SR micro-CT Research Articles

Quantification of cartilage and subchondral bone cysts on knee specimens based on a spectral photon-counting computed tomography

Spectral photon-counting computed tomography (SPCCT) is a new technique with the capability to provide mono-energetic (monoE) images with high signal to noise ratio. We demonstrate the feasibility of SPCCT to characterize at the same time cartilage and subchondral bone cysts (SBCs) without contrast agent in osteoarthritis (OA). To achieve this goal, 10 human knee specimens (6 normal and 4 with OA) were imaged with a clinical prototype SPCCT. The monoE images at 60 keV with isotropic voxels of 250 × 250 × 250 µm3 were compared with monoE synchrotron radiation CT (SR micro-CT) images at 55 keV with isotropic voxels of 45 × 45 × 45 µm3 used as benchmark for cartilage segmentation. In the two OA knees with SBCs, the volume and density of SBCs were evaluated in SPCCT images. In 25 compartments (lateral tibial (LT), medial tibial, (MT), lateral femoral (LF), medial femoral and patella), the mean bias between SPCCT and SR micro-CT analyses were 101 ± 272 mm3 for cartilage volume and 0.33 mm ± 0.18 for mean cartilage thickness. Between normal and OA knees, mean cartilage thicknesses were found statistically different (0.005 < p < 0.04) for LT, MT and LF compartments. The 2 OA knees displayed different SBCs profiles in terms of volume, density, and distribution according to size and location. SPCCT with fast acquisitions is able to characterize cartilage morphology and SBCs. SPCCT can be used potentially as a new tool in clinical studies in OA.

Pore-scale dual-porosity and dual-permeability modeling in an exposed multi-facies porous carbonate reservoir

Fracture networks in porous carbonates can control, assist, or even contribute negatively to reservoir quality. In scenarios where fractures and matrix pore systems are of similar importance, a dual-porosity/permeability (DP/P) modeling approach is necessary or at least recommendable for the reservoir characterization. These workflows are well established at the reservoir scale, however at the microscale, the interaction between fractures and porous matrix needs to be further investigated.The aim of this work is to assess the contribution of meter-scale fractures (macrofractures) to the porosity and permeability in a porous carbonate reservoir analogue at the microscale. To reach this objective, we created DP/P models at the microscale through the integration of two different methods of 3D imaging such as, high-resolution synchrotron X-ray microtomography (SR micro-CT) and Structure from Motion (SfM) photogrammetry. Quantitative analyses of pristine rock and DP/P models were performed to evaluate the contribution of macrofracture segments to the porosity and connectivity of the pore network. These results were integrated with single-phase flow simulations for calculating permeability values. Different scenarios were modeled in order to systematically evaluate the control exerted by fracture roughness parameters (i.e., asperity height distribution and fractal dimension) on porosity and permeability in various lithofacies.The key analyzed samples come from the Roman Valley quarry located at the Majella Mountain (central Italy), which has been widely investigated due to the presence of consistent bitumen impregnations distributed in pervious medium-to-coarse grainstones and along two main fault zones. The results of this study demonstrate the utility of obtaining DP/P microscale models as complementary approach to explain the hydrocarbon distribution in fractured multi-facies porous carbonates. We document the potential of macrofracture segments to provide neo-connected porosity by linking up adjacent isolated or partially isolated matrix pore networks in impervious carbonate rocks. In pervious carbonate lithofacies, fault-related macrofractures can enhance permeability and contribute to bitumen migration and distribution, whereas the increment of storage capacity is limited since these rocks are already fully connected. In the case of impervious carbonate lithofacies, results indicate that the actual contribution of neo-connected pores to fluid transport is limited, which agrees with outcrop observations.

Quantitative pore network analysis and permeability evaluation of porous carbonate reservoir rocks using X-ray computed microtomography images

The texture and the morphology of the pore network exerts a primary control in the fluid storage and migration of geofluids within porous carbonates reservoirs. The architecture of the pore network of porous carbonates are highly variable because of primary depositional settings, diagenesis processes and deformation. This issue represents an important challenge for the characterization and exploitation plan of this type of reservoirs in different industries such as, hydrocarbon, ground water and geothermal energy. This type of rocks is widely studied because they represent important reservoirs for geofluids around the globe. However, there are few studies assessing the control exerted by the pore network properties (e.g. porosity, pore size distribution, connectivity, tortuosity) on the permeability. In this work the control exerted by the pore network on the storage and migration capacity in porous carbonates is evaluated by combining synchrotron X-ray computed microtomography (SR micro-CT) and computational fluid dynamics. The studied rock samples are mainly porous grainstones exposed in south and central Italy. Some samples may content deformation structures (i.e. deformation bands) or may be altered by diagenesis. Previous studies have reported permeability differences and significant variability of the in-situ hydrocarbon distribution in the studied rocks. The SR micro-CT imaging experiments were performed at the SYRMEP (SYnchrotron Radiation for MEdical Physics) beamline (Elettra-Sincrotrone Trieste laboratory, Italy). This beamline was suitable for studying the rocks samples due to its nearly-parallel geometry and a high spatial coherence allowing the phase contrast effects to enhance the visibility of objects with similar linear attenuation coefficients. In this study, the selected spatial resolution of the images is variable (1.0-9.0 μm) depending on the grain size distribution of the rock sample. The SR micro-CT images were used for both performing a quantitative pore network analysis of the studied rock samples and performing computational fluid dynamics experiments. These experiments consist in simulating a pressure-driven flow by using the lattice-Boltzmann method (LBM) with multiple relaxation time (MRT) approach. This method generates viscosity-independent results of permeability. The permeability of the volume was calculated using Darcy’s law once steady conditions were reached. To evaluate isotropy, the results of permeability and the pore network properties were calculated in three dimensions. The results indicate that deformation and diagenetic processes may have and important impact on the pore network properties and therefore on storage (porosity) and migration (permeability) capacity of the studied rocks.

Fluid flow simulation and permeability computation in deformed porous carbonate grainstones

Abstract In deformed porous carbonates, the architecture of the pore network may be modified by deformation or diagenetic processes altering the permeability with respect to the pristine rock. The effects of the pore texture and morphology on permeability in porous rocks have been widely investigated due to the importance during the evaluation of geofluid reservoirs. In this study, these effects are assessed by combining synchrotron X-ray computed microtomography (SR micro-CT) and computational fluid dynamics. The studied samples pertain to deformed porous carbonate grainstones highly affected by deformation bands (DBs) exposed in Northwestern Sicily and Abruzzo regions, Italy. The high-resolution SR micro-CT images of the samples, acquired at the SYRMEP beamline of the Elettra - Sincrotrone Trieste laboratory (Italy), were used for simulating a pressure-driven flow by using the lattice-Boltzmann method (LBM). For the experiments, a multiple relaxation time (MRT) model with the D3Q19 scheme was used to avoid viscosity-dependent results of permeability. The permeability was calculated using Darcy's law once steady conditions were reached. After the simulations, the pore-network properties (effective porosity, specific surface area, and geometrical tortuosity) were calculated using 3D images of the velocity fields. These images were segmented considering a velocity threshold value higher than zero. The study showed that DBs may generate significant heterogeneity and anisotropy of the permeability of the evaluated rock samples. Cataclasis and cementation process taking place within the DBs reduce the effective porosity and therefore the permeability. Contrary to this, pressure dissolution and faulting may generate connected channels which contribute to the permeability only parallel to the DB.

Occurrence of osteon banding in adult human cortical bone.

Differentiating human from nonhuman fragmented bone is often accomplished using histological methods if the observation of gross morphology proves insufficient. Linearly oriented primary and/or secondary osteonal systems, commonly referred to as osteon bands, are described as a strong indicator of nonhuman bone, particularly the occurrence of multiple bands. This phenomenon has been conventionally documented using two-dimensional (2D) histology, but such analyses are destructive and typically limited to a single cross-section. Progressive developments in high-resolution X-ray imaging, however, allow for the nondestructive three-dimensional (3D) visualization of bone microarchitecture. The primary objective of the current research was to visualize and document the occurrence of osteon banding in adult human cortical bone using high-resolution synchrotron radiation-based micro-Computed Tomography (SR micro-CT). Synchrotron radiation-based micro-CT scanning was carried out at the Canadian Light Source (CLS) national synchrotron facility. The presence or absence of osteon banding was visualized in human skeletal elements from three adult males with representative samples from all regions of the skeleton (n = 129). If present, osteon banding was described and quantified. Results indicated that 23 of 129 human cortical bone specimens exhibited osteon banding, representing 18% of the sample. Linear arrangements of primary and/or secondary osteons were observed in the following skeletal elements: temporal, parietal, frontal, occipital, clavicle, mandible, femur, tibia, ulna, second metatarsal, and sacrum. The present work represents the first 3D examination of inter-element variation in osteon banding in adult human cortical bone. Findings indicate that the presence of multiple osteon bands in a single specimen is not diagnostic of nonhuman bone. As such, osteon banding categorically should not be taken as evidence of nonhuman bone in forensic and archaeological contexts.

Synchrotron radiation μCT and histology evaluation of bone-to-implant contact

The purpose of this study was to evaluate bone-to-implant contact (BIC) in two-dimensional (2D) histology compared to high-resolution three-dimensional (3D) synchrotron radiation micro computed tomography (SR micro-CT). High spatial resolution, excellent signal-to-noise ratio, and contrast establish SR micro-CT as the leading imaging modality for hard X-ray microtomography. Using SR micro-CT at voxel size 5 μm in an experimental goat mandible model, no statistically significant difference was found between the different treatment modalities nor between recipient and reconstructed bone. The histological evaluation showed a statistically significant difference between BIC in reconstructed and recipient bone (p < 0.0001). Further, no statistically significant difference was found between the different treatment modalities which we found was due to large variation and subsequently due to low power. Comparing histology and SR micro-CT evaluation a bias of 5.2% was found in reconstructed area, and 15.3% in recipient bone. We conclude that for evaluation of BIC with histology and SR micro-CT, SR micro-CT cannot be proven more precise than histology for evaluation of BIC, however, with this SR micro-CT method, one histologic bone section is comparable to the 3D evaluation. Further, the two methods complement each other with knowledge on BIC in 2D and 3D.

Evaluating differential nuclear DNA yield rates and osteocyte numbers among human bone tissue types: A synchrotron radiation micro-CT approach

Molecular human identification has conventionally focused on DNA sampling from dense, weight-bearing cortical bone tissue, typically from femora or tibiae. A comparison of skeletal elements from three contemporary individuals demonstrated that elements with high quantities of cancellous bone yielded nuclear DNA at the highest rates, suggesting that preferentially sampling cortical bone may be suboptimal (Mundorff & Davoren, 2014). Despite these findings, the reason for the differential DNA yields between cortical and cancellous bone tissues remains unknown. The primary goal of this work is to ascertain whether differences in bone microstructure can be used to explain differential nuclear DNA yield among bone tissue types observed by Mundorff and Davoren (2014), with a focus on osteocytes and the three-dimensional (3D) quantification of their associated lacunae. Osteocytes and other bone cells are recognized to house DNA in bone tissue, thus examining the density of their lacunae may explain why nuclear DNA yield rates differ among bone tissue types. Lacunae were visualized and quantified using synchrotron radiation-based micro-Computed Tomographic imaging (SR micro-CT). Volumes of interest (VOIs) from cortical and cancellous bone tissues (n=129) were comparatively analyzed from the three skeletons sampled for Mundorff and Davoren’s (2014) study. Analyses tested the primary hypothesis that the abundance and density of osteocytes (inferred from their lacunar spaces) vary between cortical and cancellous bone tissue types. Results demonstrated that osteocyte lacunar abundance and density vary between cortical and cancellous bone tissue types, with cortical bone VOIs containing a higher lacunar abundance and density. We found that the osteocyte lacunar density values are independent of nuclear DNA yield, suggesting an alternative explanation for the higher nuclear DNA yields from bones with greater quantities of cancellous bone tissue. The use of SR micro-CT allowed for a scale of analysis that revealed a high range of variation in lacunar abundance in both tissue types. Moreover, high-resolution SR micro-CT imaging revealed potential soft tissue remnants within marrow spaces not visible macroscopically. It is hypothesized that soft tissue remnants observed among the trabeculae of skeletal elements with high quantities of cancellous bone tissue are responsible for the high nuclear DNA yields. These findings have significant implications for bone-sample selection for nuclear DNA analysis in a forensic context when skeletal remains are recovered from the ground surface.

QUANTIFICATION OF THE 3D MORPHOLOGY OF THE BONE CELL NETWORK FROM SYNCHROTRON MICRO-CT IMAGES

In the context of bone diseases research, recent works have highlighted the crucial role of the osteocyte system. This system, hosted in the lacuno-canalicular network (LCN), plays a key role in the bone remodeling process. However, few data are available on the LCN due to the limitations of current microscopy techniques, and have mainly only been obtained from 2D histology sections. Here we present, for the first time, an automatic method to quantify the LCN in 3D from synchrotron radiation micro-tomography images. After segmentation of the LCN, two binary images are generated, one of lacunae (hosting the cell body) and one of canaliculi (small channels linking the lacunae). The binary image of lacunae is labeled, and for each object, lacunar descriptors are extracted after calculating the second order moments and the intrinsic volumes. Furthermore, we propose a specific method to quantify the ramification of canaliculi around each lacuna. To this aim, a signature of the numbers of canaliculi at different distances from the lacunar surface is estimated through the calculation of topological parameters. The proposed method was applied to the 3D SR micro-CT image of a human femoral mid-diaphysis bone sample. Statistical results are reported on 399 lacunae and their surrounding canaliculi.

English

Synchrotron radiation micro-computed tomography (SR micro-CT), considered superior to standard polychromatic micro-CT techniques, was used to assess the densities of bovine enamel white-spot lesions (WSL) treated in a 10-day pH cycling model with either: (A) Clinpro Tooth Cr&egrave;me (0.21% NaF plus TCP), (B) Clinpro 5000 (1.1% NaF plus TCP) or (C) Tom&rsquo;s of Maine (0% NaF) dentifrice. Each day consisted of four 2 min treatments, one 4 h acid challenge (pH=5.0), and immersion in artificial saliva (pH=7.0) between these events. After 10 days, WSL specimens were evaluated for lesion depth using confocal microscopy and lesion density using SR micro-CT with depths ranging from 2.76 to 113.16 &mu;m, in 2.76 &mu;m slice increments. Statistical analyses (Student&rsquo;s t-test) were performed at the 95% confidence level. SR micro-CT analyses revealed the NaF plus TCP dentifrices improved WSL densities relative to the fluoride-free toothpaste, and is consistent with an earlier study utilizing polychromatic micro-CT. In contrast to previous findings, SR micro-CT analyses also revealed significant differences in WSL densities treated with the two NaF dentifrices at enamel depths of 13.80, 16.56, and 19.32 &mu;m. These findings suggest SR micro-CT may be especially suited for detecting density differences in lesions sensitive to fluoride-driven remineralization processes. Key words: Toothpaste, synchrotron radiation micro computed tomography (SR micro-CT), density, remineralization, fluoride, monochromatized X-ray beams, X-ray linear attenuation coefficient (X-ray LAC).

P2-09-14: Evaluation of Angiogenesis Using Synchrotron Radiation in Xenograft Mouse Models of Breast Cancer.

Abstract Visualization of microvasculatures is an important step in understanding the mechanism of early vessel disorders in breast cancer and developing effective therapeutic strategies. However, quantitative evaluation of breast cancer angiogenesis using immunohistochemistry has been limited in generating detailed and reproducible data. To analyze the diversification of angiogenesis in the development of tumor growth and evaluate anti-vascular effects of Avastin, a new method of microvascular imaging was introduced in this paper. We used New X-ray microangiography and third-generation synchrotron radiation-based micro-computed tomography (SR micro-CT) to investigate the structures and density of microvessels at each stage of xenograft mouse models that were created by inoculation with MDA-MB-231HM cells (one breast cancer cell line with high metastasis potential). Barium Sulfate Nanoparticles, was used as a blood vessels contrast agent through left cardiac ventricle. Three dimensional structures of microvessels were displayed with a high spatial image resolution at around 20–30 μm. The density of microvessles was significantly reduced from the third week in mouse xenograft models. This observation with SR micro-CT was consistent with the results analyzed by immunohistochemical techniques. In addition, human breast cancer-bearing mice were treated site-specifically with humanized monoclonal antibody (Avastin) that targets all isoforms of VEGF-A. Tumor volume and the density of angiogenesis were significantly reduced in xenograft mouse models of breast cancer treated with avastin when compared with untreated mice as assessed by SR micro-CT. Specifically, the density of smaller vessels (di&amp;lt;50μm) was decreased significantly while the density of larger vessels was little changed in the Avastin-treated mice. Therefore, synchrotron radiation technique is a novel method for investigating breast cancer angiogenesis, and this might be considered as an additional complementary tool for more precise quantification of angiogenesis. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-09-14.

Three-Dimensional Visualization of Bioactive Glass-Bone Integration in a Rabbit Tibia Model Using Synchrotron X-Ray Microcomputed Tomography

Synchrotron X-ray microcomputed tomography (SR microCT), with a micron resolution, was used to evaluate the osteoconduction and osteointegration by borate bioactive glass after implantation 12 weeks in a rabbit tibia model. The study focused on the biomaterial-bone interface. Results from SR microCT two-dimensional and three-dimensional (3D) reconstructions provided precise imaging of the biomaterial-bone integration and detailed microarchitecture of both the bone-like glass graft and the newly formed trabecular bone. Osteoconduction, the formation of new trabecular bone within a tibia defect, occurred only in the tibiae implanted with teicoplanin-loaded borate glass but not in those with teicoplanin-loaded CaSO(4) beads, indicating the excellent biocompatibility of the glass implants. 3D reconstruction of the tibiae also showed the infiltration of vascular tissue in both the bioactive glass graft and the new trabecular bone. This study indicates that SR microCT can serve as a valuable complementary technique for imaging bone repair when using bioactive glass implants.

Observation of Fatigue Crack Propagation Behavior under Torsional Loading by Using Synchrotron Radiation Micro-CT Imaging

In the present study, synchrotron radiation micro computed tomography (SR CT) imaging of SPring-8 was applied to the observation of the torsion fatigue crack propagation behavior. The transition of crack propagation from Mode II to I occurs under torsion fatigue. The conventional technique, such as optical microscope and scanning microscope, cannot give us the crack growth behavior under the surface. Therefore, the transition of crack propagation could not be discussed in detail. The compact torsion fatigue-testing machine was developed for fatigue testing at SPring-8, and thetorsion fatigue tests and measurements of SR micro-CT were carried out alternately. The shape of torsion fatigue cracks could be evaluated quantitatively and nondestructively. Transition of crack propagation from Mode II to Mode I under the surface could be observed. The condition of transition of crack propagation was discussed by using three-dimensional shape of cracks.

Observation of crack propagation under torsion fatigue tests by synchrotron radiation [formula omitted] imaging

In the present study, synchrotron radiation micro computed tomography (SR μCT) imaging of SPring-8 was applied to the observation of the torsion fatigue crack propagation behavior. The transition of crack propagation from Mode II to I occurs under torsion fatigue. The conventional technique, such as optical microscope and scanning microscope, cannot give us the crack growth behavior under the surface. Therefore, the transition of crack propagation could not be discussed in detail. The compact torsion fatigue-testing machine was developed for fatigue testing at SPring-8, and the torsion fatigue tests and measurements of SR micro-CT were carried out alternately. The shape of torsion fatigue cracks could be evaluated quantitatively and nondestructively. Transition of crack propagation from Mode II to Mode I under the surface could be observed. The condition of transition of crack propagation was discussed by using three-dimensional shape of cracks.

In vivo imaging of bone micro-architecture in mice with 3D synchrotron radiation micro-tomography

Micro-tomographic imaging of bone micro-architecture is increasingly used on wild and transgenic mice to follow effects of diseases or therapeutics. Synchrotron radiation micro-tomography (SR micro-CT) provides quantitative images at very high spatial resolution but has mainly been used in vitro. The aim of this work was to show the feasibility of SR micro-CT for assessing bone mineral density and micro-architecture in vivo in mice. Imaging with a pixel size of 10 μm was performed on beam line ID19 at the ESRF using a special mouse holder. Two strains of mice (C3H/HeJ and C57BL/6J) were used for the experiment. First tests were performed in order to optimize the imaging conditions with respect to dose. Then, six mice of each group were imaged at doses of 7 and 13 Gy (total scan time <5 min). A similar volume of interest was selected in each image to perform quantitative analysis. The first results on bone volume and mineralization revealed significant differences between the strains as expected. Although there was no apparent damage, the imaged femurs will be further investigated by histology to evaluate the effect of irradiation on bone cells. In conclusion, SR micro-CT provides in vivo images with high signal-to-noise ratio (SNR), very short scan time and may be used in longitudinal studies.