Papers by Keyword: Micro Computed Tomography (μ-CT)

Abstract: Calcium phosphate ceramics are widely used as bone substitutes since they are biocompatible and bioactive. Having a chemical composition close to natural bone, calcium phosphate ceramics are promising bone substitute materials in orthopaedics, maxillofacial surgery and dentistry. Hydroxyapatite (HA) and tricalcium phosphate (TCP) are the most commonly used calcium phosphates, because their calcium/phosphorus (Ca/P) ratios are close to that of natural bone and they are relatively stable in physiological environment. HA is a major constituent of bone materials and is resorbed after a long time of residence in the body. In this work, highly porous hydroxyapatite scaffolds were produced by polymer replication method and their properties evaluated by Scanning Electron Microscopy (SEM) and micro computerized tomography ()-CT).

Abstract: We have developed a new Ti alloy, Ti-15%Zr-4%Nb-4%Ta alloy (Ti-15-4-4) that showed higher biological safety and mechanical properties than the currently used Ti-6%Al-4%V alloy. The purpose of this study is to determine the biological performance of the new alloy. Ti-15-4-4 implants (machined or blasted) were placed in surgically created defects in rabbit femurs. The rabbits were sacrificed after 4, 8, 16, 24 and 48 weeks. Bone mineral density (BMD) and area of newly formed bone around the implants were measured using micro-CT. Results showed that the Ti-15-4-4 alloy is biocompatible and forms new bone around the Ti-15-4-4 implant, regardless of the surface treatment. The BMD and area of newly formed bone around the blasted implant surfaces were significantly greater than those around the machined surfaces. These results indicate that the new Ti-15-4-4 alloy has a potential for use as implants and has the advantage of improved mechanical properties described in earlier studies.

Abstract: In order to develop bone substitute with osteogenic properties, a novel strategy of grafting cyclo-DfKRG peptides to enhance cells adhesion and osteointegration of hydroxyapatite (HA) implants was developed. Objectives of the study were (1) to evaluate the osteogenic properties of HA implants grafted with RGD peptides and (2) to compare histomorphometry and micro-computed tomography ((CT) with bone quantification. Pure HA grafted or not with cyclo- DfKRG peptides and autologous stromal cells was implanted in femoral condyle on 2 groups (2 and 4 weeks) of 6 New Zealand rabbits. Measurements concerning bone reconstruction and material structure were obtained with a (CT and the results were compared to those obtained after histomorphometry. Finally, it appears that grafting cyclo-DfKRG on HA implants enhances nonsignificantly the rate of bone formation, and a high correlation of the results was found comparing histomorphometry and (CT analysis.

Abstract: In order to investigate effects of low energy laser peening (LP) without protective coating on surface fatigue crack growth behavior, rotating bending fatigue tests were carried out on cast Al-Si-Mg aluminum alloy with a pre-cracked round bar type specimens. As the results, the fatigue crack growth was restrained by the compressive residual stress induced by laser peening treatment. And also, the three dimensional (3D) image of surface fatigue cracks was reconstructed by using a micro computed tomography (μCT) with phase contrast technique. It was also shown that the surface crack growth was restrained for the laser peened materials.

Abstract: To analyze the importance of bone quality, we studied 21 primary compressive trabecular system by micro-computed tomography(micro-CT), finite element analysis and destructive mechanical test. Significant correlations were found between histomorphometry and biomechanical parameters. The results indicate that the bone quality of primary compressive trabecular system is determined more by its combined micro-structural parameters (histomorphometry) and biomechanical parameters than histomorphometry only. Assessment of trabecular bone by finite element analysis may become important not only for assessment of bone quality but also for prediction of bone fracture risk of bone degeneration.

Abstract: Several researchers investigated the mechanical characteristics of human trabecular bone using finite element analysis (FEA) based on micro computed tomography (μ-CT). There were few investigations on morphological and mechanical characteristics of vertebral trabecular bones. This study analyzed the relationship between morphological and mechanical characteristics in the regional vertebral trabecular bones using μ-CT and μ-FEA. Two specimens were obtained from the 12th thoracic vertebral bodies of cadavers (85 years female and 48 years male). In each vertebral body, fifteen regions were selected from two-dimensional (2D) images acquired from μ-CT. Voxelbased three-dimensional (3D) finite element models, with 4
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4 cubic block, were generated from each region for simulated compression test. The relationship between morphological characteristics, such as bone volume fraction, trabecular thickness, trabecular separation, trabecular number and structure model index, and mechanical characteristics, such as structural modulus (E†), was analyzed by bivariate correlation coefficient. As a result, the region of center column and inferior layer had the highest density. However, structural moduli in center column and middle layer were the biggest. The results indicated that there was a regional difference between morphological and mechanical characteristics of vertebral trabecular bone. In addition, for more exact evaluation of osteoporosis, it was recommended to analyze not only the mechanical characteristics but also the morphology characteristics.

Abstract: Considerable researchers analyzed the effects of hormone treatment on osteoporotic vertebral bones. Hormone treatment of age-related osteoporotic bone has a potential to decrease an incidence of osteoporosis. In the present paper, experimental and simulated tests for the mechanical characteristics of osteoporotic models and their hormone-treated models were investigated. Three dimensional (3D) geometries of the models (rapid prototyped and finite element models) were generated from high resolution micro-computed tomography ($-CT, Skyscan 1076, Skyscan, Belgium) scan data for the central parts of the second lumbar vertebrae. From these 3D geometries, cubic specimens with side length 6.5mm were formed and analyzed. Rapid prototyped (RP) models, instead of the real bone specimen, of vertebral trabecular bones were created in the fused deposition modeling (FDM) machine. In the present study, experimental compressions test for RP models were carried out by the INSTRON testing machine (8874 series, Instron, UK). The mechanical characteristics of finite element (FE) models for simulated compression tests were compared with physical predictions from RP models for experimental compression test. As a result, it is found that the hormone therapy is likely to be less effective than reported by previous researchers. A remarkable agreement was achieved between the results obtained from the experimental tests for RP models and simulated tests for FE models.

Abstract: Bone repair method has run to a new stage of bone tissue engineering. Doctors use bone scaffold to fill bone trauma and expect human regeneration ability to reconstruct bone trauma while bone is degrading. Scaffold is essential to bone tissue engineering. Scaffold should introduce new bone with scaffold’s conduction channel. But it’s still very difficult for scaffold to mimic fine structure of bone. Ideal scaffold should have similar component and microstructure to natural bone, which makes it more biocompatible and better to reconstructed bone. So we forward microCT aided design and preparation to solve this problem. MicroCT outputs both shape and three-dimensional internal density information. Then, we build computer model of scaffold with acquired microstructure. We fabricate scaffold that mimics natural bone by 3D rapid prototype machine.

Abstract: Porous calcium phosphate ceramics have been widely investigated in orthopaedic surgery as bone extensor. Attention has been given to manufacturing of a porous bioceramic that mimics the trabecular bone structure for proper bone regeneration and integration. Although different methods have been applied to manufacture the porous structure, it was unable to visualize the pores and their interconnections within the ceramic and had objective measurement of the calcium phosphate ceramics. With the advance of biomedical imaging through micro-computed tomography (microCT), the study attempted to quantify the pore structure of different calcium phosphate ceramics. Three kinds of bioceramic blocks, namely BSC, ChronOS, and THA, were synthesized by three methods and tested in the study. Six blocks of each bioceramic were evaluated by conventional water immersion method and microCT. The pore size and connectivity of the pores were evaluated with standardized protocols. The three-dimensional analysis of the pores and their distribution by microCT was presented. The ChronOS had more functional pores (200-400μm in diameter) than the BSC and THA did (p<0.05). Providing objective information on the functional pores, the microCT evaluation serves as a good standard for specification of the bioceramic-related implants.

Abstract: Hydroxyapatite/collagen (HAp/Col) composite scaffold with unidirectionally elongated pores (scaffold-U) was fabricated by the unidirectional solidification with ice growth and subsequent freeze-dry process. The pore architecture in the composite was evaluated by using scanning electron microscopy (SEM) and micro computed tomography (micro-CT) with a high resolution. The SEM observation showed that the scaffold-U had unidirectional pores elongated along the vertical direction (i.e. ice growth direction), however the horizontal cross-section showed quite different pore morphology: spindle-shaped pores with random direction. The 3-D micro-CT image of the scaffold-U simultaneously showed the microstructure of the unidirectionally elongated pore and the cross-sectional pore, indicating that the interconnected micropores were successfully fabricated along the ice growth direction. The micro-CT is a powerful tool for the visualization of 3-D pore structure.