Search

Objectives: The goal of this study was to examine the feasibility of in vivo imaging of trabecular bone around titanium implants by means of microfocus computed tomography (micro-CT) and the use of rabbits for this purpose., Materials and Methods: Ten male rabbits type Hollander, received a titanium implant (1.7 mm diameter and 10 mm length) in the trabecular bone of the left tibia. Seven weeks later a micro-CT scan was taken. Four rabbits were used to monitor potential harmful effects from X-ray absorption until 4 weeks after scanning. A second group of six rabbits was used for testing the hypothesis that a good correlation exists between in vivo micro-CT images and histological images of trabecular bone around titanium implants. The six rabbits were scanned and sacrificed immediately. The tibias were extracted and submitted to standard histological procedures. This resulted in a total of 12 histological sections and their corresponding 12 micro-CT images. Bone area measurements were performed at the left and right side of the implant in three regions: 0-500, 500-1000 and 1000-1500 microm distance from the implant interface. Intra-class correlations (ICC) were calculated between both techniques., Results: The four rabbits did not show any sign of radiodermatitis 4 weeks after scanning. In the micro-CT images of the group of six rabbits, trabeculae are visible, but not well defined, due to the presence of noise in the image. The ICC for the right implant side were 0.44 for zone 0-500 microm, 0.48 for zone 500-1000 microm and 0.40 for zone 1000-1500 microm. The ICC for the left implant side could not be calculated., Conclusion: A low agreement was found between the bone measurements from histology and in vivo micro-CT images. The use of the in vivo micro-CT for trabecular bone imaging around metallic implants should be restricted to track tendencies in follow-up studies.

A porous NiTi specimen prepared by self-propagating high temperature synthesis for bone implant applications has been characterised by a laboratory X-ray microtomography instrument to reveal the three-dimensional (3D) structure of the internal porosity. The reconstructed slices obtained from the tomography scan showed open porosity as well as micropores in the matrix. The 3D renderings revealed that the open porosity is highly interconnected, tortuous structure. 3D quantitative estimates of the micropores in terms of their volume fraction, number density and size have been evaluated. Metrics have been developed based on skeletonised idealisation of the complex architecture of interconnected pores that reflect its structural properties. [ABSTRACT FROM AUTHOR]

X-ray microfocus computed tomography (micro-CT) is recently put forward to qualitatively and quantitatively characterize the internal structure of porous materials. However, it is known that artifacts such as the partial volume effect are inherently present in micro-CT images, thus resulting in a visualization error with respect to reality. This study proposes a validation protocol that in the future can be used to quantify this error for porous structures in general by matching micro-CT tomograms to microscopic sections. One of the innovations of the protocol is the opportunity to reconstruct an interpolated micro-CT image under the same angle as the physical cutting angle of the microscopic sections. Also, a novel thresholding method is developed based on matching micro-CT and microscopic images. In this study, titanium porous structures are assessed as proof of principle. It is concluded for these structures that micro-CT visualizes 89% of the total amount of voxels (solid and pore) correctly. However, 8% represents an overestimation of the real structure and 3% are real structural features not visualized by micro-CT. When exclusively focusing on the solid fraction in both the micro-CT and microscopic images, only an overestimation of about 5% is found. [ABSTRACT FROM AUTHOR]

Abstract External resorptions associated with inflammation in marginal tissues present a difficult clinical situation. Many times, lesions are misdiagnosed and confused with caries and internal resorptions. As a result inappropriate treatment is often initiated. This paper provides three-dimensional representations of cervical external resorption, based on X-ray microfocus-tomographical scanning of a case, which will aid the dental practitioner in recognizing characteristic features during clinical inspection. In addition, histopathological examination reveals the cellular morphology of the adjacent tissues. [ABSTRACT FROM AUTHOR]

Abstract Aim The aim of this paper was to present an objective methodology for quantitative evaluation of root canal instrumentation using microcomputer tomography, together with developed software based on a constructed mathematical model. Methodology A desktop X-ray micro-CT scanner (SkyScan 1072) was used to provide data sets of an extracted mandibular molar before and after instrumentation (ProFile 0.04 Taper instruments, Dentsply Maillefer, Ballaigues, Switzerland) that were stored for later use by software. A volume visualization package (T3D) was applied to obtain 3D renderings of the molar to illustrate the qualitative visualization capacity. Next, medical image volume fusion software was used to allow alignment of pre and post image volumes. Finally, software was developed to make quantitative measurements and to provide additional qualitative information on the registered image volumes. This procedure implemented a true 3D mathematical model for quantification of instrumentation effects. Using a local co-ordinate frame, perpendicular reslices were made at five different levels within the mesio-buccal canal to evaluate transportation and centring ability. Results At first accurate and detailed 3D renderings were obtained. The general and local canal shape before and after preparation could visually be examined in 360° rotation. Numerical values were obtained for volume, volume changes and transportation. Centring ability was calculated by centring ratio and centre movement. Conclusions This methodology is a new and objective way for quantitative evaluation of root canal instrumentation using microcomputer tomography and dedicated software. [ABSTRACT FROM AUTHOR]

The article examines the Hounsfield values of selected bone sites on a computed tomography scan of the jaw and investigates the relationship between this radiological parameter and structural parameters. The method for measuring the parameters of bone samples from cadaver human jaws is described. It is concluded that the Hounsfield value in the jaw is not reliable for jaws with a thicker cortical layer.

Abstract: The morphology of soil pores is a crucial factor in the understanding of the ecology of soil microorganisms at a small scale. X-ray computer tomography (CT) enables to visualize the soil pore space in three dimensions. We aimed at exploring possible changes in porosity and pore morphology during the incubation of soil to which fresh residue was added. These changes were compared to changes in porosity and pore morphology in field aggregates. A set of CT images is presented from newly formed, incubated and field aggregates from both a sandy loam and a silt loam soil. These aggregates are about 6–8 mm diameter. After incubation of the artificial aggregates, we observed the formation of micro-cracks. At the same time, the total void porosity >27 μm increased from 3.5% to 7%. The pore size distribution indicated that this extra porosity was present in the 27–67 μm range. Furthermore, it was found that this new pore space was (partly) located near decomposing residue. To quantify the observed changes in pore morphology, we explored the use of the mass fractal dimension and variograms. After correction for differences in porosity, we found that incubation decreased the mass fractal dimension to the level of field aggregates in the sandy loam soil, while no differences were observed in the silt loam soil. In contrast, variogram parameters of the different treatments did not change consistently with the observations in both soils. In conclusion, the data suggest that microbial activity changes the morphology of the pore structure. However, the observed changes in the pore architecture were not sufficient to explain the large differences in aggregate stability among the analyzed samples. [Copyright &y& Elsevier]

This paper focuses on methods for generating a finite element model (FEM) based on in vivo microfocus computed tomography (μCT) images of guinea pig tibiae with a titanium percutaneous implant. A standard triangulated language (STL)-based approach was developed. Bone geometry was derived based on a pre-operative, metal artefact-free STL representation. Correct positioning of the implant with respect to the bone was implemented in a matching procedure of the post-operative bone representation onto the pre-operative representation. After further adaptation of the STL triangulation, it was converted into a tetrahedral FE mesh. To build FE models based on μCT-derived STL representations is a more efficient and accurate procedure than by implementing a CAD-based approach. The new STL-based procedure increases the usefulness of FE models as an interpretation tool for in vivo μCT images. In future work, these in vivo μCT-based finite element models will be used to implement algorithms that simulate adaptive bone response to controlled mechanical stimuli. [Copyright &y& Elsevier]

Load-bearing tissues, like bone, can be replaced by engineered tissues or tissue constructs. For the success of this treatment, a profound understanding is needed of the mechanical properties of both the native bone tissue and the construct. Also, the interaction between mechanical loading and bone regeneration and adaptation should be well understood. This paper demonstrates that microfocus computer tomography (μCT) based finite element modelling (FEM) can have an important contribution to the field of functional bone engineering as a biomechanical analysis tool to quantify the stress and strain state in native bone tissue and in tissue constructs. Its value is illustrated by two cases: (1) in vivo μCT-based FEM for the analysis of peri-implant bone adaptation and (2) design of biomechanically optimised bone scaffolds. The first case involves a combined animal experimental and numerical study, in which the peri-implant bone adaptive response is monitored by means of in vivo μCT scanning. In the second case μCT-based finite element models were created of native trabecular bone and bone scaffolds and a mechanical analysis of both structures was performed. Procedures to optimise the mechanical properties of bone scaffolds, in relation to those of native trabecular bone are discussed. [Copyright &y& Elsevier]

Two non-destructive tomographic techniques, X-ray CT imaging and magnetic resonance imaging (MRI), were applied to study the development of core breakdown disorder in ‘Conference’ pears (Pyrus communis cv. Conference). This disorder, which is characterized by brown discoloration of the tissue and development of cavities, is induced by elevated CO2 and decreased O2 levels during controlled atmosphere storage. Tomographic images of pears stored for 10 months under disorder inducing conditions, were acquired with both techniques and compared to the actual slices. Both X-ray and MRI were able to differentiate between unaffected tissue, brown tissue and cavities. A simple image-processing program, based on threshold values, was developed to determine the area percentage of affected and unaffected tissue as well as the cavity and core area per slice. For all three imaging techniques the area percentage brown tissue per slice increased with the diameter of the pear, but was systematically underestimated by 12% and 6% for, respectively, X-ray and MRI, compared to the actual slices. The area percentage cavity corresponded very well for all techniques. It was also found that the contours of the brown tissue were parallel to the fruit boundaries, suggesting a relation between the disorder symptoms and gas diffusion properties of the fruit. It was concluded that MRI is the most appropriate technique to study the development of core breakdown disorder during postharvest storage in future experiments. [Copyright &y& Elsevier]