative Study of USG and CT Techniques.&#x0D; The present study was planned in Department of Radio- Diagnosis, Katihar Medical College, Katihar (Al-Karim University), Bihar, India. In the present study 50 females were enrolled having Suspicious Ovarian Masses. Computed tomography (CT) and USG characteristics of different lesions were noted and recorded. The histopathological diagnosis was followed up and recorded. The results of this study were analysed and compared with other available studies in literature.&#x0D; The data generated from the present study concludes that Ultrasonography is usually the first imaging modality in evaluation of female patients suspected to have pelvic pathology. Computed tomography is superior diagnostic imaging modality than USG prior to treatment which improved detection and characterization of tumour due to better diagnostic accuracy and consequently reduction of invasive procedure which lead to significant reduction of mortality and morbidity from tumour.&#x0D; Keywords: Ovarian Masses, Comparative Study, USG, CT Techniques, etc.

Functional CT Contrast Nanoagents for the Tumor Microenvironment

Understanding the detailed tumor microenvironment (TME) is essential to achieve effective treatment of tumor, because TME has an extremely profound influence on the occurrence, development, invasion, and metastasis of tumor. It is of great significance to realize accurate diagnosis of the TME by using functional computed tomography (CT) contrast nanoagents (FCTNAs). Here, an overview of FCTNAs that respond to the overexpressed receptors, acidic microenvironment, overexpressed glutathione and enzymes, and hypoxia in tumor is provided, and also prospects the advance of novel spectral CT technique to detect the TME precisely. Utilizing FCTNAs is expected to achieve accurate monitoring of the TME and further provide guidance for the effective personalized tumor treatment in clinic.

Fiber Orientation Distribution Predictions for an Injection Molded Venturi-Shaped Part Validated Against Experimental Micro-Computed Tomography Characterization

Fil: Quintana, Maria Camila. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnologia de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingenieria. Instituto de Investigaciones en Ciencia y Tecnologia de Materiales; Argentina

Understanding pore formation and the effect on mechanical properties of High Speed Sintered polyamide-12 parts: A focus on energy input

High Speed Sintering is a novel powder-bed fusion Additive Manufacturing technique that uses an infrared lamp to provide intensive thermal energy to sinter polymer powders. The amount of thermal energy is critical to particle coalescence related defects such as porosity. This study investigates the effect of energy input on porosity and the resulting mechanical properties of polyamide-12 parts. Samples were produced at different lamp speeds, generating varying amount of energy input from a low to a high level. They were then scanned using X-ray Computed Tomography technique, following which they were subject to tensile testing. A strong correlation between energy input, porosity and mechanical properties was found, whereby pore formation was fundamentally caused by insufficient energy input. A greater amount of energy input resulted in a reduced porosity level, which in turn led to improved mechanical properties. The porosity, ultimate tensile strength and elongation achieved were 0.58%, 42.4 MPa and 10.0%, respectively, by using the standard parameters. Further increasing the energy input resulted in the lowest porosity of 0.14% and the highest ultimate tensile strength and elongation of 44.4 MPa and 13.5%, respectively. Pore morphology, volume, number density and spatial distribution were investigated, which were found to be closely linked with energy input and mechanical properties.

Analysis of Error in Convolution Algorithm for Tomography in Discrete Spaces

In this paper simulation results of the error in computed tomography technique for discrete space is presented. In computerized tomography, due to ill posed and non-linear nature of reconstruction algorithms, the efficient algorithms are required for both medical and industry process. The error analysis for approximation algorithms of computerized tomography is necessary to check the efficiency of algorithm. The filter function for algorithm with some moments properties are already known. The use of same bandlimited filter with different number of rays in each projection data leads to different reconstruction and approximation nature of algorithm arises error in the implementation. The results of our theorem for different values are found to be compared with classic convolution back-projection algorithm.

CT Imaging of Left Ventricular Assist Devices and Associated Complications

The purpose of this paper is to review the current role of computed tomography (CT) in the imaging of left ventricular assist devices (LVAD). Recent studies have highlighted the prognostic role of measuring skeletal muscle CT attenuation in predicting adverse LVAD outcomes. CT is also useful for evaluation of inflow cannula malposition, and outflow graft complications such as obstruction and kinking. In addition, 18F-fluorodeoxyglucose positron emission tomography-computed tomography (FDG PET-CT) has been shown to be of value in evaluation of suspected LVAD infection. Newer CT techniques such as dual-energy CT and metal artifact reduction algorithms can potentially generate better quality CT images, though currently there is no high-quality published literature on their use in LVAD imaging. CT is a useful technique as part of a multi-modality approach in the evaluation of LVADs and associated complications.

Data-driven three-dimensional super-resolution imaging of a turbulent jet flame using a generative adversarial network.

Three-dimensional (3D) computed tomography (CT) is becoming a well-established tool for turbulent combustion diagnostics. However, the 3D CT technique suffers from contradictory demands of spatial resolution and domain size. This work therefore reports a data-driven 3D super-resolution approach to enhance the spatial resolution by two times along each spatial direction. The approach, named 3D super-resolution generative adversarial network (3D-SR-GAN), builds a generator and a discriminator network to learn the topographic information and infer high-resolution 3D turbulent flame structure with a given low-resolution counterpart. This work uses numerically simulated 3D turbulent jet flame structures as training data to update model parameters of the GAN network. Extensive performance evaluations are then conducted to show the superiority of the proposed 3D-SR-GAN network, compared with other direct interpolation methods. The results show that a convincing super-resolution (SR) operation with the overall error of ∼4% and the peak signal-to-noise ratio of 37 dB can be reached with an upscaling factor of 2, representing an eight times enhancement of the total voxel number. Moreover, the trained network can predict the SR structure of the jet flame with a different Reynolds number without retraining the network parameters.

Characterisation and correlation of areal surface texture with processing parameters and porosity of High Speed Sintered parts

High Speed Sintering is an advanced powder bed fusion polymer Additive Manufacturing technique aimed at economical production of end-use parts in series manufacture. Surface finish is thus of high importance to end users. This study investigates the surface topography of High Speed Sintered parts produced using a range of different energy-related process parameters including sinter speed, lamp power and ink grey level. Areal surface texture was measured using Focus Variation microscopy and the sample porosity was systematically examined by the X-ray Computed Tomography technique. Surface topography was further characterised by Scanning Electron Microscopy, following which the samples were subject to tensile testing. Results showed that areal surface texture is strongly correlated with porosity, which can be further linked with mechanical properties. Certain texture parameters i.e. arithmetic mean height Sa, root-mean-square Sq and maximum valley depth Sv were identified as good indicators that can be used to compare porosity and/or mechanical properties between different samples, as well as distinguish up-, down-skins and side surfaces. Sa, Sq and Sv for up- and down-skins were found to correlate with the above energy-related process parameters. It was also revealed that skewness Ssk and kurtosis Sku are related to sphere-like protrusions, sub-surface porosity and re-entrant features. Energy input is the fundamental reason that causes varying porosity levels and consequently different surface topographies and mechanical properties, with a 10.07 μm and a 30.21 % difference in Sa and porosity, respectively, between the ‘low’ and ‘high’ energy input.

Correlation between computed tomography volumetry and nuclear medicine split renal function in live kidney donation: a single-centre experience.

Potential live renal donors undergo both renal computed tomography angiogram (CTA) and nuclear imaging dimercaptosuccinic acid (DMSA) scans. Each kidney's renal function and vascular anatomy influences the choice of donor side. Although DMSA measures differential blood flow, it is a surrogate for renal function and nephron mass. Computed tomography techniques can provide volumetry information. The aim of this study was to determine the relationship between measured split renal volumes on computed tomography versus renal volumes derived from DMSA split function in live donors. Prospective data of live kidney donors assessed at a single Australian centre from 2014 to 2017 were reviewed. All patients had pre-operative CTA and DMSA imaging. Renal volume was determined via semi-automated software calculation from CTA three-dimensional image reconstructions by one investigator. Measured split renal volume was compared against calculated renal volume using measured DMSA split function (percentage split function multiplied by total renal volume). Fifty-three patients were included in the study. Split renal volumes on three-dimensional CTA images correlate to calculated split volumes determined from DMSA (Pearson coefficient 0.95 for right renal volume, 0.95 for left). The decision of which kidney to remove can be achieved with CTA only. Omitting a DMSA scan would reduce the radiation load by 0.70 mSv (35 chest X-rays) and potential cost saving of AU$1062.00 per donor. CTA technology allows accurate assessment of renal volumes that correlate well with DMSA split function. Avoiding a DMSA scan results in cost and radiation reduction in the assessment of a live kidney donor.

Development of a microstructure-based numerical approach for analyzing heat transfer within the asphalt mixture

Computed Tomography technique has been commonly used to obtain the geometric model of asphalt mixture for the microstructure-based heat transfer numerical analysis. However, this technique relies on expansive equipment and has shortcomings related to limited sample size and difficulty in identifying the boundary of stones. This study proposes a cost and time-effective numerical method to compute the heat transfer within asphalt mixture from the microstructure point of view. The computer graphics technique is adopted to develop the geometric model of asphalt mixture, including coarse stones and asphalt matrix. The generated geometric model is imported into the finite element software to compute the thermal conductivity and specific heat capacity of asphalt mixture. To obtain input parameters of the newly developed numerical method, the thermal conductivity and specific heat capacity of coarse stones and asphalt matrix are measured through the heat plate exchanger. The above two parameters of asphalt mixture are also measured to verify the computed results by the newly developed numerical method. The differences between computed and measured thermal conductivity and specific heat capacity of asphalt mixture are 9.0% and 8.6% respectively, indicating a good performance of the newly proposed microstructure-based numerical approach. On the other hand, computed results show that asphalt mixtures with different sample sizes and aggregate size distributions have non-uniform distributions of heat flux and temperature, mainly due to the different thermo-physical properties between coarse stone and asphalt matrix. For asphalt mixtures, a knowledge of heat flux and temperature fluctuations from the microstructure point of view may shed light on the analysis of stress/strain distribution and crack propagation in asphalt mixture.

Computed tomography for in vivo deep over-1000 nm near-infrared fluorescence imaging.

This study aims to develop a novel cross-sectional imaging of fluorescence in over-1000 nm near-infrared (OTN-NIR), which allows in vivo deep imaging, using computed tomography (CT) system. Cylindrical specimens of composite of OTN-NIR fluorophore, NaGdF4 co-doped with Yb3+ and Ho3+ (ex: 980 nm, em: 1150 nm), were embedded in cubic agar (10.5-12 mm) or in the peritoneal cavity of mice and placed on a rotatable stage. When the fluorescence from inside of the samples was serially captured from multiple angles, the images were disrupted by the reflection and refraction of emitted light on the sample-air interface. Immersing the sample into water filled in a rectangular bath suppressed the disruption at the interface and successfully reconstructed the position and concentration of OTN-NIR fluorophores on the cross-sectional images using a CT technique. This is promising as a novel three-dimensional imaging technique for OTN-NIR fluorescent image projections of small animals captured from multiple angles.