X-ray micro-CT Imaging Research Articles

The Xerobranching Response Represses Lateral Root Formation When Roots Are Not in Contact With Water

Efficient soil exploration by roots represents an important target for crop improvement and food security [1, 2]. Lateral root (LR) formation is a key trait for optimising soil foraging for crucial resources such as water and nutrients. Here, we report a adaptive response termed xerobranching, exhibited by ceral roots, that represses branching when root tips are not in contact with wet soil. Non-invasive X-ray microCT imaging revealed that cereal roots rapidly repress LR formation as they enter an air space within a soil profile and are no longer in contact with water. Transcript profiling of cereal root tips revealed that transient water deficit triggers the ABA response pathway. In agreement with this, exogenous ABA treatment can mimic repression of LR formation under transient water deficit. Genetic analysis in Arabidopsis revealed that ABA repression of LR formation requires the PYR/PYL/RCAR-dependent signalling pathway. Our findings suggest that ABA acts as the key signal regulating xerobranching. We conclude that this new ABA-dependent adaptive mechanism allows roots to rapidly respond to changes in water availability in their local microenvironment and to use internal resources efficiently.

Injectable nanohydroxyapatite-chitosan-gelatin micro-scaffolds induce regeneration of knee subchondral bone lesions

Subchondral bone has been identified as an attractive target for KOA. To determine whether a minimally invasive micro-scaffolds could be used to induce regeneration of knee subchondral bone lesions, and to examine the protective effect of subchondral bone regeneration on upper cartilage, a ready-to-use injectable treatment with nanohydroxyapatite-chitosan-gelatin micro-scaffolds (HaCGMs) is proposed. Human-infrapatellar-fat-pad-derived adipose stem cells (IPFP-ASCs) were used as a cellular model to examine the osteo-inductivity and biocompatibility of HaCGMs, which were feasibly obtained with potency for multi-potential differentiations. Furthermore, a subchondral bone lesion model was developed to mimic the necrotic region removing performed by surgeons before sequestrectomy. HaCGMs were injected into the model to induce regeneration of subchondral bone. HaCGMs exhibited desirable swelling ratios, porosity, stiffness, and bioactivity and allowed cellular infiltration. Eight weeks after treatment, assessment via X-ray imaging, micro-CT imaging, and histological analysis revealed that rabbits treated with HaCGMs had better subchondral bone regeneration than those not treated. Interestingly, rabbits in the HaCGM treatment group also exhibited improved reservation of upper cartilage compared to those in other groups, as shown by safranin O-fast green staining. Present study provides an in-depth demonstration of injectable HaCGM-based regenerative therapy, which may provide an attractive alternative strategy for treating KOA.

Applying x-ray micro-tomography to learning and memory

Metabolic processes and neural pathways such as those for glucose metabolism and olfaction in insects are similar to, and in some cases identical to, those found in vertebrates. In particular, the peripheral architecture of the insect and mammalian olfactory system is surprisingly similar. Thus one insect, the western honeybee (Apis mellifera), has become a model organism for the investigation of olfactory signal processing in the brain. A. Mellifera has superior abilities to identify, classify, learn and remember odoriferous environmental chemicals. The use of x-ray MicroCT imaging for the non-invasive study of insects (termed diagnostic radioentomology ‘DR’) is increasing. This experiment was conducted as a ‘proof of principle’ study to identify whether DR scanning live insects (honeybees) can be used to non-invasively examine learning and memory with respect to brain architecture and function. A bench-top MicroCT scanner was used to scan live bees. To enhance tissue differentiation, radiographic contrast was injected directly into the haemolymph. Brain volume was measured using BeeView software. Gross brain architecture was visualised in 2D and 3D projections. Scanning of live bees enabled minimally-invasive imaging of physiological processes for the first time such as passage of contrast from gut to haemolymph as well as preliminary brain perfusion studies. In particular, the learning and memory neuropils in the antennal lobes were assessed by measuring changes in antennal lobe volumes. Future experiments will correlate neuropil volume changes with classic PER learning and memory studies. One advantage of using an insect model is that multiple experiments can be conducted without the need for lengthy ethics approvals that apply to vertebrate experiments. The advantage of using live insects is that longitudinal studies can be performed on individuals therefore reducing, to a great extent, the inherent inter-cohort errors which occur. Once proof of principles is established in the insect model, experiments such as these can easily be extended to vertebrates.

Visualization of xylem embolism by X‐ray microtomography: a direct test against hydraulic measurements

X-ray microtomography (microCT) is becoming a valuable noninvasive tool for advancing our understanding of plant-water relations. Laboratory-based microCT systems are becoming more affordable and provide better access than synchrotron facilities. However, some systems come at the cost of comparably lower signal quality and spatial resolution than synchrotron facilities. In this study, we evaluated laboratory-based X-ray microCT imaging as a tool to nondestructively analyse hydraulic vulnerability to drought-induced embolism in a woody plant species. We analysed the vulnerability to drought-induced embolism of benchtop-dehydrated Eucalyptus camaldulensis plants using microCT and hydraulic flow measurements on the same sample material, allowing us to directly compare the two methods. Additionally, we developed a quantitative procedure to improve microCT image analysis at limited resolution and accurately measure vessel lumens. Hydraulic measurements matched closely with microCT imaging of the current-year growth ring, with similar hydraulic conductivity and loss of conductivity due to xylem embolism. Optimized thresholding of vessel lumens during image analysis, based on a physiologically meaningful parameter (theoretical conductivity), allowed us to overcome common potential constraints of some lab-based systems. Our results indicate that estimates of vulnerability to embolism provided by microCT visualization agree well with those obtained from hydraulic measurements on the same sample material.

3D Pore-network quantitative analysis in deformed carbonate grainstones

This study consists of a three-dimensional (3D) assessment of the pore network properties (i.e., porosity, pore connectivity, specific surface area) in deformed carbonate grainstones cropping out in Sicily and Abruzzo regions (Italy). Previous studies, including microphotography, mercury injection analysis, and in-situ air permeameter measurements, have reported permeability differences (in the range of two-to-three orders of magnitude) between the carbonate grainstones exposed in Sicily and Abruzzo, that cannot be explained by only considering the differences of porosity. In this study, the pore network properties of suitable rock samples were studied by quantitative analysis of X-ray micro-CT images using both synchrotron and microfocus sources. On the basis of the results, inferences about the control of pore network properties on permeability were made for both host rock and deformation bands. In the host rocks, high values of connectivity seem to be associated with high values of permeability, whereas higher values of the specific surface area seem to correspond to lower permeability. Within the deformation bands (DBs), both porosity and pore connectivity are reduced except for local solution-enlarged stylolites and fractures (slip surfaces) preferentially connected parallel to the DB.

Direct scale comparison of numerical linear elastic moduli with acoustic experiments for carbonate rock X-ray CT scanned at multi-resolutions

Giant carbonate reservoirs hold almost 50–60% of the world's conventional hydrocarbons and are thus of major economic significance. The recently emerging Digital Rock Physics (DRP) based mechanical property predictions have been successful for sandstones when validated against laboratory results. For carbonates however the success has been limited due to their complex nature and heterogeneity. Typically experiments are conducted with core sample diameters in the order of several cm. Due to computational limitations numerical models are often of several orders of magnitude smaller than laboratory samples. In this study we used a standard carbonate rock called Silurian Dolomite to perform sonic wave experiments on two sample sizes: 1.5in. and 0.5in. diameter cylindrical cores. The latter unique size allowed us to compare our DRP based finite element method (FEM) simulations at a more compatible scale and higher image resolution. Through a multi-scale X-ray Micro-CT imaging of the same sample we studied the effect of resolution on elastic moduli simulation. We demonstrated the importance of determining Representative Volume Element (RVE) at each imaging resolution. Through determination of RVE as well as sampling of 40–55% volume fraction using non-overlapping cubes, we showed how our protocol leads to very satisfactory same scale validation of numerical linear elastic moduli predictions.

Geochemical anatomy of a spheroidally weathered diabase

Major, trace element concentrations and Nd, Sr isotope ratios were measured in micro-drilled samples of a 2.37Ga-old, hand-specimen sized spheroidally weathered diabase from southern India. A sample of the un-weathered diabase dike was also analyzed. X-ray micro-CT imaging of the weathered sample shows three dominant mineral phases which are plagioclase, pyroxene, and a Fe-bearing phase (possibly hematite and/or ilmenite). This imaging documents the pervasive nature of two generations of ribbon-like, cross-cutting fractures. The older fracture is sealed while the more recent fracture is open without any in-filling. The values of the Chemical Index of Alteration (CIA) of the samples show a wide range but are less than 50. Despite being a relatively less weathered rock, we observe that concentrations of major, minor and trace elements vary significantly with the percentage relative standard deviation (%RSD) for the elements ranging from 10.2–41.8. The CIA of the samples do not show any trend with the position of the sample in the hand-specimen. Barring Ca and Li, whose concentrations decrease from the core to the rim of the sample, there is no significant spatial trend in the concentrations of the elements.Concentrations of Na, Al, and Sr increase with increasing CIA values while concentrations of Mg, Fe, and Sc decrease with increasing CIA. The strong positive correlations of Na and Al, as well as Na and Sr indicates preferential weathering of plagioclase in the diabase. Na/Ca increases while Mg/Al, Mg/Na, Mg/Ca, Fe/Al and Sc/Sr decrease with increasing CIA values and the un-weathered rock plots in the middle of these trends. Such variations are explained in terms of differential weathering of plagioclase (in samples with lower CIA than the un-weathered rock, W1-type) and pyroxene (in samples with higher CIA than the un-weathered rock, W2-type) which have varying resistance to weathering. At the hand-specimen scale, the variability in the weathering indices like CIA are controlled by differential weathering of minerals and might not accurately reflect the intensity of weathering. Chondrite-normalized La/Sm and Gd/Lu co-vary with CIA values indicating mobility of the REEs during spheroidal weathering even at the hand-specimen scale. The Eu anomaly also increases with increasing CIA values which is explained by differential weathering of pyroxene and plagioclase. We observe large percentage deviations of the Nb-normalized concentrations of elements from the un-weathered rock in specific samples but no spatial trend is observed. Overall, the variations in element concentrations can be explained by varying fluid mobility of the elements, selective weathering of the minerals in the diabase, and ambient environmental conditions.Considerable Nd and Sr isotopic variability is observed at the hand-specimen scale and is explained in terms of weathering-related fractionation of parent/daughter ratios. This elemental fractionation must have happened long time ago to allow for radiogenic decay of the long-lived isotopes of 87Rb and 147Sm. The spread (%RSD) in the initial Sr and Nd isotope compositions of the weathered samples reach a minimum value around 1.2–1.3Ga which we interpret as the timing of the peak weathering event which led to fractionation of the parent/daughter ratios. For Nd isotopes, the average εNd (1.2Ga) of the weathered samples coincides with the εNd (1.2Ga) of the un-weathered rock. The timing of the weathering event coincides with the timing of the breakup of the Columbia supercontinent and follows wide-spread alkaline volcanism in the Indian subcontinent. This is the first such attempt to determine the timing of a weathering event in rocks using long-lived radioactive isotopes.

Synthesis of HA/β-TCP bioceramic foams from natural products

A novel technology for the preparation of bioceramic foams (BF) using a simple and economic procedure is presented. This technology combines two conventional methods to produce a tridimensional macroporous structure by using a sol–gel route, submitted afterward to a microwave treatment and thermal annealing. The use of agri-waste products on this procedure, such as egg shell and white egg recycle, represents an interesting way for waste management while developing potential commercial biomaterials. The use of egg shell as eco-compatible reactant instead of commercial ones and the egg white as foaming agent to produce a tridimensional macroporous structures has been optimized by using a sol–gel route. The crystalline phase and quantitative phase composition has been studied by Rietveld refinement and the optimization of the foaming process and determination of interconnected porosity by scanning electron microscopy, Hg porosimetry and X-ray micro-CT imaging. Our results show that BF samples showed a composition of 60 wt% HA (hydroxyapatite) and 40 wt% β-TCP (β-tricalcium phosphate) with a total porosity of approx. 70 % and a porosity ranging from 5 to 300 μm. These features indicate that BF samples are ideal for bone regeneration, and they are produced in an easy and environmental friendly viable process.

Dual-energy X-ray micro-CT imaging of hybrid Ni/Al open-cell foam

In this paper, we employ dual-energy X-ray microfocus tomography (DECT) measurement to develop high-resolution finite element (FE) models that can be used for the numerical assessment of the deformation behaviour of hybrid Ni/Al foam subjected to both quasi-static and dynamic compressive loading. Cubic samples of hybrid Ni/Al open-cell foam with an edge length of [15]mm were investigated by the DECT measurement. The material was prepared using AlSi7Mg0.3 aluminium foam with a mean pore size of [0.85]mm, coated with nanocrystalline nickel (crystallite size of approx. [50]nm) to form a surface layer with a theoretical thickness of [0.075]mm. CT imaging was carried out using state-of-the-art DSCT/DECT X-ray scanner developed at Centre of Excellence Telč. The device consists of a modular orthogonal assembly of two tube-detector imaging pairs, with an independent geometry setting and shared rotational stage mounted on a complex 16-axis CNC positioning system to enable unprecedented measurement variability for highly-detailed tomographical measurements. A sample of the metal foam was simultaneously irradiated using an XWT-240-SE reflection type X-ray tube and an XWT-160-TCHR transmission type X-ray tube. An enhanced dual-source sampling strategy was used for data acquisition. X-ray images were taken using XRD1622 large area GOS scintillator flat panel detectors with an active area of [410 × 410]mm and resolution [2048 × 2048]pixels. Tomographic scanning was performed in 1,200 projections with a 0.3 degree angular step to improve the accuracy of the generated models due to the very complex microstructure and high attenuation of the investigated material. Reconstructed data was processed using a dual-energy algorithm, and was used for the development of a 3D model and voxel model of the foam. The selected parameters of the models were compared with nominal parameters of the actual foam and showed good correlation.

The role of host rock properties in determining potential CO2 migration pathways

This work examines CO2⿿brine⿿cement⿿rock interactions and the associated permeability changes to understand the role of host rocks in determining CO2 migration pathways into groundwater aquifers under conditions relevant to geological carbon sequestration. Composite sandstone⿿cement and limestone⿿cement cores were used for an eight-day flow-through experiment. X-ray Micro-CT imaging revealed that CO2⿿brine⿿cement interaction predominated at the sandstone⿿cement interface, leading to a permeability increase by a factor of three. In the limestone⿿cement core, however, the CO2-rich flow diverted itself primarily into the higher permeability limestone, creating wormholes and a dominant flow path inside the limestone, resulting in a permeability increase by a factor of twenty four. Mass balance measurement indicates that the limestone⿿cement core lost about three times more of its original mass compared to the sandstone⿿cement core. These observations suggest differing CO2 migration pathways into underground drinking water resources through preferential pathways in host rocks.

C3-P-033-D cell geometrical analysis of epidermal and cortical cells in hypocotyl-root axes in arabidopsis seeds using X-ray micro-CT

Plants are composed of various types of cells. How these cells contribute to the overall body shape of plants is an important question in studies of plant development. Because plant cells are surrounded by rigid cell walls, newly formed cells are unable to migrate, and the geometrical relationships among neighboring cells are maintained for a long time during plant development. In arabidopsis (Arabidopsis thaliana (L.) Heynh. ecotype Columbia) seeds, one cortical cell layer exists between the epidermis and endodermis in the radicle, and two cortical cell layers are present in the hypocotyl. However, how the shape and geometry of these cells in the epidermis and cortex contribute to the embryo form remains unknown. We previously determined the three-dimensional (3-D) cell and tissue shapes and geometries in the embryo of an arabidopsis dry seed with X-ray micro computed tomography (micro-CT) using beamline BL20XU of SPring-8 synchrotron radiation facility [1]. In the present study, we constructed 3-D models of cell arrangement based on X-ray micro-CT images (8 keV, 0.2 μm/pixel) of whole seeds of arabidopsis, and analyzed the geometrical characteristics of epidermal and cortical cells. The size of the cross-sectional area of hypocotyl–root axis is largest in the proximal region of the hypocotyl, ~80 μm from the hypocotyl–root transition zone. Comparison between the cell division pattern and the change in cell size along the hypocotyl–root axis revealed that the increment in the lateral expansion of cortical cells contributed to the lateral expansion of the hypocotyl axis. In contrast, only the number of cell files, and not the size of cross-sectional area, increased when the area of epidermis increased. This work was partly supported by a grant from Hyogo Science and Technology Association. Experiments were performed with the approval of JASRI (Proposal nos 2012A1364 and 2014A1265). [1] D Yamauchi et al., AIP Conf. Proc. 1466 (2012) 237-242. C3-P-02 doi:10.1093/jmicro/dfv305

Examining the gastrointestinal transit of lipid-based liquid crystalline systems using whole-animal imaging.

Lipid-based liquid crystalline (LC) systems have the potential to sustain the oral absorption of poorly water-soluble drugs in vivo, facilitating slow drug release from their complex internal structure. To further evaluate the dynamic relationship between gastric retention and sustained drug absorption for these systems, this study aimed to explore non-invasive X-ray micro-CT imaging as an approach to assess gastric retention. Pharmacokinetic studies were also conducted with cinnarizine-loaded LC formulations to correlate gastric retention of the formulation to drug absorption. The in vivo studies demonstrated the interplay between gastric retention and drug absorption based on the digestibility of the LC structures. An increase in non-digestible phytantriol (PHY) composition in the formulation relative to digestible glyceryl monooleate (GMO) increased the gastric retention, with 68 ± 4% of formulation intensity remaining at 8h for 85% w/w PHY, and 26 ± 9% for 60% w/w PHY. Interestingly, it was found that PHY 30% w/w in GMO provided the highest bioavailability for cinnarizine (CZ) amongst the other combinations, including GMO alone. The studies demonstrated that combining digestible and non-digestible lipids into LC systems allowed for an optimal balance between sustaining drug absorption whilst increasing plasma concentration (C max) over time, leading to enhanced oral bioavailability. The results demonstrate the potential for utilising non-invasive X-ray micro-CT imaging to dynamically assess the GI transit of orally administered liquid crystal-forming formulations.

Effectiveness of Different Mechanical Methods on Dentin Caries Removal: Micro-CT and Digital Image Evaluation.

To determine the caries removal effectiveness (CRE) and minimal invasive potential (MIP) of caries excavation methods using digital imaging and microtomography analyses. Twelve human molars with occlusal caries lesions in dentin were randomly divided into three groups (carbide bur, exacavator, and polymer bur). They were sectioned mesiodistally, and standardized digital and computed microtomography x-ray (micro-CT) images were taken from each section before and after caries excavation. On each image, initial carious dentin (IC), prepared cavity (PC), and residual caries (RC) were defined according to visual criteria using ImageJ software. CRE was determined based on the RC/IC ratio, whereas MIP was determined by the PC/IC ratio. Data were analyzed using one-way analysis of variance and Student t-test or with Kruskal-Wallis and Student-Newman-Keuls test. The level of significance was set at 0.05. For both digital image and micro-CT analysis, the carbide bur showed higher CRE values than the excavator (p=0.0063 and p=0.0263, respectively) and the polymer bur (p=0.0028 and p=0.0005, respectively). The latter two presented similar results (p>0.05). Regarding MIP, for the digital image analysis, the polymer bur was different from the carbide bur (p=0.0030) but was not different from that of the excavator (p=0.1240). For micro-CT analysis, the MIP values of all the groups were significantly different, and the polymer bur was the most conservative method (p<0.05). The carbide bur was the most effective method for caries removal but was not completely conservative. The polymer bur and excavator presented low invasive potential but were not able to remove all of the carious dentin.

Abstract 4299: Comparison of high-resolution 3D X-ray microCT and tomosynthesis imaging: A breast phantom study

Abstract We have demonstrated the feasibility of imaging a mammographic accreditation phantom using high-resolution 3D X-ray microCT as an alternative to tomosynthesis. While both X-ray microCT and tomosynthesis produce high-resolution 3D images, tomosynthesis requires compression of the specimen and yields asymmetrical voxels, resulting in high spatial resolution along two axes and more limited resolution along the third axis. MicroCT imaging, however, does not require compression and provides uniform, high resolution in all directions. The limited angular range of tomosynthesis is advantageous for pre-operative screening tasks, while the increased spatial and full angular range of microCT has been increasingly applied to the assessment of surgically excised breast tissue during breast conserving surgery. Rapid and accurate assessment of excised tissues is desirable to minimize risk of recurrence, which is highest in the first two years after surgery. We employed a 35-80 kV, 7.6-15W scan protocol in X-ray microCT to image the breast phantom. We also tested the ability to detect the phantom target features (2.00-0.16 mm) in long (25 minute) and short (5-6 minute) scans. The phantom was designed to simulate the X-ray attenuation of a slab of compressed human breast consisting of glandular and adipose tissue. Both X-ray microCT and tomosynthesis were able to capture the smallest features (0.16 mm) of the phantom. Both long- and short-duration microCT scans enabled detection of the smallest (0.16mm) features of the phantom. The results obtained here suggest that (1) microCT could be used, as an alternative to tomosynthesis, to identify and localize features on the order of 100-200 microns in ex vivo tumor specimens and (2) microCT could be used to detect features of this size on an intra-operative basis (in 5-6 minute scans). This study shows the feasibility of using microCT for intra-operative 3D examination of surgical specimens, an application which could aid clinical decision-making in assessment of excision margins. Additionally, if high-resolution 3D imaging techniques can distinguish between features of tumor and non-tumor areas of tissues, as is suggested by these results, then these imaging modalities could hold promise for identification of biomarkers and elucidation of the gross anatomy of breast tumor types, such as ductal carcinoma in situ. There is not yet an accepted phantom for testing the detection limits of 3D high-resolution X-ray imaging. The phantom used here is a validated tool for calibration of mammography instruments, but it seems that digital X-ray imaging technologies, such as microCT, can quite easily capture the features of this phantom. Therefore, while microCT performed as well as tomosynthesis in detection of features in this breast phantom study, there is a need for the development and validation of new phantoms to assess the ability of tomosynthesis and microCT to resolve features in the &amp;lt;100 micron range. Citation Format: Jolene M. Singh, Anthony H. Bui, James S. Michaelson. Comparison of high-resolution 3D X-ray microCT and tomosynthesis imaging: A breast phantom study. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4299. doi:10.1158/1538-7445.AM2014-4299

Studying the morphology of lyophilized protein solids using X-ray micro-CT: effect of post-freeze annealing and controlled nucleation.

The objective of this study was to determine how different techniques used during the freezing step of lyophilization affect morphology of the dried protein solids. Aqueous solutions containing recombinant human albumin, trehalose, and sodium phosphate buffer were dried after their freezing by shelf-ramp cooling, immersion in liquid nitrogen, or controlled ice nucleation. Some shelf-frozen solutions were heat treated (annealed) before the vacuum drying. We used three-dimensional (3D) X-ray micro-computed tomography (micro-CT) and scanning electron microscopy (SEM) to study the morphology of solids. The X-ray micro-CT images of the lyophilized microporous solids showed traces of varied size and structure ice crystals that were comparable to corresponding SEM images. A post-freeze heat treatment and a controlled nucleation both induced larger ice crystal ghosts in the solids. The variations in the structure of walls surrounding ice crystals, formed by the different freezing procedures, should affect the water vapor transition during the primary and secondary drying. Some solids also showed higher-density layer in the upper surface. Overall, the simple sample preparation procedures and the ample morphological information make the X-ray micro-CT appropriate for analyzing lyophilized pharmaceuticals.

Preparation and osteogenic properties of magnesium calcium phosphate biocement scaffolds for bone regeneration

The regenerative treatment of large osseous defects remains a formidable challenge in today. In the present study, we have synthesized biodegradable magnesium calcium phosphate biocement (MCPB) scaffolds with interconnected macroporous structure (100–600 μm), as well as good bioactivity, biocompatibility and proper degradatibility. The results revealed that the porosity increased from 52% to 80% of MCPB scaffolds while the compressive strength decreased from 6.1 MPa to 1.2 MPa. We further assessed the effects of scaffolds on the rabbit femur cavity defect model in vivo by using synchrotron radiation X-ray microCT and microCT imaging, indicating that the MCPB scaffolds underwent gradually degradation and promoted the extensive neo-bone formation.

Stereological Analysis of Nonspherical Particles in Solid Metal

We review in this article the stereological theory of particles and perform stereological analysis of nonspherical TiB2 particles dispersed in solid aluminum. The two-dimensional (2D) particle size distribution (PSD) obtained from a projected area (PSDP) of TiB2 powder and the three-dimensional (3D) PSD based on the volume of particles were independently measured by optical microscopy and the electrical sensing zone method, respectively. The results obtained by the two methods were compared by transforming between them, using a fitted fractal dimension for the particles. The probability mass function of the cross-sectional areas (CSAs) of single nonspherical particles was measured by sectioning 3D reconstructions of particles obtained from a series of X-ray micro-CT images. The transformation from 3D PSD to 2D PSD according to the CSA (PSDC) was performed based on the stereological model. The inverse problem for the transformation from the 2D PSDC to 3D PSD is discussed.

Application of micro-computed tomography with iodine staining to cardiac imaging, segmentation, and computational model development.

Micro-computed tomography (micro-CT) has been widely used to generate high-resolution 3-D tissue images from small animals nondestructively, especially for mineralized skeletal tissues. However, its application to the analysis of soft cardiovascular tissues has been limited by poor inter-tissue contrast. Recent ex vivo studies have shown that contrast between muscular and connective tissue in micro-CT images can be enhanced by staining with iodine. In the present study, we apply this novel technique for imaging of cardiovascular structures in canine hearts. We optimize the method to obtain high-resolution X-ray micro-CT images of the canine atria and its distinctive regions-including the Bachmann's bundle, atrioventricular node, pulmonary arteries and veins-with clear inter-tissue contrast. The imaging results are used to reconstruct and segment the detailed 3-D geometry of the atria. Structure tensor analysis shows that the arrangement of atrial fibers can also be characterized using the enhanced micro-CT images, as iodine preferentially accumulates within the muscular fibers rather than in connective tissues. This novel technique can be particularly useful in nondestructive imaging of 3-D cardiac architectures from large animals and humans, due to the combination of relatively high speed ( ~ 1 h/per scan of the large canine heart) and high voxel resolution (36 μm) provided. In summary, contrast micro-CT facilitates fast and nondestructive imaging and segmenting of detailed 3-D cardiovascular geometries, as well as measuring fiber orientation, which are crucial in constructing biophysically detailed computational cardiac models.

3D porosity and mineralogy characterization in tight gas sandstones

Tight gas reservoirs exhibit storage and flow characteristics that are intimately tied to depositional and diagenetic processes. As a result, exploitation of these resources requires a comprehensive reservoir description and characterization program to identify properties which control production. In particular, tight gas reservoirs have significant primary and secondary porosity and pore connectivity dominated by clays and slot-like pores. This makes them particularly susceptible to the effects of overburden stress and variable water saturation. This paper describes an integrated approach to describe a tight gas sandstone at the pore scale in 3D. In particular, the primary and secondary porosity of a tight gas sandstone are identified and quantified in three dimensions using 3D X-ray micro-CT imaging and visualization of core material at the pore scale. 3D images allow one to map in detail the pore and grain structure and interconnectivity of primary and secondary porosity. Once the tomographic images are combined with SEM images from a single plane within the cubic data set, the nature of the secondary porosity can be determined and quantified. In-situ mineral maps measured on the same polished plane are used to identify different microporous phases contributing to the secondary porosity. Once these data sets are combined, the contribution of individual clay minerals to the microporosity, pore connectivity, and petrophysical response can be determined. Insight into the producibility may also be gained. This illustrates the role 3D imaging technology can play in a comprehensive reservoir characterization program for tight gas.

Compression deformation of a biaxial stitched glass fibre reinforcement: Visualisation and image analysis using X-ray micro-CT

The compression deformation response of glass fibre reinforcements is generally assumed to be non-linear elastic for the purposes of modelling. In some cases viscoelastic behaviour is also taken into account, while it is only more recently that permanent deformation is being considered. In a previous publication, the authors have showed that significant permanent deformation occurs, and is of comparable magnitude to elastic deformation. It is hypothesised here that permanent (and elastic) deformations in biaxial stitched fabric glass fibre reinforcement occur mainly by means of change of fibre bundle cross-sectional shape and size. Time-dependent deformation is thought to relate to fibre bundle displacement in the direction of compaction loading. Composite laminates were manufactured from a 820g/m2 biaxial stitched reinforcement material, using different processing parameters. Specimen pieces were cut from the laminates, and the deformation of fibre bundles in these specimens was studied employing X-ray micro-CT technology and image analysis software. The results demonstrate that fibre bundle cross-sections became thinner and elongated, more so under repeated compaction. Fibre bundles were also less undulated in the direction of loading with repeated compaction.