nano-CT Imaging Research Articles

A novel multimodular methodology to investigate external cervical tooth resorption

To introduce a multimodular combination of techniques as a novel minimal invasive approach to investigate efficiently and accurately external cervical resorption (ECR). One case of a central incisor with extensive external cervical resorption was selected to demonstrate the potential of a comparative novel study methodology. ECR diagnosis was based on clinical inspection, digital radiography and cone-beam computed tomography (CBCT). After extraction, the tooth was investigated using microfocus computed tomography (micro-CT), nano-CT and hard tissue histology. These techniques were compared for their accuracy and applicability to highlight their advantages and disadvantages. Nano-CT was more effective than micro-CT and CBCT for detailed ex vivo exploration of ECR. The reparative tissue, pericanalar resorption resistant sheet (PRRS), pulp tissue reactions, resorption channels and their interconnection with the periodontal ligament space were accurately visualized by detailed processing and analysis of the nano-CT data set with Dataviewer and CTAn software. Nano-CT analysis provided better insight in the true extent of the resorption, based on quantitative measurements and 3D visualization of the tooth structure. Nano-CT imaging results were similar to hard tissue histology at the mineralized tissue level. To clarify the dynamic phenomenon of reparative tissue formation and substitution of the resorbed tissues, nano-CT needed to be associated with hard tissue histology. Nano-CT is a fast and minimal invasive technique for the ex vivo analysis and understanding of ECR and is complementary with hard tissue histology. A combined approach of clinical and CBCT examination, with nano-CT and histological mapping measurements, can provide an ideal platform for future ECR imaging and exploration studies.

A user-friendly nano-CT image alignment and 3D reconstruction platform based on LabVIEW

X-ray computed tomography at the nanometer scale (nano-CT) offers a wide range of applications in scientific and industrial areas. Here we describe a reliable, user-friendly, and fast software package based on LabVIEW that may allow us to perform all procedures after the acquisition of raw projection images in order to obtain the inner structure of the investigated sample. A suitable image alignment process to address misalignment problems among image series due to mechanical manufacturing errors, thermal expansion, and other external factors has been considered, together with a novel fast parallel beam 3D reconstruction procedure that was developed ad hoc to perform the tomographic reconstruction. We have obtained remarkably improved reconstruction results at the Beijing Synchrotron Radiation Facility after the image calibration, the fundamental role of this image alignment procedure was confirmed, which minimizes the unwanted blurs and additional streaking artifacts that are always present in reconstructed slices. Moreover, this nano-CT image alignment and its associated 3D reconstruction procedure are fully based on LabVIEW routines, significantly reducing the data post-processing cycle, thus making the activity of the users faster and easier during experimental runs.

Modeling Hierarchical Non-Precious Metal Catalyst Cathodes for PEFCs Using Multi-Scale X-ray CT Imaging

This paper reports the development of a model for simulating polymer electrolyte fuel cells (PEFCs) with non-precious metal catalyst (NPMC) cathodes. NPMCs present an opportunity to dramatically reduce the cost of PEFC electrodes by removing the costly Pt catalyst. To address the significant transport losses in thick NPMC cathodes (ca. >60 µm), we developed a hierarchical electrode model that resolves the unique structure of the NPMCs we studied. A unique feature of the approach is the integration of the model with morphology data extracted from nano-scale resolution X-ray computed tomography (nano-CT) imaging of the electrodes. A notable finding is the impact of the liquid water accumulation in the electrode and the significant performance improvement possible if electrode flooding is mitigated.

A review of the microgastropod genus Systenostoma Bavay & Dautzenberg, 1908 and a new subterranean species from China (Gastropoda, Pulmonata, Hypselostomatidae).

A review of the microgastropod genus Systenostoma is provided. Thai and Malaysian species are transferred to a new genus, Angustopila (type species: Systenostoma tamlod Panha & Burch, 1999). A new subterranean Angustopila species is described here. Conchologically, the new species is most similar to the cave-dwelling, Thai A. tamlod (Panha & Burch, 1999). One Thai species (Systenostoma edentata) is transferred to the genus Hypselostoma. Vietnamese members remain in the genus Tonkinospira (nomen novum) for Systenostoma Bavay & Dautzenberg, 1908 (non Systenostoma Marsson, 1887). A comprehensive map of former Systenostoma species is presented. SEM and NanoCT images, including a video of A. huoyani sp. n. internal shell morphology, provide novel perspectives of the shells of Angustopila and of the scarcely known Vietnamese Tonkinospira species. The biology of these snails is not yet known but collection localities suggest a troglophilic ecology.

Bone canalicular network segmentation in 3D nano-CT images through geodesic voting and image tessellation

Recent studies emphasized the role of the bone lacuno-canalicular network (LCN) in the understanding of bone diseases such as osteoporosis. However, suitable methods to investigate this structure are lacking. The aim of this paper is to introduce a methodology to segment the LCN from three-dimensional (3D) synchrotron radiation nano-CT images. Segmentation of such structures is challenging due to several factors such as limited contrast and signal-to-noise ratio, partial volume effects and huge number of data that needs to be processed, which restrains user interaction. We use an approach based on minimum-cost paths and geodesic voting, for which we propose a fully automatic initialization scheme based on a tessellation of the image domain. The centroids of pre-segmented lacunæ are used as Voronoi-tessellation seeds and as start-points of a fast-marching front propagation, whereas the end-points are distributed in the vicinity of each Voronoi-region boundary. This initialization scheme was devised to cope with complex biological structures involving cells interconnected by multiple thread-like, branching processes, while the seminal geodesic-voting method only copes with tree-like structures. Our method has been assessed quantitatively on phantom data and qualitatively on real datasets, demonstrating its feasibility. To the best of our knowledge, presented 3D renderings of lacunæ interconnected by their canaliculi were achieved for the first time.

Experimental study into the fundamental understanding of blending between reclaimed asphalt binder and virgin bitumen using nanoindentation and nano-computed tomography

The properties of asphalt mixtures containing a high amount of reclaimed asphalt are presumed to be strongly influenced by the degree of blending between old and virgin bitumen. As part of a PhD project, fundamental testing at micro- and nano-levels was undertaken to achieve better understanding of the blending and diffusion phenomenon between rheologically and chemically different bitumens. Three different techniques were used to observe the interface zones of bitumen–bitumen and aggregate–bitumen zones. Nanoindentation, nano-computed tomography (nano-CT) scanning and optical microscopy were done on three different groups of prepared samples. Nanoindentation was conducted to evaluate the difference of surface stiffness of aggregate binder interfaces. Nano-CT scanning techniques were used to observe slight differences in density of the interface in binder zones. Optical microscopy was conducted on thin sections of an asphalt mixture to detect the interface zone between two binders. With nano-CT scanning, it is possible to see the separation zone between the hard- and soft-grade bitumen. Nano-CT scanning images on two different bitumens clearly showed the two bitumen layers due to their varying densities but it was not possible to detect two different binders inside the mixture. Initial results from the nanoindentation study illustrated the benefit of using nanoindentation in detecting two different binders. It was not possible to detect hard and soft bitumens from optical microscopy images on thin sections. Differences in enhanced colours in some points were caused by their difference in thickness. The three-dimensional analysis of bitumen nano-CT images seems to be in reasonable agreement with the assumed bitumen microstructure but further research is needed to confirm this.

Thalidomide influences atherogenesis in aortas of ApoE−/−/LDLR−/− double knockout mice: a nano-CT study

Plaque progression in atherosclerosis is closely connected to angiogenesis due to vasa vasorum (VV) growth. Objective of this study was to determine the unknown long-term effect of thalidomide on adventitial VV neovascularization and plaque progression using nano-focussed computed tomography (nano-CT). Proliferation and migration assays in human coronary artery endothelial cells (HCAEC) measured number of viable cells after incubation with thalidomide. Male ApoE−/−/LDLR−/− (AL) mice (n = 5) received a thalidomide containing western diet (WD) over 29 weeks. Another five male AL mice (WD without thalidomide) served as control group. Descending aortas were scanned with nano-CT at (1.5 μm)3 isotropic voxel size. Number and area of adventitial VV as well as plaque cross sectional area were measured. Results were complemented by histology. Thalidomide inhibited proliferation and migration of HCAEC dose-dependently. VV neovascularization decreased in number per cross section (7.66 ± 0.301 vs. 8.62 ± 0.164, p < 0.001) and in cross sectional area (0.0183 ± 0.0011 vs. 0.0238 ± 0.0008 mm2, p < 0.001). Cross sectional area of plaque decreased significantly when treated with thalidomide (0.57 ± 0.0187 vs. 0.803 ± 0.0148 mm2, p < 0.001). Nano-CT imaging revealed a reduced plaque growth and VV neovascularization after long-term application of thalidomide. Therefore, nano-CT can be considered as a new method to detect therapeutic effects in experimental models of atherosclerosis.

In situ investigation of the 3D mechanical microstructure at nanoscale: nano-CT imaging method of local small region in large scale sample.

To investigate the local micro-/nanoscale region in a large scale sample, an image reconstruction method for nanometer computed tomography (nano-CT) was proposed in this paper. In the algorithm, wavelets were used to localize the filtered-backprojection (FBP) algorithm because of its space-frequency localization property. After the implementation of the algorithm, two simulation local reconstruction experiments were performed to confirm its effectiveness. Three evaluation criteria were used in the experiments to judge the quality of the reconstructed images. The experimental results showed that the algorithm proposed in this paper performed best because (1) the quality of its results had improved 20%–30% compared to the results of FBP and 10%–30% compared to the results of another wavelet algorithm; (2) the new algorithm was stable under different circumstances. Besides, an actual reconstruction experiment was performed using real projection data that had been collected in a CT experiment. Two-dimensional (2D) and three-dimensional (3D) images of the sample were reconstructed. The microstructure of the sample could be clearly observed in the reconstructed images. Since much attention has been directed towards the nano-CT technique to investigate the microstructure of materials, this new wavelet-based local tomography algorithm could be considered as a meaningful effort.

Free collisions in a microgravity many-particle experiment. III. The collision behavior of sub-millimeter-sized dust aggregates

We conducted micro-gravity experiments to study the outcome of collisions between sub-mm-sized dust agglomerates consisting of μm-sized SiO2 monomer grains at velocities of several cms−1. Prior to the experiments, we used X-ray computer tomography (nano-CT) imaging to study the internal structure of these dust agglomerates and found no rim compaction so that their collision behavior is not governed by preparation-caused artefacts. We found that collisions between these dust aggregates can lead either to sticking or to bouncing, depending mostly on the impact velocity. While previous collision models derived the transition between both regimes from contact physics, we used the available empirical data from these and earlier experiments to derive a power law relation between dust-aggregate mass and impact velocity for the threshold between the two collision outcomes. In agreement with earlier experiments, we show that the transition between both regimes is not sharp, but follows a shallower power law than predicted by previous models (Güttler, C., Blum, J., Zsom, A., Ormel, C.W., Dullemond, C.P. [2010]. Astron. Astrophys. 513, A56). Furthermore, we find that sticking between dust aggregates can lead to the formation of larger structures. Collisions between aggregates-of-aggregates can lead to growth at higher velocities than homogeneous dust agglomerates.

A Numerical Study on the Heat Generation in LiCoO2 Cathode Electrode by Using X-ray Nano-CT Images

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Research progress of Nano CT imaging

Nano CT is a new kind of imaging device which is derived from Micro-CT but with higher resolution. At present, it has been wildly used in many fields such as biology imaging, pathological examination, integrated circuit testing and so on, and it is believed to have broad application prospects. This paper focuses on the development, the basic principles, the key technologies, all kinds of imaging problems of Nano CT and some limitations in imaging such as motion imaging and multiresolution imaging. In the last part of this paper, several new technologies are introduced which may be applied in prospective more advanced Nano CT to eliminate the limitations in the imaging. These new techniques may greatly help improving the Nano CT in the future.

Three Dimensional Simulation of Galvanostatic Discharge of LiCoO2 Cathode Based on X-ray Nano-CT Images

Based on the experimentally determined microstructure of a lithium ion battery (LIB) cathode electrode using X-ray nano-CT technology, a three dimensional simulation framework of galvanostatic discharge with finite volume method is presented. The tomography data were used to evaluate the homogeneity of porosity and tortuosity of the electrode. With this approach, galvanostatic discharge processes at different C rates were simulated and the local effects in the LIB cathode electrode during discharge processes were investigated. The spatial distribution of physical and electrochemical properties in the microsturcture of the cathode electrode, such as concentration, current density, open circuit potential (OCP), overpotential and intercalation reaction rate was revealed in this paper. The simulation results show that the distributions of those properties are very different from the results based on the pseudo two dimensional model. The physical and electrochemical properties distribute in a wider range due to the structure inhomogeneity, which may have a negative impact on LIB performance, especially at large discharge rates.

Quantitative analysis of micro structural and conductivity evolution of Ni-YSZ anodes during thermal cycling based on nano-computed tomography

Understanding the mechanism of degradation in solid oxide fuel cells (SOFCs) using nickel/yttria-stabilized zirconia (Ni-YSZ) as the anode material is very important for the optimization of cell performance. In this work, the effects of thermal cycling on the microstructure of the Ni-YSZ anode are explored using the three-dimensional X-ray nano computed tomography (nano-CT) imaging technique. It is found that the average Ni particle size increased with thermal cycling, which is associated with the decreased connectivity of the Ni phase and the three-phase-boundary (TPB) length. Moreover, the conductivities of the anode samples are also reduced with the increase in thermal cycle times. The implication of these observations is discussed in terms of the relationship between the conductivity and connectivity of the Ni phase.

Assessment of angiogenesis in osseointegration of a silica–collagen biomaterial using 3D-nano-CT

Bony integration of biomaterials is a complex process in which angiogenesis plays a crucial role. We evaluated micro- and nano-CT imaging to demonstrate and quantify neovascularization in bony integration of a biomaterial and to give an image based estimation for the needed resolution for imaging angiogenesis in an animal model of femora defect healing. In 8 rats 5 mm full-size defects were created at the left femur that was filled with silica-collagen bone substitute material and internally fixed with plate osteosynthesis. After 6 weeks the femora were infused in situ with Microfil, harvested and scanned for micro-CT (9 μm) 3 and nano-CT (3 μm) 3 imaging. Using those 3D images, the newly formed blood vessels in the area of the biomaterial were assessed and the total vascular volume fraction, the volume of the bone substitute material and the volume of the bone defect were quantitatively characterized. Results were complemented by histology. Differences were statistically assessed using (ANOVA). High-resolution nano-CT demonstrated new blood vessel formation surrounding the biomaterial in all animals at capillary level. Immunohistochemistry confirmed the newly formed blood vessels surrounding the bone substitute material. The mean vascular volume fraction (VVF) around the implant was calculated to be 3.01 ± 0.4%. The VVF was inversely correlated with the volume of the bone substitute material ( r = 0.8) but not with the dimension of the fracture zone ( r = 0.3). Nano-CT imaging is feasible for quantitative analysis of angiogenesis during bony integration of biomaterials and a promising tool in this context for the future.

3-Dimensional Structural and Volumetric Analysis of Glomeruli in Porcine Kidneys with Renal Artery Stenosis using Nano-Computed Tomography

Ziele: Renovascular disease is one of the most important causes of hypertension and renal dysfunction, and may lead to renal microvascular remodeling. Therefore, renal microvascular alterations were obtained in pigs after ten weeks of unilateral renal artery stenosis (RAS) using nano-CT imaging. Methode: Seven female domestic pigs (45–55kg) were implanted through PTCA with local-irritant coils in the left renal artery, provoking formation of a unilateral RAS and thus a systemic renovascular hypertension. Blood pressure was recorded using a telemetry system. The degree of RAS was determined in vivo by renal angiography. After ten weeks, the animals were sacrificed. The contralateral kidneys were infused post mortem with contrast agent (Microfil®) and fixed in formalin. Kidneys of eight healthy female pigs (45–55kg) served as controls. The number of glomeruli, glomerular capillary volume, as well as the total vascular volume fraction were quantified and measured in nano-CT scans at 0.75µm, 2.0µm and 2.5µm. All results from nano-CT were complemented with co-localized histology. Ergebnis: Number of glomeruli per unit of area (mm2), as well as the glomerular capillary volume (µm3) was significantly higher in control compared to RAS animals (number of glomeruli per unit area 3.275±1.855 vs. 1.900±1.035, glomerular capillary volume 535 000±296 000µm3 vs. 223 000±111 000µm3, p<0.0001). The total vascular volume fraction per unit of volume (µm3) was significantly higher in control animals as compared to pigs with RAS (0.073±0.039 vs. 0.035±0.011, p=0.03). Schlussfolgerung: Using nano-CT, we observed a significant decrease of the total vascular volume fraction, glomerular capillary volume, and the number of glomeruli in pigs with RAS compared to healthy control animals. Nano-CT imaging is a promising new method for fast acquisition of quantitative and qualitative experimental information about parenchymal alterations in kidneys with RAS.

Quantification of the 3-Dimensional Glomeruli Capillary System in Adult Pigs using Micro- and Nano-CT Imaging

Ziele: To evaluate the feasibility for analysis of the kidney glomeruli capillary unit in adult pics using micro- and nano-CT imaging. Methode: Kidneys were harvested from five healthy hybrid pics (6 mo of age; weight 120kg) at a local slaughterhouse and infused with a mixture of BaSO4 and gelatine. Kidney samples (6-mm diameter, 10mm height, n=20) were punched out, harvested and scanned with micro-CT (12µm cubic voxels) and nano-CT (450nm cubic voxels). Diameter and cross-sectional area (µm2) of glomeruli were measured using micro-CT, nano-CT and histology. Moreover, the capillary vessel volume (mm3) within single glomeruli was quantitated using nano-CT. Ergebnis: The glomeruli diameter and cross-sectional area increased significantly as measured by histology, nano-CT and micro-CT (231±30µm, 0.03392 ±0.0091µm2; 252±28µm, 0.04148±0.009µm2; 269±37µm, 0.04763 ±0.01µm2, p<0.001; respectively). Quantitative nano-CT analysis demonstrated a strong linear relationship of the volume of glomeruli and the capillary volume (r2=0.97). Schlussfolgerung: These results demonstrate potential use of quantitative 3D micro- and nano-CT imaging to obtain information about glomeruli dimensions' and vascularisation, which could be useful in animal models of kidney alterations.

Angioarchitectural Changes in Acute and Chronic Cerebral Venous Thrombosis. A Synchrotron-based Micro- and Nano-CT Study

Aim: It is well known that recanalization of thrombosed cerebral sinuses occurs early but without marked influence on the long-term outcome. To better understand the mechanisms behind these clinical observations, we evaluated the sequels of chronic superior sagittal sinus (SSS) thrombosis in rats using micro- and nano-CT imaging.

Angioarchitectural changes in subacute cerebral venous thrombosis. A synchrotron-based micro- and nano-CT study

It is well known that recanalization of thrombosed cerebral sinuses occurs early but without marked influence on the long-term outcome and on final venous infarct volume on magnetic resonance imaging. To better understand the possible microvascular mechanisms behind these clinical observations, we evaluated the sequels of subacute superior sagittal sinus (SSS) thrombosis in rats using micro- and nano-CT imaging of the same specimen to provide large volume and high resolution CT image data respectively.SSS thrombosis was induced in 11 animals which were euthanized after 6h (n=4) or 6weeks (n=7). Eight sham-operated rats served as controls. After infusion of contrast into the vasculature of the brains, these were isolated and scanned using micro-, nano-, and synchrotron-based micro-CT ((8μm³), (900nm)³, and (1.9μm³) voxel sizes). The cross-sectional area of the superior sagittal sinus, microvessels and cortical veins were quantified. Tissue sections were stained against VEGF antigen. Immunohistochemistry was confirmed using quantitative rtPCR.SSS thrombosis led to a congestion of the bridging veins after 6h. After 6weeks, a network of small vessels surrounding the occluded SSS was present with concurrent return towards the diameter of the draining bridging veins of controls. This microvascular network connected to cortical veins as demonstrated by nano- and synchrotron-based micro-CT. Also the volume fraction and number of cortical veins increased significantly. Immunohistochemistry in the region of the microsvascular network demonstrated a strong immunoreactivity against VEGF, confirmed by rtPCR.The sequel of subacute SSS thrombosis induced a network of microvessels (“venogenesis”) draining the bridging veins. Also the volume fraction of cortical veins increased significantly.

Evaluation of the middle cerebral artery occlusion techniques in the rat by in-vitro 3-dimensional micro- and nano computed tomography

BackgroundAnimal models of focal cerebral ischemia are widely used in stroke research. The purpose of our study was to evaluate and compare the cerebral macro- and microvascular architecture of rats in two different models of permanent middle cerebral artery occlusion using an innovative quantitative micro- and nano-CT imaging technique.Methods4h of middle cerebral artery occlusion was performed in rats using the macrosphere method or the suture technique. After contrast perfusion, brains were isolated and scanned en-bloc using micro-CT (8 μm)3 or nano-CT at 500 nm3 voxel size to generate 3D images of the cerebral vasculature. The arterial vascular volume fraction and gray scale attenuation was determined and the significance of differences in measurements was tested with analysis of variance [ANOVA].ResultsMicro-CT provided quantitative information on vascular morphology. Micro- and nano-CT proved to visualize and differentiate vascular occlusion territories performed in both models of cerebral ischemia. The suture technique leads to a remarkable decrease in the intravascular volume fraction of the middle cerebral artery perfusion territory. Blocking the medial cerebral artery with macrospheres, the vascular volume fraction of the involved hemisphere decreased significantly (p < 0.001), independently of the number of macrospheres, and was comparable to the suture method. We established gray scale measurements by which focal cerebral ischemia could be radiographically categorized (p < 0.001). Nano-CT imaging demonstrates collateral perfusion related to different occluded vessel territories after macrosphere perfusion.ConclusionMicro- and Nano-CT imaging is feasible for analysis and differentiation of different models of focal cerebral ischemia in rats.

In vitro evaluation of the sinus sagittalis superior thrombosis model in the rat using 3D micro- and nanocomputed tomography

Thrombosis of the cerebral veins and sinus are common causes of stroke. Animal models help us to understand the underlying pathophysiology of this condition. Therefore, the purpose of our study was to evaluate a well-established model for sinus sagittalis (SSS) thrombosis using micro- and nanocomputed tomography (CT) imaging. SSS thrombosis was performed in four rats. After contrast perfusion, brains were isolated and scanned using micro-CT at (8 microm)(3) voxel size to generate 3D images of the cerebral vasculature. For more detailed information on vascular perfusion territories, nano-CT imaging was performed to investigate the boundary layer of contrast-enhanced vessels and the occluded veins. The venous and arterial vascular volume fraction and gray scale measurements were obtained in the SSS thrombosis group and compared to controls. The significance of differences in vascular volume fraction and gray scale measurements was tested with analysis of variance. Results were complemented with histology. Micro-CT proved to accurately visualize and differentiate vascular occlusion territories performed in the SSS thrombosis model. Moreover, 3D micro-CT provided quantitative information on arterial and venous vascular volume fraction. Micro-CT imaging enables a total 3D visualization of complications (ventricle rupture) in the SSS thrombosis model. We established gray scale measurements by which focal cerebral ischemia could be radiographically categorized (p < 0.001). Using nano-CT, the interface of contrast-perfused and occluded veins can be visualized. Micro-CT is feasible for analysis and differentiation of perfusion territories in an animal model of focal cerebral ischemia.