High-resolution X-ray Computed Tomography System Research Articles

High-resolution in situ characterization of micromechanisms in CFRP laminates under mode II loading

Micromechanisms in carbon fiber reinforced plastics (CFRPs) were studied by in situ mode II fracture toughness tests using a high-resolution optical microscope. The fracture toughness tests on four-point bend end notched flexure specimens were interrupted between the proportional limit and the plateau region, followed by postmortem examination using a high-resolution X-ray computed tomography system to identify three-dimensional microdamage. The observations sequentially captured the formation of damage zone, which composed of plastic zone, fiber/matrix debonding, and microcracks. The microscopic failure process was correlated with the macroscopic behavior of CFRP laminates during mode II fracture toughness tests.

Development of high-energy and high-resolution X-ray CT

This paper introduces a novel high-energy and high-resolution X-ray computed tomography system called eXTRACT. Preliminary experimental testing was performed of the penetration capability and structural resolution achieved by the system, and the results are reported. The X-ray source realized both bremsstrahlung X-rays with an average energy of 1 MeV and the focal size of 100 μm at the same time. Using 970 physical channels of high-energy X-ray line detectors and a modified offset scanning method, the CT reconstruction of 4286 by 4286 pixels were achieved for a single sinogram from a single fan beam scanning. The performance was further investigated by scanning several material standards. The penetration capability of 400 mm or more, represented by a longitudinal dimension of the object, was recorded in case of scanning aluminum. The structural resolution of 0.1 mm by 0.1 mm line and space structure under the field of view size of 300 mm in the diameter is also verified.

The Dynamic Fracture Process in Rocks Under High-Voltage Pulse Fragmentation

High-voltage pulse technology has been applied to rock excavation, liberation of microfossils, drilling of rocks, oil and water stimulation, cleaning castings, and recycling products like concrete and electrical appliances. In the field of rock mechanics, research interest has focused on the use of high-voltage pulse technology for drilling and cutting rocks over the past several decades. In the use of high-voltage pulse technology for drilling and cutting rocks, it is important to understand the fragmentation mechanism in rocks subjected to high-voltage discharge pulses to improve the effectiveness of drilling and cutting technologies. The process of drilling rocks using high-voltage discharge is employed because it generates electrical breakdown inside the rocks between the anode and cathode. In this study, seven rock types and a cement paste were electrically fractured using high-voltage pulse discharge to investigate their dielectric breakdown properties. The dielectric breakdown strengths of the samples were compared with their physical and mechanical properties. The samples with dielectric fractured were scanned using a high-resolution X-ray computed tomography system to observe the fracture formation associated with mineral constituents. The fracture patterns of the rock samples were analyzed using numerical simulation for high-voltage pulse-induced fragmentation that adopts the surface traction and internal body force conditions.

Analysis of intraindividual and intraspecific variation in semicircular canal dimensions using high‐resolution x‐ray computed tomography

The semicircular canal system tracks head rotation and provides sensory input for the reflexive stabilization of gaze and posture. The purpose of this study was to investigate the intraspecific and intraindividual variation in the size of the three semicircular canals. The right and left temporal bones were extracted from 31 individuals of the short-tailed shrew (Blarina brevicauda) and scanned on a high-resolution x-ray computed tomography system. The radius of curvature was calculated for each of the three semicircular canals for each side. Paired t-tests and independent sample t-tests indicated no significant differences in canal size between the right and left canals of the same individuals or between those of males and females of the same species. Pearson product moment correlation analyses demonstrated that there was no significant correlation between canal size and body mass in this sample.

Monte Carlo simulations of a high-resolution X-ray CT system for industrial applications

An X-ray computed tomography (CT) model based on the GEANT4 Monte Carlo code was developed for simulation of a cone-beam CT system for industrial applications. The full simulation of the X-ray tube, object, and area detector was considered. The model was validated through comparison with experimental measurements of different test objects. There is good agreement between the simulated and measured projections. To validate the model we reduced the beam aperture of the X-ray tube, using a source–collimator, to decrease the scattered radiation from the CT system structure and from the walls of the X-ray shielding room. The degradation of the image contrast using larger beam apertures is also shown. Thereafter, the CT model was used to calculate the spatial distribution and the magnitude of the scattered radiation from different objects. It has been assessed that the scatter-to-primary ratio (SPR) is below 5% for small aluminum objects (approx. 5 cm path length), and in the case of large aluminum objects (approx. 20 cm path length) it can reach up to a factor of 3 in the region corresponding to the maximum path length. Therefore, the scatter from the object significantly affects quantitative accuracy. The model was also used to evaluate the degradation of the image contrast due to the detector box.

X-ray Computed Tomography Image Analysis to explain the Airflow Resistance Differences in Grain Bulks

X-ray computed tomography (CT) is a technique that uses X-ray images to reconstruct the internal microstructure of objects. A high-resolution X-ray CT system with a resolution of 120 μm was used to scan slices of grain bulks. Grain bulks of wheat, barley, flax seed, peas and mustard were scanned along horizontal and vertical directions. The X-ray CT images were analysed to explain the airflow resistance difference along the horizontal and vertical directions of grain bulks. Total airspace, airpath distribution and size of airpaths were determined from the images. Morphological information of the airpaths from the tomographic images showed that the size and number of airpaths vary between horizontal and vertical directions of many grain bulks. Airpath area and airpath lengths along the horizontal direction were 100% higher than in the vertical direction for wheat, barley and flax seed bulks, where as for pea and mustard bulks, they were only 30% higher in the horizontal direction than in the vertical direction. The numbers of airpaths along the horizontal direction for wheat, barley and flax seed, respectively, were 92%, 145% and 187% more than along the vertical direction. In pea and mustard bulks, however the increase in the number of airpaths was only 28% and 17%. The ratio of total airspace area to the total number of airpaths in the grain bulk is the best predictor for the difference in the airflow resistance in horizontal and vertical directions in the grain bulk.

Validation of a high-resolution X-ray computed tomography system to measure murine adipose tissue depot mass in situ and longitudinally

Introduction: Obesity is a significant public health concern with considerable academic and industrial research effort underway to discover novel drugs to treat this disease. The aim of this study was to validate a recently developed high-resolution X-ray computed tomography (micro CT) system capable of measuring murine adipose tissue depot mass in situ. Methods: The micro CT was used to generate a series of cross-sectional X-ray images from which individual adipose tissue depot mass was quantified. Four individual adipose tissue depots were studied: inguinal subcutaneous, epididymal, retroperitoneal, and mesenteric. The relationship between micro CT-derived adipose tissue mass and adipose mass measured gravimetrically was determined. The effect of strain (C57/Bl6, C3H/HeNCR1BR, and db/db) and age (49 vs. 99 days) on adipose tissue depot mass was studied. Results: Validation studies in which adipose tissue depot mass was determined by micro CT and by gravimetry were conducted in the three strains of mice at 49 and 99 days of age. The correlation of micro CT and gravimetric measures of adipose tissue mass exceeded 90% in all strains at 99 days, and in the C57/Bl6 and C3H/HeNCR1BR strains at 49 days. At 49 days, the correlation in the db/db strain was 82%. Micro CT methodology distinguished both age and strain differences in the adipose tissue depots studied ( P<.0001, in all cases). Discussion: Micro CT is a valid method to quantify the mass of individual adipose tissue depots in mice. This method of determining adipose tissue mass is not a terminal procedure; thus, this methodology may be particularly useful for the longitudinal assessment of the effects of drug intervention on adipose tissue depot mass.

A new X-ray computed tomography system for laboratory mouse imaging

Two versions of a new high-resolution X-ray computed tomography system are being developed to screen mutagenized mice in the Oak Ridge National Laboratory Mammalian Genetics Research Facility. The first prototype employs a single-pixel CdZnTe detector with a pinhole collimator operating in pulse counting mode. The second version employs a phosphor screen/CCD detector operating in current mode. The major system hardware includes a low-energy X-ray tube, two linear translation stages and a rotational stage. For the single-pixel detector, image resolution is determined by the step size of the detector stage; preliminary images have been acquired at 100 /spl mu/m and 250 /spl mu/m resolutions. The resolution of the phosphor screen detector is determined by the modulation transfer function of the phosphor screen; images with resolutions approaching 50 /spl mu/m have been acquired. The system performance with the two detectors is described and recent images are presented.