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Jared Glover - One of the best experts on this subject based on the ideXlab platform.
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symmetrized bingham distribution for representing Texture Parameter estimation with respect to crystal and sample symmetries
Journal of Applied Crystallography, 2016Co-Authors: Stephen R Niezgoda, Eric A Magnuson, Jared GloverAbstract:The quaternion Bingham distribution has been used to model preferred crystallographic orientation, or crystallographic Texture, in polycrystalline materials in the materials science and geological communities. A primary difficulty in applying the Bingham distribution has been the lack of an efficient method for fitting the distribution Parameters with respect to the material's underlying crystallographic symmetry or any statistical sample symmetry due to processing. This paper presents a symmetrized distribution, based on the quaternion Bingham, which can account for any general combination of crystallographic or sample symmetries. A numerical scheme is also introduced for estimating the Parameters of the symmetrized distribution based on the well known expectation maximization algorithm.
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symmetrized bingham distribution for representing Texture Parameter estimation with respect to crystal and sample symmetries
arXiv: Materials Science, 2016Co-Authors: Stephen R Niezgoda, Eric A Magnuson, Jared GloverAbstract:The quaternion Bingham distribution has been used to model preferred crystallographic orientation, or crystallographic Texture, in polycrystalline materials in the materials science and geological communities. A primary difficulty in applying the Bingham distribution has been the lack of an efficient method for fitting the distribution Parameters with respect to the materials underlying crystallographic symmetry or any statistical sample symmetry due to processing. In this paper we present a symmetrized distribution, based on the quaternion Bingham, which can account for any general combination of crystallographic or sample symmetries. We also introduce a numerical scheme for estimating the Parameters of the symmetrized distribution based on the well known expectation maximization algorithm.
Didier Hans - One of the best experts on this subject based on the ideXlab platform.
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use of trabecular bone score tbs as a complementary approach to dual energy x ray absorptiometry dxa for fracture risk assessment in clinical practice
Journal of Clinical Densitometry, 2017Co-Authors: Enisa Shevroja, Olivier Lamy, Lynn Kohlmeier, Fjorda Koromani, Fernando Rivadeneira, Didier HansAbstract:Osteoporosis is a common bone disease characterized by low bone mass and altered bone microarchitecture, resulting in decreased bone strength with an increased risk of fractures. In clinical practice, physicians can assess the risk of fracture for a patient based on several risk factors. Some such as age, weight, and history of fractures after 50 years of age, parental fracture, smoking status, and alcohol intake are incorporated into FRAX, an assessment tool that estimates the 10-year probability of hip fracture and major osteoporotic fractures based on the individual's risk factors profile. The diagnosis of osteoporosis is currently based on bone mineral density (BMD) assessed by dual-energy X-ray absorptiometry scans. Among other widely recognized limitations of BMD is that BMD considers only the density of the bone and fails in measuring bone microarchitecture, for which novel techniques, such as trabecular bone score (TBS), have been developed. TBS is a Texture Parameter related to bone microarchitecture that may provide skeletal information that is not captured from the standard BMD measurement. Several studies have examined the value of TBS on predicting osteoporotic fractures. Our study aimed to summarize a review of the current scientific literature with focus on fracture risk assessment and to present both its findings and its conclusions regarding how and when TBS should be used. The existing literature indicates that low lumbar spine TBS is associated with a history of fracture and the incidence of new fracture. The effect is largely independent of BMD and of sufficient magnitude to enhance risk stratification with BMD. The TBS effect is also independent of FRAX, with likely greatest utility for those individuals whose BMD levels lie close to an intervention threshold. The clinical and scientific evidence supporting the use of TBS, with the ability of this technology to be seamlessly integrated into a daily workflow, makes TBS an attractive and useful clinical tool for physicians to improve patient management in osteoporosis. Further research is ongoing and necessary to further clarify the role of TBS in additional specific disorders.
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trabecular bone score tbs the new Parameter of 2d Texture analysis for the evaluation of 3d bone micro architecture status
Bone, 2011Co-Authors: Teddy Piveteau, Renaud Winzenrieth, Didier HansAbstract:X-ray is a technology that is used for numerous applications in the medical field. The process of X-ray projection gives a 2-dimension (2D) grey-level Texture from a 3- dimension (3D) object. Until now no clear demonstration or correlation has positioned the 2D Texture analysis as a valid indirect evaluation of the 3D microarchitecture. TBS is a new Texture Parameter based on the measure of the experimental variogram. TBS evaluates the variation between 2D image grey-levels. The aim of this study was to evaluate existing correlations between 3D bone microarchitecture Parameters - evaluated from μCT reconstructions - and the TBS value, calculated on 2D projected images. 30 dried human cadaveric vertebrae were acquired on a micro-scanner (eXplorer Locus, GE) at isotropic resolution of 93 μm. 3D vertebral body models were used. The following 3D microarchitecture Parameters were used: Bone volume fraction (BV/TV), Trabecular thickness (TbTh), trabecular space (TbSp), trabecular number (TbN) and connectivity density (ConnD). 3D/2D projections has been done by taking into account the Beer-Lambert Law at X-ray energy of 50, 100, 150 KeV. TBS was assessed on 2D projected images. Correlations between TBS and the 3D microarchitecture Parameters were evaluated using a linear regression analysis. Paired T-test is used to assess the X-ray energy effects on TBS. Multiple linear regressions (backward) were used to evaluate relationships between TBS and 3D microarchitecture Parameters using a bootstrap process. BV/TV of the sample ranged from 18.5 to 37.6% with an average value at 28.8%. Correlations' analysis showedthat TBSwere strongly correlatedwith ConnD(0.856≤r≤0.862; p<0.001),with TbN (0.805≤r≤0.810; p<0.001) and negatively with TbSp (−0.714≤r≤−0.726; p<0.001), regardless X-ray energy. Results show that lower TBS values are related to "degraded" microarchitecture, with low ConnD, low TbN and a high TbSp. The opposite is also true. X-ray energy has no effect onTBS neither on the correlations betweenTBS and the 3Dmicroarchitecture Parameters. In this study, we demonstrated that TBS was significantly correlated with 3D microarchitecture Parameters ConnD and TbN, and negatively with TbSp, no matter what X-ray energy has been used. This article is part of a Special Issue entitled ECTS 2011. Disclosure of interest: None declared.
Valérie Bousson - One of the best experts on this subject based on the ideXlab platform.
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Characterization of knee osteoarthritis-related changes in trabecular bone using Texture Parameters at various levels of spatial resolution-a simulation study.
BoneKEy reports, 2014Co-Authors: T Lowitz, Valérie Bousson, Oleg Museyko, Willi A Kalender, J D Laredo, Klaus EngelkeAbstract:Articular cartilage and subchondral bone are the key tissues in osteoarthritis (OA). The role of the cancellous bone increasingly attracts attention in OA research. Because of its fast adaptation to changes in the loading distribution across joints, its quantification is expected to improve the diagnosis and monitoring of OA. In this study, we simulated OA progression-related changes of trabecular structure in a series of digital bone models and then characterized the potential of Texture Parameters and bone mineral density (BMD) as surrogate measures to quantify trabecular bone structure. Five Texture Parameters were studied: entropy, global and local inhomogeneity, anisotropy and variogram slope. Their dependence on OA relevant structural changes was investigated for three spatial resolutions typically used in micro computed tomography (CT; 10 μm), high-resolution peripheral quantitative CT (HR-pQCT) (90 μm) and clinical whole-body CT equipment (250 μm). At all resolutions, OA-related changes in trabecular bone architecture can be quantified using a specific (resolution dependent) combination of three Texture Parameters. BMD alone is inadequate for this purpose but if available reduces the required Texture Parameter combination to anisotropy and global inhomogeneity. The results are summarized in a comprehensive analysis guide for the detection of structural changes in OA knees. In conclusion, Texture Parameters can be used to characterize trabecular bone architecture even at spatial resolutions below the dimensions of a single trabecula and are essential for a detailed classification of relevant OA changes that cannot be achieved with a measurement of BMD alone.
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a digital model to simulate effects of bone architecture variations on Texture at spatial resolutions of ct hr pqct and μct scanners
Journal of medical engineering, 2014Co-Authors: T Lowitz, Valérie Bousson, Oleg Museyko, Willi A Kalender, J D Laredo, Klaus EngelkeAbstract:The quantification of changes in the trabecular bone structure induced by musculoskeletal diseases like osteoarthritis, osteoporosis, rheumatoid arthritis, and others by means of a Texture analysis is a valuable tool which is expected to improve the diagnosis and monitoring of a disease. The reaction of Texture Parameters on different alterations in the architecture of the fine trabecular network and inherent imaging factors such as spatial resolution or image noise has to be understood in detail to ensure an accurate and reliable determination of the current bone state. Therefore, a digital model for the quantitative analysis of cancellous bone structures was developed. Five Parameters were used for Texture analysis: entropy, global and local inhomogeneity, local anisotropy, and variogram slope. Various generic structural changes of cancellous bone were simulated for different spatial resolutions. Additionally, the dependence of the Texture Parameters on tissue mineralization and noise was investigated. The present work explains changes in Texture Parameter outcomes based on structural changes originating from structure modifications and reveals that a Texture analysis could provide useful information for a trabecular bone analysis even at resolutions below the dimensions of single trabeculae.
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Trabecular bone score (TBS): available knowledge, clinical relevance, and future prospects
Osteoporosis International, 2012Co-Authors: Valérie Bousson, Catherine Bergot, Bjorn De Sutter, Pierre Levitz, Bernard CortetAbstract:The diagnosis of osteoporosis rests on areal bone mineral density (BMD) measurement using DXA. Cancellous bone microarchitecture is a key determinant of bone strength but cannot be measured using DXA. To meet the need for a clinical tool capable of assessing bone microarchitecture, the TBS was developed. The TBS is a Texture Parameter that evaluates pixel gray-level variations in DXA images of the lumbar spine. The TBS variations may reflect bone microarchitecture. We explain the general principles used to compute the TBS, and we report the correlations between TBS and microarchitectural Parameters. Several limitations of the TBS as it is used now are pointed out. We discuss data from currently available clinical studies on the ability of the TBS to identify patients with fractures and to evaluate the fracture risk. We conclude that this new index emphasizes the failure of the BMD T-score to fully capture the fragility fracture risk. However, although microarchitecture may influence the TBS, today, to the best of our understanding, there is no sufficient evidence that a TBS measurement provides reliable information on the status of the bone microarchitecture for a given patient. The TBS depends on gray-level variations and in a projectional image obtained in vivo, these variations can have many causes. Nevertheless, as clinical studies suggest that the TBS predicts the risk of fracture even after adjustment for BMD, we are encouraged to learn more about this score. Additional studies will have to be performed to assess the advantages and limitations of the TBS, in order to ensure that it is used appropriately in clinical practice.
Bernard Cortet - One of the best experts on this subject based on the ideXlab platform.
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Trabecular bone score (TBS): available knowledge, clinical relevance, and future prospects
Osteoporosis International, 2012Co-Authors: Valérie Bousson, Catherine Bergot, Bjorn De Sutter, Pierre Levitz, Bernard CortetAbstract:The diagnosis of osteoporosis rests on areal bone mineral density (BMD) measurement using DXA. Cancellous bone microarchitecture is a key determinant of bone strength but cannot be measured using DXA. To meet the need for a clinical tool capable of assessing bone microarchitecture, the TBS was developed. The TBS is a Texture Parameter that evaluates pixel gray-level variations in DXA images of the lumbar spine. The TBS variations may reflect bone microarchitecture. We explain the general principles used to compute the TBS, and we report the correlations between TBS and microarchitectural Parameters. Several limitations of the TBS as it is used now are pointed out. We discuss data from currently available clinical studies on the ability of the TBS to identify patients with fractures and to evaluate the fracture risk. We conclude that this new index emphasizes the failure of the BMD T-score to fully capture the fragility fracture risk. However, although microarchitecture may influence the TBS, today, to the best of our understanding, there is no sufficient evidence that a TBS measurement provides reliable information on the status of the bone microarchitecture for a given patient. The TBS depends on gray-level variations and in a projectional image obtained in vivo, these variations can have many causes. Nevertheless, as clinical studies suggest that the TBS predicts the risk of fracture even after adjustment for BMD, we are encouraged to learn more about this score. Additional studies will have to be performed to assess the advantages and limitations of the TBS, in order to ensure that it is used appropriately in clinical practice.
H. Yoneshima - One of the best experts on this subject based on the ideXlab platform.
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Age-related normative values of trabecular bone score (TBS) for Japanese women: the Japanese Population-based Osteoporosis (JPOS) study
Osteoporosis International, 2015Co-Authors: M. Iki, J. Tamaki, Y. Sato, R. Winzenrieth, S. Kagamimori, Y. Kagawa, H. YoneshimaAbstract:Trabecular bone score (TBS), a surrogate measure of bone microarchitecture, represents fracture risk independently of bone density. We present normative TBS values from a representative population study of Japanese women. This database would enhance our understanding of trabecular bone microarchitecture and improve osteoporosis management. Introduction TBS is a Texture Parameter that quantifies local variation in gray level distribution within dual-energy X-ray absorptiometry (DXA) images of the lumbar spine. While TBS is associated with fracture risk independently of areal bone mineral density (aBMD), normative TBS values have only been reported for Caucasian women. This study provides age-specific normative values of TBS from a representative sample of Japanese women. Methods We randomly selected 4,550 women aged 15–79 years from 7 areas throughout Japan. Women younger than 20 years and those with any medical history which might affect bone metabolism were excluded, and the remaining 3,069 with at least two assessable vertebrae from the first to the fourth vertebrae were subjected to analysis. TBS values were calculated from spine DXA images using TBS iNsight software (Med-Imaps, France). Age-related models of TBS were constructed using piecewise linear regression analysis. Results Participant age, body mass index (BMI), spine aBMD, and TBS (mean ± SD) were 48.7 ± 16.8 years, 22.9 ± 3.4, 0.888 ± 0.169 g/cm^2, and 1.187 ± 0.137, respectively. A three-piece linear regression model of TBS on age explained 70.7 % of the total variance in TBS and comprised very small age-related changes in the youngest segment of the regression line, rapid loss in the middle segment, and small loss in the oldest segment. TBS was lower in Japanese women than in Caucasian women across all age ranges, with the difference increasing with age up through 65 years. Conclusions The normative values of TBS for Japanese women presented here would enhance our understanding of trabecular bone microarchitecture and help improve the management of osteoporosis.
