Dependence of threshold variations on the assessment of histomorphometric indices from computed microtomography using synchrotron radiation

In this work, the variation of threshold level for segmentation of tomographic image in a micron scale accomplished with synchrotron radiation was studied. Three different sites of rat femora were evaluated from computed microtomography performed at SYRMEP beamline of ELETTRA Synchrotron Laboratory with a resolution of 9 μm. An optimal threshold level was selected and then varied in two points up and down in steps of one point, corresponding to 0.39% per point. Histomorphometric indices were calculated directly from the three dimensional segmented images of trabecular microstructure. The results showed that histomorphometric indices presented small variations for all indices in all femur sites. The greater variation occurred for trabecular thickness (Tb.Th) [from ?2.84% to 2.99%] while the smaller one occurred for trabecular number (Tb.N) [?0.26% to 0.35].     

X射线显微CT用于大鼠骨小梁结构分析的研究

应用X射线显微CT(X-μCT)对正常及骨质疏松大鼠的骨小梁结构进行了分析,并与骨组织形态计量法的测量值进行了比较,探讨了X射线光谱技术在骨结构分析中的应用。实验对大鼠骨样品进行X-μCT扫描,扫描条件为 80 kVp,80 μA,360°旋转,帧平均4帧,角度增益 0.4°,分辨率14 μm。三维重建并分析了骨小梁结构,结构参数包括骨体积分数(BV/TV)、骨小梁厚度(Tb.Th)、骨小梁数量(Tb.N)以及骨小梁间隔(Tb.Sp)。结果表明,采用X-μCT分析不同组大鼠的骨小梁结构参数值之间存在显著差异(P<0.05),测定值与传统骨组织形态计量法的测定值显著相关,其中胫骨骨小梁BV/TV,Tb.Th,Tb.N,Tb.Sp的相关系数r分别为0.984,0.960,0.995,0.988,腰椎骨小梁各结构参数的相关系数分别为0.938,0.968,0.877,0.951。因此,X-μCT可以较好地呈现并区分正常骨组织、骨质疏松骨组织以及经雌激素治疗后骨组织的微观结构,可以实现对骨小梁结构参数的分析测定,与骨组织形态计量法相比是一种更精确、立体、快速且无损测量骨微结构和评价骨质量的方法。     

Effects of risedronate in a rat model of osteopenia due to orchidectomy and disuse: densitometric, histomorphometric and microtomographic studies

Dual energy X-ray absorptiometry (DXA), histomorphometry and X-ray microtomography (microCT) were used to assess effects of risedronate and testosterone in a combined rat model of orchidectomy (ORX) and local paralysis induced by botulinum neurotoxin (BTX). Four groups of mature rats were studied for 1 month: SHAM operated; ORX and right hindlimb immobilization (BTX); ORX+BTX+risedronate or testosterone. Changes in bone and body composition were measured by DXA (BMC, lean and fat mass), histomorphometry (BV/TV(2D), Tb.Th and microarchitectural parameters) and microCT (BV/TV(3D), SMI and cortical parameters). ORX and BTX had additive effects on bone loss since differences were maximized on the immobilized bone. The decrease in BMC on the tibial metaphysis reached -33.6% vs. -11.3% in the non-immobilized limb. BV/TV and Tb.N decreased and Tb.Sp increased in both hindlimbs whereas Tb.Th was significantly lower only in the immobilized limb. Decrease of tibial cortical area and thickness was greater in the immobilized limb. Risedronate prevented BMC, BV/TV and architecture loss but not reduction in Tb.Th. Cortical bone was preserved only in the non-immobilized limb. Testosterone was unable to prevent trabecular and cortical bone loss, but it prevents loss of whole body lean mass. In conclusion, ORX and BTX resulted in additive effects on bone loss. Risedronate had protective effects on trabecular bone loss but was less effective on cortical bone.     

Reproducibility of the quantitative assessment of cartilage morphology and trabecular bone structure with magnetic resonance imaging at 7 T

To assess the reproducibility of quantitative measurements of cartilage morphology and trabecular bone structure of the knee at 7 T, high-resolution sagittal spoiled gradient-echo images and high-resolution axial fully refocused steady-state free-precession (SSFP) images from six healthy volunteers were acquired with a 7-T scanner. The subjects were repositioned between repeated scans to test the reproducibility of the measurements. The reproducibility of each measurement was evaluated using the coefficient(s) of variation (CV). The computed CV were 1.13% and 1.55% for cartilage thickness and cartilage volume, respectively, and were 2.86%, 1.07%, 2.27% and 3.30% for apparent bone volume over total volume fraction (app.BV/TV), apparent trabecular number (app.Tb.N), apparent trabecular separation (app.Tb.Sp) and apparent trabecular thickness (app.Tb.Th), respectively. The results demonstrate that quantitative assessment of cartilage morphology and trabecular bone structure is reproducible at 7 T and motivates future musculoskeletal applications seeking the high-field strength's superior signal-to-noise ratio.     

Numerical simulation of wave propagation in cancellous bone

Numerical simulation of wave propagation is performed through 31 3D volumes of trabecular bone. These volumes were reconstructed from high synchrotron microtomography experiments and are used as the input geometry in a simulation software developed in our laboratory. The simulation algorithm accounts for propagation into both the saturating fluid and bone but absorption is not taken into account. We show that 3D simulation predicts phenomena observed experimentally in trabecular bones : linear frequency dependence of attenuation, increase of attenuation and speed of sound with the bone volume fraction, negative phase velocity dispersion in most of the specimens, propagation of fast and slow wave depending on the orientation of the trabecular network compared to the direction of propagation of the ultrasound. Moreover, the predicted attenuation is in very close agreement with the experimental one measured on the same specimens. Coupling numerical simulation with real bone architecture therefore provides a powerful tool to investigate the physics of ultrasound propagation in trabecular structures.     

Accuracy evaluation of an X-ray microtomography system

Microstructural parameter evaluation of reservoir rocks is of great importance to petroleum production companies. In this connection, X-ray computed microtomography (μ-CT) has proven to be a quite useful method for the assessment of rocks, as it provides important microstructural parameters, such as porosity, permeability, pore size distribution and porous phase of the sample. X-ray computed microtomography is a non-destructive technique that enables the reuse of samples already measured and also yields 2-D cross-sectional images of the sample as well as volume rendering. This technique offers an additional advantage, as it does not require sample preparation, of reducing the measurement time, which is approximately one to three hours, depending on the spatial resolution used. Although this technique is extensively used, accuracy verification of measurements is hard to obtain because the existing calibrated samples (phantoms) have large volumes and are assessed in medical CT scanners with millimeter spatial resolution. Accordingly, this study aims to determine the accuracy of an X-ray computed microtomography system using a Skyscan 1172 X-ray microtomograph. To accomplish this investigation, it was used a nylon thread set with known appropriate diameter inserted into a glass tube. The results for porosity size and phase distribution by X-ray microtomography were very close to the geometrically calculated values. The geometrically calculated porosity and the porosity determined by the methodology using the μ-CT was 33.4 ± 3.4% and 31.0 ± 0.3%, respectively. The outcome of this investigation was excellent. It was also observed a small variability in the results along all 401 sections of the analyzed image. Minimum and maximum porosity values between the cross sections were 30.9% and 31.1%, respectively. A 3-D image representing the actual structure of the sample was also rendered from the 2-D images.     

Assessment of 3D inhomogeneous microstructure of highly alloyed aluminium foam via dual energy K-edge subtraction imaging

X-ray microtomography was used to evaluate the inhomogeneous characteristics of newly-developed Al–Zn–Mg foam. Using the synchrotron K-edge subtraction technique, a highly heterogeneous distribution of Zn was quantified three-dimensionally (3D) in the cell wall of as-cast foam. Time-resolved analysis of the concentration evolution revealed a tendency to a homogeneous Zn distribution as solution time prolonged. This was accompanied by a declined variation in hardness measurement. Other microstructural features after solution treatment, such as number and size distribution of micropores, were also characterised. By utilising various quenching rates, the inhomogeneities in microstructure and compression properties inside the foam were also clarified. Thus, element-sensitive tomography provides a novel solution for the 3D/4D analysis in the study of foams.     

Study of the Biocatalyst Granule Distribution of Yeast Cells for a Continuous Bioreactor using the 3D X-Ray Tomography Technique

The methodology of studying the distribution of yeast cells in granules by 3D X-ray microtomography is presented. A method of cell dyeing by iodine-dodecanol solution is proposed. Granules with yeast biomass are investigated at the XRT-MT station of the Kurchatov source of synchrotron radiation. The distribution of the biomass over the granules is found. This method can be applied for other research in the field of biomass immobilization on different carrier materials used in the biotechnological industry.     

Multimode X-ray tomography at the mediana Station of the Kurchatov synchrotron radiation source

The synchrotron radiation used in X-ray tomography enables us to vary the recording conditions within wide limits due to the continuous spectrum and the beam’s high brightness and collimation. The possibilities of multimode X-ray tomography at the Mediana station of the Kurchatov synchrotron radiation source, including tomography and microtomography based on white and “pink” beams, imaging with the help of a monochromatic beam, and measurements via axial and refractive phase-contrast methods, are described. The presented results of the reconstruction of different objects have been obtained under different recording conditions.     

同步辐射X射线相衬显微CT在古生物学中的应用

X射线无损成像技术在古生物化石标本研究领域中应用十分广泛.近几年来,随着技术的不断革新,同步辐射X射线相衬显微断层成像技术(SRX-PC-μCT)也被引入到这一领域.由于同步辐射光源产生的硬X射线具有高亮度、高准直性和高空间相干性等优点,可以实现化石标本高分辨率（亚微米级）的无损三维显微成像,给古生物学的发展带来了新的机遇.文章简要回顾了用于古生物化石标本无损成像技术的发展历程,并在此基础上综述了同步辐射X射线断层显微成像技术在古生物学领域的应用现状和前景.     

Ultrasonically determined thickness of long cortical bones: Three-dimensional simulations of in vitro experiments

It was reported in a previous study that simulated guided wave axial transmission velocities on two-dimensional (2D) numerically reproduced geometry of long bones predicted moderately real in vitro ultrasound data on the same bone samples. It was also shown that fitting of ultrasound velocity with simple analytical model yielded a precise estimate (UTh) for true cortical bone thickness. This current study expands the 2D bone model into three dimensions (3D). To this end, wave velocities and UTh were determined from experiments and from time-domain finite-difference simulations of wave propagation, both performed on a collection of 10 human radii (29 measurement sites). A 3D numerical bone model was developed with tuneable fixed material properties and individualized geometry based on X-ray computed tomography reconstructions of real bones. Simulated UTh data were in good accordance (root-mean-square error was 0.40 mm; r(2)=0.79, p<0.001) with true cortical thickness, and hence the measured phase velocity can be well estimated by using a simple analytical inversion model also in 3D. Prediction of in vitro data was improved significantly (by 10% units) and the upgraded bone model thus explained most of the variability (up to 95% when sites were carefully matched) observed in in vitro ultrasound data.     

Applications of X-ray synchrotron microtomography for non-destructive 3D studies of paleontological specimens

Paleontologists are quite recent newcomers among the users of X-ray synchrotron imaging techniques at the European Synchrotron Radiation Facility (ESRF). Studies of the external morphological characteristics of a fossil organism are not sufficient to extract all the information for a paleontological study. Nowadays observations of internal structures become increasingly important, but these observations should be non-destructive in order to preserve the important specimens. Conventional microtomography allows performing part of these investigations. Nevertheless, the best microtomographic images are obtained using third-generation synchrotrons producing hard X-rays, such as the ESRF. Firstly, monochromatisation avoids beam hardening that is frequently strong for paleontological samples. Secondly, the high beam intensity available at synchrotron radiation sources allows rapid data acquisition at very high spatial resolutions, resulting in precise mapping of the internal structures of the sample. Thirdly, high coherence leads to additional imaging possibilities: phase contrast radiography, phase contrast microtomography and holotomography. These methods greatly improve the image contrast and therefore allow studying fossils that cannot be investigated by conventional microtomography due to a high degree of mineralisation or low absorption contrast. Thanks to these different properties and imaging techniques, a synchrotron radiation source and the ESRF in particular appears as an almost ideal investigation tool for paleontology. PACS 01.30.Cc; 07.05.Hd; 68.37.Yz; 29.20.Lq; 81.70.Tx     

同步辐射计算机断层技术光源误差机理分析

基于同步辐射X射线的优越特性及计算机断层重建技术对材料无损检测等优点,同步辐射计算机断层重建技术被广泛应用于很多领域.本文对光源非均匀、过饱和以及过穿透的三种情形所引起同步辐射计算机断层技术重建误差的形成机理进行了分析研究,给出了三种情形所引起误差的基本形式.在此基础上,对这三种误差进行了数值模拟,模拟结果证实了分析的正确性. 关键词： 同步辐射 计算机断层 光源 误差     

The 3D characteristics of post‐traumatic syringomyelia in a rat model: a propagation‐based synchrotron radiation microtomography study

Many published literature sources have described the histopathological characteristics of post‐traumatic syringomyelia (PTS). However, three‐dimensional (3D) visualization studies of PTS have been limited due to the lack of reliable 3D imaging techniques. In this study, the imaging efficiency of propagation‐based synchrotron radiation microtomography (PB‐SRµCT) was determined to detect the 3D morphology of the cavity and surrounding microvasculature network in a rat model of PTS. The rat model of PTS was established using the infinite horizon impactor to produce spinal cord injury (SCI), followed by a subarachnoid injection of kaolin to produce arachnoiditis. PB‐SRµCT imaging and histological examination, as well as fluorescence staining, were conducted on the animals at the tenth week after SCI. The 3D morphology of the cystic cavity was vividly visualized using PB‐SRµCT imaging. The quantitative parameters analyzed by PB‐SRµCT, including the lesion and spared spinal cord tissue area, the minimum and maximum diameters in the cystic cavity, and cavity volume, were largely consistent with the results of the histological assessment. Moreover, the 3D morphology of the cavity and surrounding angioarchitecture could be simultaneously detected on the PB‐SRµCT images. This study demonstrated that high‐resolution PB‐SRµCT could be used for the 3D visualization of trauma‐induced spinal cord cavities and provides valuable quantitative data for cavity characterization. PB‐SRµCT could be used as a reliable imaging technique and offers a novel platform for tracking cavity formation and morphological changes in an experimental animal model of PTS.     

Influence of low-intensity pulsed ultrasound on osteogenic tissue regeneration in a periodontal injury model: X-ray image alterations assessed by micro-computed tomography

Objective

This study was conducted to evaluate, with micro-computed tomography, the influence of low-intensity pulsed ultrasound on wound-healing in periodontal tissues.

Methods

Periodontal disease with Class II furcation involvement was surgically produced at the bilateral mandibular premolars in 8 adult male beagle dogs. Twenty-four teeth were randomly assigned among 4 groups (G): G1, periodontal flap surgery; G2, periodontal flap surgery + low-intensity pulsed ultrasound (LIPUS); G3, guided tissue regeneration (GTR) surgery; G4, GTR surgery plus LIPUS. The affected area in the experimental group was exposed to LIPUS. At 6 and 8 weeks, the X-ray images of regenerated teeth were referred to micro-CT scanning for 3-D measurement.

Results

Bone volume (BV), bone surface (BS), and number of trabeculae (Tb) in G2 and G4 were higher than in G1 and G3 (p < 0.05). BV, BS, and Tb.N of the GTR + LIPUS group were higher than in the GTR group. BV, BS, and Tb.N of the LIPUS group were higher than in the periodontal flap surgery group.

Conclusion

LIPUS irradiation increased the number, volume, and area of new alveolar bone trabeculae. LIPUS has the potential to promote the repair of periodontal tissue, and may work effectively if combined with GTR.     

Ethanol bone evaluation using 3D microtomography

The study of trabecular structures is important for understanding the mechanism of alcohol related to bone changes. Alcohol consumption can compromise the body mineral composition, affecting the bone metabolism and compromising the skeleton. The effects of the ethanol treatment on the internal microarchitecture of bone samples through 3D microcomputed tomography are shown in this study. The data was acquired from a radiographic system with a micro focus X-ray conic beam and it was used the Feldkamp's technique was used to carry out the 3D reconstructions. The measured microstructure parameters, which were based on stereological concepts, were bone volume fraction, relationship between bone surface and volume, trabecular number, separation and thickness. The results show that this technique is able to analyze these kinds of structures, especially rat bone, as these structures in rats (trabecular diameter) are thinner than in human bones.     

Rock porosity quantification by dual-energy X-ray computed microtomography

Porous media investigation by X-ray microtomography allows obtaining valuable quantitative and qualitative information, while preserving sample integrity. Modern X-ray nanotomography or Synchrotron radiation systems may distinguish structures sized only hundreds of nanometers. However, pores sized less than a few microns (microporosity) may be undetectable due to the system’s spatial resolution and noise in microfocus sources, compromising the quality of the measurement. In this study a dual-energy methodology was developed to generate density-based images from two scans made at two different voltages (80 kV and 130 KV) with a microfocus bench-top microtomography system. The images obtained were quantized in 256 gray levels, where the lowest value (zero) corresponded to voids and the highest value (255) corresponded to the densest regions mapped. From density images and single energy images, porosity was evaluated and compared. Results indicate that density images present better results than single energy images when both are compared with porosity obtained by the helium injection method. In addition, images acquired in dual-energy show good agreement with the sample’s real density values.     

Synchrotron radiation X-ray microfluorescence techniques and biological applications

Synchrotron X-ray imaging systems with fluorescence techniques was developed for biomedical researches in Brazilian Synchrotron Laboratory. An X-ray fluorescence microtomography system was implemented to analyse human prostate and breast samples and an X-ray microfluorescence system was implemented to study bone sites of human and animal samples with and without bone disorders.     

Analysing the sintering of heterogeneous powder structures by in situ microtomography

This work analyses the microstructure changes of various copper-based powder systems during sintering from 3D images provided by in situ synchrotron microtomography. The investigated systems include a copper powder with a wide particle size distribution of 0–63 µm poured into a quartz capillary, a pre-sintered copper compact with artificially created large pores and a mixture of copper and alumina particles. The experiments were carried out at the European Synchrotron in Grenoble, France. Powders were sintered up to 1060°C under reducing atmosphere in a furnace located between the X-ray source and the detector. During each experiment, 3D images were taken at various times of the thermal cycle. We have obtained images with a resolution of 1.5 µm and the time of acquisition of every image was ～1 min. Quantitative analysis of these images allowed the changes of various important parameters to be followed. Such parameters characterise the sintering process at the particle length scale: interparticle coordination, pore size distribution and particle centre-to-centre distance. Moreover, by tracking the displacement of each particle centre and comparing it to the displacement predicted by classical mean field assumption, we have been able to assess the magnitude of particle rearrangement occurring during sintering. From these data, the sintering behaviour of heterogeneous powder systems is discussed with particular emphasis of collective particle phenomena.     

Characterization of trabecular bone structure from high-resolution magnetic resonance images using fuzzy logic

The purpose of this work was to apply fuzzy logic image processing techniques to characterize the trabecular bone structure with high-resolution magnetic resonance images. Fifteen ex vivo high-resolution magnetic resonance images of specimens of human radii at 1.5 T and 12 in vivo high-resolution magnetic resonance images of the calcanei of peri- and postmenopausal women at 3 T were obtained. Soft segmentation using fuzzy clustering was applied to MR data to obtain fuzzy bone volume fraction maps, which were then analyzed with three-dimensional (3D) fuzzy geometrical parameters and measures of fuzziness. Geometrical parameters included fuzzy perimeter and fuzzy compactness, while measures of fuzziness included linear index of fuzziness, quadratic index of fuzziness, logarithmic fuzzy entropy, and exponential fuzzy entropy. Fuzzy parameters were validated at 1.5 T with 3D structural parameters computed from microcomputed tomography images, which allow the observation of true trabecular bone structure and with apparent MR structural indexes at 1.5 T and 3 T. The validation was statistically performed with the Pearson correlation coefficient as well as with the Bland-Altman method. Bone volume fraction correlation values (r) were up to .99 (P<.001) with good agreements based on Bland-Altman analysis showing that fuzzy clustering is a valid technique to quantify this parameter. Measures of fuzziness also showed consistent correlations to trabecular number parameters (r>.85; P<.001) and good agreements based on Bland-Altman analysis, suggesting that the level of fuzziness in high-resolution magnetic resonance images could be related to the trabecular bone structure.