Use Of X-ray Computed Tomography Research Articles

Alpha-case promotes fatigue cracks initiation from the surface in heat treated Ti-6Al-4V fabricated by Laser Powder Bed Fusion

This research investigates the effect of the formation of an oxygen-stabilised titanium alpha layer – called alpha-case at the surface – on the fatigue properties of Ti-6Al-4V (Ti64) alloy components produced by Laser Powder Bed Fusion (L-PBF). Three post processing heat treatments with different controlled atmospheres were carried out on samples with as-built surfaces to evaluate how differences in alpha-case layer thickness and hardness affect the material’s susceptibility to surface embrittlement and its overall fatigue performance. The investigation includes bulk and subsurface microstructural analysis, surface characterisation by X-ray computed tomography (XCT), and fatigue testing. Key findings show that alpha-case layers can reduce the fatigue resistance of L-PBF fabricated Ti64. The presence of a 70±3 µm thick alpha-case layer was found to promote crack initiation. This is emphasised by a higher density of initiated cracks, thus leading to a reduction in fatigue life. Conversely, thinner alpha-case layers were found to have a reduced impact on the fatigue performance, highlighting the critical role of post processing heat treatments in modulating the fatigue resistance of the material. The use of XCT to characterise the surfaces of the specimens in 3D confirms that fatigue cracks primarily initiate at surface notches, highlighting the predominance of as-built surfaces over microstructure in determining the fatigue resistance of L-PBF Ti64 components.

Quantification of Thin Walls and Capsules Using X-Ray Computed Tomography

X-ray computed tomography (CT) is widely used in material science to understand the inner morphology of a specimen. Often, it is used to qualitatively understand the distribution of salient features such as cracks, voids, or particles. There are many challenges in using X-ray CT in a quantitative manner. These include a coarser resolution for comparable fields of view when compared to other imaging techniques (i.e., electron or optical microscopy), imaging artifacts (i.e., beam hardening and phase contrast), and the plethora of imaging and processing parameters that are chosen by the instrument/software user that can significantly affect the resultant measures. These limitations must be considered and quantified to acquire accurate and precise measurements. X-ray CT is powerful in that it can measure, in three dimensions, salient features that are subsurface and cannot be imaged with other direct line-of-sight imaging techniques. In this work, we discuss the use of X-ray CT to measure the thickness variations of thin walls of opacity capsules as well as the measurement of double-shell targets to understand the concentricity of the capsules within each other. Morphological measurements needed for target characterization require very high accuracy and precision. This paper will describe the application for the first time of a variety of measurements and will explore their robustness and pros and cons to identify areas of research to improve their accuracy and precision.

X-ray computed tomography for macropore analysis of cured and formed plates in lead acid batteries

When it comes to the properties of lead-acid batteries, macro porosity is seldom considered, even though it influences the active material loading, accessibility of acid into the active bulk material and the structural integrity of the plate. The porosity characteristics of positive and negative cured and formed plates were comprehensively analysed on the micro, meso and macro scale using a combination of BET N2 adsorption, mercury porosimetry and X-ray computed tomography (CT) respectively. Total porosity, pore size distribution, surface area, open and closed pores and surface-area-to-volume were included, where possible, with a plethora of additional data being obtained from X-ray CT analysis. Analysis from a single plate used in Starting, Lighting and Ignition (SLI) type batteries, which included three isolated samples per plate, revealed heterogeneity in macro-porosity across all regions analysed in the negative and positive cured and formed plates respectively. X-ray CT was further applied to thicker plates and a plate from an AGM type battery with a glass mat separator. The use of X-ray CT to study the changes in porosity characteristics can yield valuable insight into the properties of the active material since it remains intact within the grid support of a lead acid battery plate.

Processing of micro-CT images of granodiorite rock samples using convolutional neural networks (CNN), Part II: Semantic segmentation using a 2.5D CNN

X-ray computed tomography (XCT) is routinely used in geosciences for the purpose of rock characterisation. High-quality micro-CT images are successfully used for fracture characterisation, as well as analysis of grains and pores. In contrast, the use of XCT for mineral identification is uncommon and often ineffective. Implementation of micro-CT imaging techniques for mineral identification is affected by the accuracy and precision of the image segmentation results. Conventional segmentation methods such as thresholding, watershed, and active contouring are user-biased and do not provide the robust distinction between various heavy accessory minerals in granite rocks. Heavy ore minerals such as pyrite, chalcopyrite, molybdenite, and ilmenite are readily recognised in grey-scale micro-CT images because of their high attenuation coefficient, but further differentiation between these minerals using only traditional segmentation methods is challenging. Conversely, deep convolutional neural networks (CNNs) are fully self-trained, and they have demonstrated accurate semantic segmentation results for rock images. However, the application of CNN semantic segmentation for igneous rocks is not well documented. In this research, the U-Net 2.5D CNN was deployed to train the neural network on a combination of high-resolution micro-CT and mineral liberation analysis (MLA) images to identify different accessory mineral regions of interest (ROIs). The image segmentation results were assessed using MLA and SEM data, and the accuracy of segmentation was found to be greater than 97%. The methodology developed in this study can be extended to map the mineralogy of granite samples unseen by the CNN to further validate the robustness of the approach.

X-ray computed tomography, electron microscopy, and energy-dispersive X-ray spectroscopy of severed Zelkova serrata roots (Japanese elm tree)

X-ray computed tomography (XCT), field emission scanning electron microscopy (FESEM), and energy-dispersive X-ray spectroscopy (EDS) were evaluated for imaging and element identification of woody plant roots. Lateral roots of Japanese zelkova (Zelkova serrata) were severed in spring and maintained in soil for six months. The lateral roots were observed using XCT without maceration and sectioning. The general wood characteristics were discernible to reveal the bark and xylem structures in contrast-inverted tomograms. Virtual sections showed a newly formed ring of woundwood encircling the severed lateral roots. FESEM exhibited secondary xylem structures in which tyloses, fungal hyphae, and aggregates were present. While silicon was dispersed in and around the fungal hyphae, calcium was localized as distinct aggregates using EDS. These results suggest that the combined use of XCT, FESEM, and EDS has merit into the morphological assessment of tree health care, providing virtual sections, high-resolution images, and element composition from an entire woodblock.

Conformance and nonconformance in segmentation-free X-ray computed tomography geometric inspection

Additive Manufacturing (AM) is changing the manufacturing paradigm as it makes it possible to generate complex geometries that are impossible using conventional technologies. However, conventional GPS/GD&T practices are inadequate both at specifying and verifying geometric tolerances. In both cases, they lack the required flexibility. Applying volumetric instead of surface representations helps to solve the problem of specifying tolerances and coheres with topological optimization. The verification paradigm must be modified, too, as AM allows an increase in part complexity without a corresponding increase of cost. Among measurement techniques, only X-ray computed tomography (XCT), which is volumetric, is capable of easily measure complex parts. Leaving the discussion of volumetric tolerance specifications to the future, the aim of this work is exploring a part geometric accuracy verification by direct comparison between its nominal geometry and geometric tolerance volumetric representation, and an XCT volumetric image of it. Unlike the conventional use of XCT for geometric verification, this is a segmentation-free verification. The method is based on the “mutual information” of the two, i.e. information shared by the measured and nominal representations. The output is a conformance statement that does rely on a measurement but nor on a specific measured value not rely on a measurement result. This makes defining a decision rule considering consumer's and producer's risks difficult: uncertainty does not exist in this case. Statistic and simulation techniques make it possible to estimate these risks, defining a numerical model of the distribution of the gray values in a specific portion of the XCT image. Finally, an additive manufacturing case study validates the methodology.

A Study on the Use of XCT and FEA to Predict the Elastic Behavior of Additively Manufactured Parts of Cylindrical Geometry

Defining general criteria for the acceptability of defects within industrial components is often complicated, since the specific load conditions and the criticality of the given application should be considered individually. In order to minimize the risk of failure, high safety factors are commonly adopted during quality control. However this practice is likely to cause the rejection of components whose defects would be instead acceptable if a more sound knowledge of the component behaviour were achieved. Parts produced by additive manufacturing (AM) may suffer from various defects, including micro- or macro-holes, delamination and microstructural discontinuities. Such processes, which are specially suitable for one-off components, require robust and reliable inspection before a part is accepted or rejected, since the refusal of even a single part at the end of the production process represents a significant loss. For this reason, it would be very useful to simulate in a reliable way whether a certain defect is truly detrimental to the proper working of the part during operation or whether the component can still be used, despite the presence of a defect. To this purpose, the paper highlights the benefits of a synergistic interaction between Industrial X-ray computed tomography (XCT) and finite element analysis (FEA). Internal defects of additively manufactured parts can be identified in a non-destructive way by means of XCT. Then FEA can be performed on the XCT-based virtual model of the real component, rather than on the ideal CAD geometry. A proof of concept of this approach is proposed here for a reference construct produced in an Aluminium alloy by AM. Numerical results of the proposed combined XCT–FEA procedure are contrasted with experimental data from tensile tests. The findings sustain the reliability of the method and allow to assess its full provisional accuracy for parts of cylindrical geometry designed to operate in the elastic field. The paper moves a step beyond the present application limits of tomography as it is currently employed for AM parts and it evidences instead the possibility of extending the usage of tomography to acceptance testing and prediction of operative behaviour.

Micro-mechanical properties and multi-scaled pore structure of graphene oxide cement paste: Synergistic application of nanoindentation, X-ray computed tomography, and SEM-EDS analysis

In this study, the microstructure and micromechanical properties of graphene oxide (GO) cement-based materials are investigated. Nanoindentation with statistical deconvolution was used to determine the elastic properties of constituent phases. Besides, combined with scanning electron microscopy (SEM) equipped with energy-dispersive spectrometer (EDS) and backscattered electrons (BSE), each phase of hardened cement paste was identified and quantified as well. X-ray computed tomography (XCT) microscope was applied to determine the morphology of micrometer-size pores, while mercury intrusion porosimetry (MIP) was used to capture the volume fraction of smaller pores (nano-scale). The combined use of XCT and MIP offered an effective approach for further understanding the effect of GO on pore structure at multi-scale. The synergistic analysis of microstructure and micromechanical properties at multi-scale provides valuable information towards the material design of cement-based materials with nanomaterials.

Statistical validation of individual fibre segmentation from tomograms and microscopy

Imaging with X-ray computed tomography (CT) enables non-destructive 3D characterisations of the micro-structure inside fibre composites. In this paper we validate the use of X-ray CT coupled with image analysis for characterising unidirectional (UD) fibre composites. We compare X-ray CT at different resolutions to optical microscopy (OM) and scanning electron microscopy (SEM), where we characterise fibres by their diameters and positions. In addition to comparing individual fibre diameters, we also model their spatial distribution, and compare the obtained model parameters. Our study shows that X-ray CT is a high precision technique for characterising fibre composites and, with our suggested image analysis method for fibre detection, high precision is also obtained at low resolutions. This has great potential, since it allows larger fields of view to be analysed. Besides analysing representative volumes with high precision, we demonstrate that based on our methodology for individual fibre segmentation it is now possible to study complete bundles at the fibre scale and reveal inhomogeneities in the physical sample.

In-Situ Visualization of Multidimensional Imbibition in Dual-Porosity Carbonates

SummaryOil recovery by waterflood is usually small in fractured carbonates because of selective channeling of injected water through fractures toward producers, leaving much of the oil trapped in the matrix. One option to mitigate the low recovery is to reduce fracture uptake by increasing the viscosity of the injected fluids by use of polymers or foams. Another option, that is the objective of this work, is to inject surfactant solutions to reduce capillary effects responsible for trapping oil and allow gravity to segregate oil by buoyancy. Analysis of gravity and capillary forces suggests that such segregation is achievable in the laboratory, provided that cores are moderately long and oriented vertically. Besides investigating the role of gravity on oil recovery, the effect of surfactant-flood mode (secondary-flood mode and tertiary-flood mode) on the ultimate recovery (UR) was also investigated.To investigate the predictions of this analysis, coreflood experiments were conducted by use of carbonate cores and monitored by an X-ray computed-tomography (CT) scanner featuring true vertical positioning to quantify fluid saturation history in situ. Novel aspects of this work include cores that are oriented both horizontally and vertically to maximize gravitational effects as well as a special core holder that mimics aspects of fractured systems by use of the whole core. This paper discusses the contrast in experimental results in vertical and horizontal orientation with and without surfactant.To study gravity effects, surfactant reduced interfacial tension (IFT) from 40 to 3 mN/m. For this mode of recovery, ultralow IFT is not preferred because some capillary action is needed to aid injectant transport into the matrix. The vertical experiment showed that gravity has the potential of improving oil recovery at low IFT. Another surfactant was used to study the flood-mode effect; this surfactant reduced IFT from 40 to 0.001 mN/m (ultralow IFT). In this study, two experiments were conducted: a tertiary-surfactant-flood experiment and a secondary-surfactant-flood experiment. The secondary-flood experiment showed an improvement in recovery with the early implementation of the surfactant flood relative to the tertiary-flood experiment.This work highlights the importance of gravity at low IFT in terms of mobilizing trapped oil and also the effect of flood mode on UR. Moreover, this work emphasizes the use of surfactant solutions as a method of enhancing oil recovery in fractured resources not necessarily because of wettability alteration but mainly because of gravity effects. Experimental results are presented primarily as 1D and 3D reconstructions of in-situ oil- and water-phase saturation obtained by use of X-ray CT.

Relaxed Linearized Algorithms for Faster X-Ray CT Image Reconstruction.

Statistical image reconstruction (SIR) methods are studied extensively for X-ray computed tomography (CT) due to the potential of acquiring CT scans with reduced X-ray dose while maintaining image quality. However, the longer reconstruction time of SIR methods hinders their use in X-ray CT in practice. To accelerate statistical methods, many optimization techniques have been investigated. Over-relaxation is a common technique to speed up convergence of iterative algorithms. For instance, using a relaxation parameter that is close to two in alternating direction method of multipliers (ADMM) has been shown to speed up convergence significantly. This paper proposes a relaxed linearized augmented Lagrangian (AL) method that shows theoretical faster convergence rate with over-relaxation and applies the proposed relaxed linearized AL method to X-ray CT image reconstruction problems. Experimental results with both simulated and real CT scan data show that the proposed relaxed algorithm (with ordered-subsets [OS] acceleration) is about twice as fast as the existing unrelaxed fast algorithms, with negligible computation and memory overhead.

How little data is enough? Phase-diagram analysis of sparsity-regularized X-ray computed tomography.

We introduce phase-diagram analysis, a standard tool in compressed sensing (CS), to the X-ray computed tomography (CT) community as a systematic method for determining how few projections suffice for accurate sparsity-regularized reconstruction. In CS, a phase diagram is a convenient way to study and express certain theoretical relations between sparsity and sufficient sampling. We adapt phase-diagram analysis for empirical use in X-ray CT for which the same theoretical results do not hold. We demonstrate in three case studies the potential of phase-diagram analysis for providing quantitative answers to questions of undersampling. First, we demonstrate that there are cases where X-ray CT empirically performs comparably with a near-optimal CS strategy, namely taking measurements with Gaussian sensing matrices. Second, we show that, in contrast to what might have been anticipated, taking randomized CT measurements does not lead to improved performance compared with standard structured sampling patterns. Finally, we show preliminary results of how well phase-diagram analysis can predict the sufficient number of projections for accurately reconstructing a large-scale image of a given sparsity by means of total-variation regularization.

Development of a High Resolution X-Ray CT Technique for Irradiated Fuel Pellets

A nondestructive method making use of X-ray computer tomography (X-ray CT) has been applied to post irradiation examinations (PIEs) of fast breeder reactor (FBR) fuel assemblies. In the X-ray CT system, a 12 MeV X-ray pulse was used in synchronization with switching on the detector to minimize the effects of gamma ray emissions from the irradiated fuel assemblies. This technique enables a clear cross section CT images of the irradiated fuel assembly to be obtained.

Characterization of polymeric nonwovens using porosimetry, porometry and X-ray computed tomography

Abstract Removal of particles from gas and liquid streams is becoming increasingly important as a drive toward greater sustainability, the promise of resources recovery, and the regulatory environment create economic incentives to control water and air emissions. Membranes, and more specifically nonwovens, are commonly used for this purpose. Performance of nonwovens as filters is dependent on their pore structure (i.e. pore diameter, constricted pore size, and porosity). However, the characterization tools available for determining these structural metrics are underdeveloped for soft materials. In this study, several methods for evaluating pore size, pore diameter distribution, and porosity using polymeric nonwovens are investigated. Using both commercial polyester (PET) nonwovens and electrospun nanofibers, pore diameter distributions of nonwovens have been determined using two porosimetry techniques: mercury intrusion porosimetry (MIP) and liquid extrusion porosimetry (LEP). Analytical results from porosimetry were compared to porosity estimates obtained from X-ray computed tomography (XCT) images. The constricted pore size, or pore throat diameter, was also measured using porometry. In general, LEP resulted in higher measured porosities than MIP, likely due to compaction of the nonwoven in the latter. Electrospun materials exhibited similar or slightly lower porosities when compared to PET nonwovens, but their constricted pore diameters were orders of magnitude smaller due to smaller fiber sizes. The use of XCT was limited to the PET nonwovens due to limited resolution but it was shown to have potential for visualizing the 3-D structures of nonwovens and other polymeric materials.

Use of X-ray Tomography to Map Crystalline and Amorphous Phases in Frozen Biomaterials

The outcome of both cryopreservation and cryosurgical freezing applications is influenced by the concentration and type of the cryoprotective agent (CPA) or the cryodestructive agent (i.e., the chemical adjuvants referred to here as CDA) added prior to freezing. It also depends on the amount and type of crystalline, amorphous and/or eutectic phases formed during freezing which can differentially affect viability. This work describes the use of X-ray computer tomography (CT) for non-invasive, indirect determination of the phase, solute concentration and temperature within biomaterials (CPA, CDA loaded solutions and tissues) by X-ray attenuation before and after freezing. Specifically, this work focuses on establishing the feasibility of CT (100-420 kV acceleration voltage) to accurately measure the concentration of glycerol or salt as model CPA and CDAs in unfrozen solutions and tissues at 20 degrees C, or the phase in frozen solutions and tissue systems at -78.5 and -196 degrees C. The solutions are composed of water with physiological concentrations of NaCl (0.88% wt/wt) and DMEM (Dulbecco's Modified Eagle's Medium) with added glycerol (0-8 M). The tissue system is chosen as 3 mm thick porcine liver slices as well as 2 cm diameter cores which were either imaged fresh (3-4 h cold ischemia) or after loading with DMEM based glycerol solutions (0-8 M) for times ranging from hours to 7 days at 4 degrees C. The X-ray attenuation is reported in Hounsfield units (HU), a clinical measurement which normalizes X-ray attenuation values by the difference between those of water and air. NaCl solutions from 0 to 23.3% wt/wt (i.e. water to eutectic concentration) were found to linearly correspond to HU in a range from 0 to 155. At -196 degrees C the variation was from -80 to 95 HU while at -78.5 degrees C all readings were roughly 10 HU lower. At 20 degrees C NaCl and DMEM solutions with 0-8 M glycerol loading show a linear variation from 0 to 145 HU. After freezing to -78.5 degrees C the variation of the NaCl and DMEM solutions is more than twice as large between -90 and +190 HU and was distinctly non-linear above 6 M. After freezing to -196 degrees C the variation of the NaCl and DMEM solutions increased even further to -80 to +225 HU and was distinctly non-linear above 4 M, which after modeling the phase change and crystallization process is shown to correlate with an amorphous phase. In all tissue systems the HU readings were similar to solutions but higher by roughly 30 HU, as well as showing some deviations at 0 M after storage, probably due to tissue swelling. The standard deviations in all measurements were roughly 5 HU or below in all samples. In addition, two practical examples for CT use were demonstrated including: (1) glycerol loading and freezing of tissue cores and, (2) a mock cryosurgical procedure. In the loading experiment CT was able to measure the permeation of the glycerol into the sample at 20 degrees C, as well as the evolution of distinct amorphous vs. crystalline phases after freezing to -196 degrees C. In the mock cryosurgery example, the iceball edge was clearly visualized, and attempts to determine the temperature within the iceball are discussed. An added benefit of this work is that the density of these frozen samples, an essential property in measurement and modeling of thermal processes, was obtained in comparison to ice.

The use of X-ray computer tomography to investigate particulate interactions within opencast coal mine backfills

Restoration of opencast coal sites frequently involves the controlled compaction of heterogeneous arisings, and accurate prediction of the settlements associated with such backfill is difficult. Attention has previously focussed on improving the specifications used to control backfilling as a way of both reducing the magnitude of the settlements and improving their predictability. However, there still exists a large degree of uncertainty about the fundamental particulate interactions that occur within a fill. The range of mechanisms previously considered to be influential on creep behaviour is described. A current research programme is investigating the use of X-ray computer tomography (CT) as a means of nondestructively observing particle interactions during settlement, in conjunction with both long-term creep tests and short-term compressibility tests. The principles of this radiographic technique, which is relatively new to geotechnical engineering, are described, and findings are presented that illustrate the potential of the method. Interim findings indicate that large particles are distributed on an apparently random basis within a fill, and the nonuniform distribution of voids is clearly demonstrated. Moreover, the results presented conflict to some degree with the general consensus of opinion that particle crushing is a major mechanism in the settlement process. Rather, local collapse into small voids left by compaction, and relative sliding and rotation of particles, seem to be the dominant factors for a range of compaction efforts. Particle splitting is discernible on some sections, but this mechanism appears to be less significant than others. Research is continuing into the time dependency of the observed mechanisms, the effects of moisture content changes and the effects of heterogeneous initial particle strengths.

Application of X-Ray Computer Tomography for Observing the Deflection and Displacement of Fuel Pins in an Assembly Irradiated in FBR

A nondestructive method making use of X-ray computer tomography (X-ray CT) has been applied to post irradiation examination of fast breeder reactor (FBR) fuel assemblies. In the study, an examination is made of the deflection and displacement of fuel pin in a fuel assembly irradiated to 74.2GWd/t peak burnup in the fast reactor “JOYO.” In the examination, X-ray CT images of transverse cross sections of fuel pin were obtained at different heights of fuel pin along its axis. Analysis of the resulting images indicated that: 1. The hexagonal wrapper tube had its lateral wall faces slightly bulged outward; 2. The fuel pins loaded in the outermost array were markedly displaced in the direction of wrapper tube, particularly in portions of fuel pin intermediate between positions constrained by wrapping wire. The latter behavior of fuel pins was substantiated by the contours of fuel pin along its axis, which were derived from cross section images obtained at different levels along axis. Such fuel pin displacement is surmised to have been caused by thermal stressing of the affected fuel assembly cladding.

Application of X-Ray Computer Tomography for Observing the Deflection and Displacement of Fuel Pins in an Assembly Irradiated in FBR

A nondestructive method making use of X-ray computer tomography (X-ray CT) has been applied to post irradiation examination of fast breeder reactor (FBR) fuel assemblies. In the study, an examination is made of the deflection and displacement of fuel pin in a fuel assembly irradiated to 74.2GWd/t peak burnup in the fast reactor “JOYO.” In the examination, X-ray CT images of transverse cross sections of fuel pin were obtained at different heights of fuel pin along its axis. Analysis of the resulting images indicated that: 1. The hexagonal wrapper tube had its lateral wall faces slightly bulged outward;2. The fuel pins loaded in the outermost array were markedly displaced in the direction of wrapper tube, particularly in portions of fuel pin intermediate between positions constrained by wrapping wire. The latter behavior of fuel pins was substantiated by the contours of fuel pin along its axis, which were derived from cross section images obtained at different levels along axis. Such fuel pin displacement is surmised to have been caused by thermal stressing of the affected fuel assembly cladding.

The use of X-ray computer tomography for measuring the muscularity of live sheep

AbstractPotential measures of muscularity derived from X-ray computer tomography (CT) were assessed using data for 160 sheep (50 Suffolk males, 50 Suffolk females, 40 Texel males and 20 Charollais males). One-fifth of the lambs within each breed and sex were slaughtered at each of 14, 18 or 22 weeks of age and two-fifths slaughtered at 26 weeks. All lambs were CT scanned prior to slaughter with longitudinal and cross-sectional scans taken at three positions along the body [5th lumbar vertebra (LV5), mid-shaft of the femur (FEM) and ischium (ISC)]. After slaughter, linear measurements of side length (SL) and M. longissimus thoracis et lumborum (LTL) width (A) and depth (B) (12/ 13th thoracic vertebra) were taken on the left side of the carcass. The side was dissected and femur length (FL), the weight of three muscles surrounding the femur (M3) and the total muscle weight in the side (TM) were recorded. Five muscularity measures were calculated for the carcass. Two for the LTL muscle (A/SL, B/SL), one for the hind leg (√M3/FL3) and one for the whole carcass (√TM/SL3).Correlations between spine length measured on the CT longitudinal scans and side length measured on the carcass were high (> 0·62), while correlations between measurements of LTL width and depth on the carcass with those on the LV5 scan were moderate (> 0·41). CT measures of muscularity were derived using linear measurements taken on CT scans together with a prediction of total muscle weight using CT tissue areas. Correlations between CT measures and dissection measures of LTL and whole carcass muscularity were moderate to high (0·33–0·54). Correlations between the dissection measure and four CT measures of hind leg muscularity were higher (0·48-0·60). These results clearly show that good in vivo measures of muscularity can be obtained for sheep by using measurements that can be taken on CT scans. This will be a useful tool for selection programmes aiming to improve sheep carcass shape, particularly those already using CT scanning to increase rates of genetic improvement in lean tissue growth.

Use of x-ray computer tomography with intraenteric contrasting for differential diagnosis of ulcerative colitis and crohn disease

For the purpose of increasing informativity of X- ray methods in using them in the diagnosis of large intestine diseases including the differential diagnosis of nonspecific ulcerative colitis and Crohn disease 27 patients with the given diseases were examined using a modified method-computer tomography with intraenteric contrasting. The computer-tomographic sighus characteristic for colitis and Crohn dicease are established.