Parallel plate model for trabecular bone exhibits volume fraction-dependent bias (original) (raw)
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A comparative study of trabecular bone micro-structural measurements using different CT modalities
Physics in Medicine and Biology, 2020
Osteoporosis, characterized by reduced bone mineral density and micro-architectural degeneration, significantly enhances fracture-risk. There are several viable methods for trabecular bone micro-imaging, which widely vary in terms of technology, reconstruction principle, spatial resolution, and acquisition time. We have performed an excised cadaveric bone specimen study to evaluate different CT-imaging modalities for trabecular bone microstructural analysis. Excised cadaveric bone specimens from the distal radius were scanned using micro-CT and four in vivo CT imaging modalities: HR-pQCT, dental CBCT, wholebody MDCT, and extremity CBCT. A new algorithm was developed to optimize soft thresholding parameters for individual in vivo CT modalities for computing quantitative bone volume fraction maps. Finally, agreement of trabecular bone micro-structural measures, derived from different in vivo CT imaging, with reference measures from micro-CT imaging was examined. Observed values of most trabecular measures, including trabecular bone volume, network area, transverse and plate-rod micro-structure, thickness, and spacing, for in vivo CT modalities were higher than their micro-CT-based reference values. In general, HR-pQCT-based trabecular bone measures were closer to their reference values as compared to other in vivo CT modalities. Despite large differences in observed values of measures among modalities, high linear correlation (r Î [0.94 0.99]) was found between micro-CT and in vivo CT-derived measures of trabecular bone volume, transverse and plate micro-structural volume, and network area. All HR-pQCT-derived trabecular measures, except the erosion index, showed high correlation (r Î [0.91 0.99]). The plate-width measure showed a higher correlation (r Î [0.72 0.91]) among in vivo and micro-CT modalities than its counterpart binary plate-rod characterization-based measure erosion index (r Î [0.65 0.81]). Although a strong correlation was observed between micro-structural measures from in vivo and micro-CT imaging, large shifts in their values for in vivo modalities warrant proper scanner calibration prior to adopting in multi-site and longitudinal studies.
Tissue Engineering Part C: Methods, 2011
Micro-computed tomography can be used to analyze subchondral bone features below treated cartilage defects in animal models. However, standardized methods for generating precise three-dimensional (3D) volumes of interest (VOI) below curved articular surfaces are lacking. The aims of this study were to develop standardized 3D VOI models adapted to the curved articular surface, and to characterize the subchondral bone specifically below a cartilage defect zone in intact and defect femoral trochlea. Skeletally mature rabbit distal femurs (N ¼ 8 intact; N ¼ 6 with acute debrided and microdrilled trochlear defects) were scanned by micro-computed tomography. Bone below the defect zone (3.5 mm width, 3.6 mm length, 1 mm deep) was quantified using simple geometric rectangular VOIs, and an optimized 3D VOI model with an adapted surface curvature, the Rectangle with Adapted Surface (RAS) model. In addition, a 250-mm-thick Curved-RAS model analyzed bone at three discrete subchondral levels. Simple geometric VOIs failed to analyze *17% of the tissue volume, mainly near the top of the curved trochlear ridges. The RAS models revealed that after debridement and drilling, only 31% of the original bone remained within the VOI and bone loss was mainly accounted for by surgical debridement. Adapted surface VOIs are better than simple geometric VOI shapes for quantifying structural features of subchondral bone below a curved articular surface. Structural differences between the bone plate and cancellous bone were best captured using the smaller, depth-dependent Curved-RAS model.
Bone, 2004
Stereological parameters have been used as an approximation for the architecture of trabecular bone. Structural indices such as bone volume fraction (BV/TV), trabecular number (Tb.N), trabecular thickness (Tb.Th), trabecular separation (Tb.Sp), bone surface-to-volume ratio (BS/BV), degree of anisotropy (MIL1/MIL3), and connectivity density (ÀEuler/Vol) have been widely studied to investigate pathological conditions in bone. Due to its high resolution and nondestructiveness, microcomputed tomography (micro-CT) has been utilized to take precise three-dimensional (3D) images of trabecular microstructures. However, spatial limitations for applying micro-CT-based analyses to large specimens, such as whole vertebral bodies, require using larger scanning and reconstruction voxel sizes.
Two and three-dimensional morphometric analysis of trabecular bone using X-ray microtomography (µCT)
Revista Brasileira de Engenharia Biomédica, 2014
Introduction: Trabecular bones have a porous microstructure and can be modeled as linear elastic solids, heterogeneous and anisotropic. In the literature, few investigations have compared the two-dimensional (2D) and three-dimensional (3D) morphometric analyses of cancellous bone. Methods: In this investigation eighteen cylindrical samples of cancellous bone (10 mm of diameter and 20 mm of height) were obtained from six bovine head femurs, with similar values for the weight and age, of the same race and gender. The samples were harvested and freezed at-20 °C before carrying out the microCT analysis. The CT-Analyzer software was used to measure in three directions (superior-inferior, lateral-medial and anterior-posterior) parameters such as trabecular thickness, trabecular separation, trabecular number and the eigenvalues of the fabric tensor (M). Results: The Comparison of 2D and 3D analyses for the parameters: 2D (plate model) trabecular thickness, trabecular separation and trabecular number were statistically different (p = 0) showing that measurements are not similar to the 3D ones. However, 2D (rod model) trabecular thickness and 3D trabecular thickness measurements presented no significant difference (p = 0.26). The eigenvalues show that the bovine trabecular microstructure has a tendency to transverserly isotropic symmetry. Discussion: The method proved to be quite interesting for the characterization of the bone structure through 3D measurements of trabecular bone morphometric parameters in the three possible directions of loading. The results show that x-ray microtomography (µCT) is a technique of great potential for characterization and generating bone quality parameters for the diagnosis of bone metabolism diseases.
Calcified Tissue International, 2005
The purpose of this study is to use high-resolution magnetic resonance (MR) imaging at 3 Tesla (3T) to quantify trabecular bone structure in vitro using femoral head specimens, and to correlate the calculated structure measures with those that were determined using microcomputed tomography (μCT), the standard of reference. Fifteen cylindrical cores were obtained from fresh femoral heads after total hip arthroplasty. MR images were obtained at 3T using a transmit-receive wrist coil. Highresolution coronal images were acquired using a modified three-dimensional (3D) fast-gradient echo sequence. From these data sets two-dimensional (2D) structural parameters analogous to bone histomorphometry were derived by using both mean intercept length (MIL) methods based on the plate model and the more recent model-assumption free 3D distance-transformation (DT) methods. The parameters measured by the 2D plate model-based MIL method and the DT method included apparent (App). BV/TV (bone volume/total volume), App. Tb.Th (trabecular thickness), App. Tb.Sp (trabecular separation), and App. Tb.N (trabecular number). Identical regions of interest were analyzed in the MR images and the μCT data sets, and similar structure measures were derived. The means and standard deviations of the parameters over all slices were calculated and MR-derived measures were correlated with those derived from the μCT data sets using linear regression analyses. Structure measures were overestimated with MRI, for example, the mean App. BV/TV was 0.45 for MRI and 0.20 for μCT, and the slope of the graph was 1.45. App. Tb.Th was overestimated by a factor of 1.9, whereas App. Tb.Sp was underestimated; Tb.N showed the smallest effect. Correlations between the individual parameters were excellent (App. BV/TV, r 2 = 0.82; App. Tb.Sp, r 2 = 0.84; App. Tb.N, r 2 = 0.81), except for App. Tb.Th (r 2 = 0.67). The results of this study show that trabecular bone structure measures may be obtained using 3T MR imaging. These measures, although higher than the standard of reference, show a highly significant correlation with true structure measures obtained by μCT.
Guidelines for assessment of bone microstructure in rodents using micro-computed tomography
Journal of Bone and Mineral Research, 2010
Use of high-resolution micro-computed tomography (mCT) imaging to assess trabecular and cortical bone morphology has grown immensely. There are several commercially available mCT systems, each with different approaches to image acquisition, evaluation, and reporting of outcomes. This lack of consistency makes it difficult to interpret reported results and to compare findings across different studies. This article addresses this critical need for standardized terminology and consistent reporting of parameters related to image acquisition and analysis, and key outcome assessments, particularly with respect to ex vivo analysis of rodent specimens. Thus the guidelines herein provide recommendations regarding (1) standardized terminology and units, (2) information to be included in describing the methods for a given experiment, and (3) a minimal set of outcome variables that should be reported. Whereas the specific research objective will determine the experimental design, these guidelines are intended to ensure accurate and consistent reporting of mCT-derived bone morphometry and density measurements. In particular, the methods section for papers that present mCT-based outcomes must include details of the following scan aspects: (1) image acquisition, including the scanning medium, X-ray tube potential, and voxel size, as well as clear descriptions of the size and location of the volume of interest and the method used to delineate trabecular and cortical bone regions, and (2) image processing, including the algorithms used for image filtration and the approach used for image segmentation. Morphometric analyses should be based on 3D algorithms that do not rely on assumptions about the underlying structure whenever possible. When reporting mCT results, the minimal set of variables that should be used to describe trabecular bone morphometry includes bone volume fraction and trabecular number, thickness, and separation. The minimal set of variables that should be used to describe cortical bone morphometry includes total cross-sectional area, cortical bone area, cortical bone area fraction, and cortical thickness. Other variables also may be appropriate depending on the research question and technical quality of the scan. Standard nomenclature, outlined in this article, should be followed for reporting of results. ß
Malaysian Journal of Fundamental and Applied Sciences, 2019
Micro-CT is one of the best modalities in assessing bone morphology and microarchitecture in small animal models. Voxel size is directly related to the image resolution as it influences the bone morphology results. The purpose of this study was to assess the effects of t different thicknesses of structures on the trabecular bone qualitative parameters. It was also to find out the most appropriate voxel size when scanning a certain or specific body part with different thicknesses. Five BALB-C breed mice carcasses were scanned using two different voxel sizes of 18 and 35 µm. The scanning acquisition times were recorded to be compared and the trabecular bone parameters measurements were taken. Both trabecular number and trabecular separation were increased in thicker structures meanwhile bone volume fraction and trabecular thickness values were inconsistent with the increment of the structure thickness. The bone volume fraction, trabecular thickness and trabecular separation were higher in larger voxel size and vice versa for trabecular number. The scanning acquisition time has no apparent correlation with the trabecular bone parameters. The thickness of the bone structure did affect trabecular number and trabecular separation significantly but less affecting bone volume fraction and trabecular thickness. All trabecular bone parameters were found affected by the size of scanning voxel size used. The usage of 35 µm voxel was more recommended than 18 µm to save time and give out less radiation dose to specimen unless the detailed features of the trabecular pattern was very important.
Morphometric analysis of trabecular bone thickness using different algorithms
Canadian Journal of Electrical and Computer Engineering, 2007
Investigations have been carried out with the goal of assessing the trabecular bone thickness of biological samples using images obtained by micro-computed tomography and magnetic resonance imaging. There is no conventional definition of trabecular bone thickness, and many methods may be involved in determining it. However, the results of the available algorithms or software packages differ considerably from each other. This paper determines trabecular bone thickness on the basis of several algorithms. A deep understanding of the performance of different methods is achieved by studying pseudo-three-dimensional images of both geometrical models of well-defined thickness and real bone samples with different bone densities. The models facilitate comparisons between the algorithms or software packages. Comparison of the results obtained from these commercial software packages and other state-of-the-art algorithms shows that the thickness, spatial distribution, and shape of an object affect each result differently, but in a significant manner. This is primarily due to variations in the thresholding algorithms used to distinguish object area elements (pixels/voxels) from the background, or non-object, region. Additionally, the results show that the average difference in thickness measurements can vary by up to 102.34% for models and 46.49% for real bone samples. This data shows that the differences in measurements of the trabecular bone thickness due simply to the algorithm involved are remarkable. Therefore, biomedical engineers and scientists should be careful to select the algorithm that is most compatible with their specific application. Cetteétude aété menée avec l'intention d'évaluer l'épaisseur d'os trabéculaireà partir d'échantillons acquis par micro tomographie et résonance magnétique. Il n'existe pas de définition conventionnelle de l'épaisseur de l'os trabéculaire. Aussi, plusieurs approches ontété envisagées en vue de caractériser cette dernière. Cependant il est apparu que les résultats obtenus différaient considérablement suivant les algorithmes ou logiciels commerciaux utilisés. Uneétude plus approfondie a doncété menée afin de déterminer les performances de chacune des méthodes, ceci au moyen d'étude faisant intervenir des modèles tridimensionnels numériques auxépaisseurs connues et d'os de différentes densités osseuses. Le recoursà l'utilisation de modèles a facilité la comparaison des différents algorithmes et logiciels. Cette comparaison a révélé que l'épaisseur, la répartition spatiale et la forme d'un objet affectaient de manière significative les résultats obtenus. Ceci fut principalement dûà la capacité des différentes approchesà discriminer l'objet a analyser (pixel/voxel) de l'information non pertinente, c'est-à-dire le fond de l'image. En outre, les résultats ont montré que les mesures d'épaisseur avaient une erreur moyenne maximale de 102.34% pour les modèles numériques et de 46.49% pour les spécimens d'os. Ces données ont indiqué que les différences de mesure d'épaisseur en raison des algorithmes utilisés sont significatives. Aussi, les ingénieurs bio-médicaux et les scientifiques en biomécanique devraientêtre très prudent quantà la sélection d'algorithmes morphométriques afin que ceux-ci soient les plus compatibles possibles avec leurs applications.
For comparative 3D lCT studies of trabecular bone, the use of a volume of interest (VOI) scaled to body size may avoid over-sampling the trabecular mass in smaller versus larger-bodied taxa and comparison of regions that are not functionally homologous (Fajardo and Mü ller: Am J Phys Anthropol 115 , though the influence on quantitative analyses using scaled versus nonscaled VOIs remains poorly characterized. We compare trabecular architectural properties reflecting mass, organization, and orientation from three volumes of interest (large, scaled, and small) obtained from the distal first metacarpal in a sample of Homo (n 5 10) and Pan (n 5 12). We test the null hypotheses that neither absolute VOI in Wiley Online Library (wileyonlinelibrary.com).