"The goal of this thesis work has been to investigate improved diagnostic methods for both detecting osteoporosis and estimating fracture risk non-invasively, by assessing bone mass density (BMD) and bone microstructure. It evaluates new approaches for analyzing through-transmission ultrasound signals using coral samples as models for trabecular bone. The results of BUA, impulse response of coral samples and the angular decorrelation function of coral samples indicate that these ultrasound parameters may be useful in detecting changes in both bone mineral density (BMD) and the presence of dominant trabecular bone structure axis. "

Osteoporosis is a common bone disease that increases risk of low-trauma fractures associated with substantial morbidity, mortality, and financial costs. Clinically, osteoporosis is defined by low bone mineral density (BMD). BMD explains approximately 60-70% of the variance in bone strength. The remainder is due to the cumulative and synergistic effects of other factors, including trabecular and cortical bone micro-architecture. In vivo quantitative characterization of trabecular bone (TB) micro-architecture with high accuracy, reproducibility, and sensitivity to bone strength will improve our understanding of bone loss mechanisms and etiologies benefitting osteoporotic diagnostics and treatment monitoring processes. The overall aim of the Ph.D. research is to design, develop and evaluate new 3-D imaging processing algorithms to characterize the quality of TB micro-architectural in terms of topology, orientation, thickness and spacing, and to move the new technology from investigational research into the clinical arena. Two algorithms regarding to this purpose were developed and validated in detail - (1) star-line-based TB thickness and marrow spacing computation algorithm, and (2) tensor scale (t-scale) based TB topology and orientation computation algorithm. The TB thickness and marrow spacing algorithm utilizes a star-line tracing technique that effectively accounts for partial voluming effects of in vivo imaging with voxel size comparable to TB thickness and also avoids the problem of digitization associated with conventional algorithms. Accuracy of the method was examined on computer-generated phantom images while the robustness of the method was evaluated on human ankle specimens in terms of stability across a wide range of resolutions, repeat scan reproducibility under in vivo condition, and correlation between thickness values computed at ex vivo and in vivo resolutions. Also, the sensitivity of the method was examined by its ability to predict bone strength of cadaveric specimens. Finally, the method was evaluated in an in vivo human study involving forty healthy young-adult volunteers and ten athletes. The t-scale based TB topology and orientation computation algorithm provides measures characterizing individual trabeculae on the continuum between perfect plate and perfect rod as well as individual trabecular orientation. Similar to the TB thickness and marrow spacing computation algorithm, accuracy was examined on computer-generated phantoms while robustness of the algorithm across ex vivo and in vivo resolution, repeat scan reproducibility, and the sensitivity to experimental mechanical bone strength were evaluated in a cadaveric ankle study. And the application of the algorithm was evaluated in a human study involving forty healthy young-adult volunteers and ten patients with SSRI treatment. Beside these two algorithms, an image thresholding algorithm based on the class uncertainty theory is developed to segment TB structure in CT images. Although the algorithm was developed for this specific application, it also works effectively for general 2-D and 3-D images. Moreover, the class uncertainty theory can be utilized as adaptive information in more sophisticated image processing algorithms such as Snakes, ASMs and graph search.

Diss. (sammanfattning) Umeå : Umeå universitet, 2009. / Härtill 4 uppsatser. Även tryckt utgåva.

L'étude de l'os est d'un intérêt majeur en Anthropologie. Constituant la charpente des vertébrés, le squelette est le reflet de l'activité motrice. En effet, chaque élément du squelette a une fonction dictée par sa forme et un rôle autorisé par sa morphologie. C'est l'illustration la plus visible de l'adaptation. Ce processus est largement étudié dans la lignée humaine et ce dogme est au cœur de nombreuses recherches en Anthropobiologie. Ces caractères sont inscrits dans la forme de l'os. Chaque courbure, apophyse ou crête témoignent au moins en partie de l'action d'un muscle ou d'une fonction dictée par un lent processus évolutif voire adaptatif. Cette évolution se fait par l'évolution de caractères externes de l'os par sa forme ou l'anatomie " visible " d'une part et par l'évolution de caractères plus internes, subtils et directement lié aux propriétés biomécaniques de l'os à savoir l'os trabéculaire. L'os trabéculaire est un matériau plus fragile, déformable que l'os cortical. Il constitue une trace indirecte des contraintes appliquées squelette. C'est ainsi que les activités locomotrices, alimentaires ou occupationnelle seront inscrite dans l'endostructure osseuse. C'est la théorie développée par Wolff dès 1870 dans " The law of bone remodelling ". Il développa cette conception d'un processus actif, évolutif par l'observation macroscopique des travées de l'extrémité supérieure du fémur chez l'homme. Si la contrainte exercée sur un os en particulier augmente, il va se remodeler pour devenir plus rigide et résister à la charge dans ce segment d'os particulier et pour cette force particulière de contrainte. Nous avons étudié cette théorie sur deux modèles chez le vivant au niveau du membre supérieur et au niveau du membre inférieur pour caractériser les contraintes asymétriques appliquées à l'os trabéculaires. La latéralité ou préférence manuelle est un exemple d'activité asymétrique. Ses effets sur l'os sont bien connus lors de la pratique de sports intensifs ou d'activités très latéralisées. Cependant peu de données existent sur les activités usuelles et la préférence manuelle de l'homme jeune sans activité particulière. Par une étude en microscanner avec des coupes de 41 microns, des volumes d'intérêt dans les os du squelette carpien radial ont été réalisés sur des individus d'âge jeune sans antécédent particulier de façon bilatérale. Plusieurs variables cliniques et anthropométriques ont également été recueillis. Nous avons pu mettre en évidence des caractères endostructuraux expliquant la variabilité interindividuelles en les comparant avec des éléments anthropomorphiques et la force de serrage manuelle. Par ailleurs, les défauts d'axe en varus ou en valgus exercent des contraintes asymétriques également sur les articulations portantes. La chirurgie prothétique du genou croit ces dernières années de façon exponentielle par un effet conjoint de l'amélioration des techniques, et l'augmentation de l'incidence de l'arthrose. / The study of bone is of major interest in Anthropology. The skeleton is an image of motor activity. Indeed, every element of the skeleton has a function dictated by its shape and role and then by its morphology. This illustrates the most visible adaptation of the bone. This process is widely studied in the human lineage. This theory is an important path of research in Anthropology. These characters are inscribed in the shape of the bone. Each curve, or crest reflect the action of a muscle or a function dictated by a slow evolutionary process. This change is by changing external characteristics of the bone by its form or anatomy "visible" on the one hand and by the evolution of more internal character, subtle and directly related to the biomechanical properties of bone namely trabecular bone. Trabecular bone is a more brittle material, deformable than cortical bone. It is an indirect trace of the stresses applied to the bone. Thus locomotion, feeding or occupational activities can be analyzed into the bone endostructure. This is the theory developed by Wolff in 1870 in "The law of bone remodeling." He developed this idea of ??an active, evolving process by macroscopic observation of the spans of the proximal femur in humans. If the stress on a particular bone increases, it will remodel to become more rigid and withstand the load in that particular bone segment and for this particular force of constraint. We studied this theory on two models in the living human being. One concerned the upper limb and the second the lower limb to characterize asymmetrical forces on trabecular bone. Laterality or handedness is an example of asymmetrical activity. Its effects on bone are well known in the practice of intensive sports or very lateralized activities. However, little data exist on the usual activities and the handedness of the young man with no particular activity. We performed a microCT study with cuts 41 microns slices. Volumes of interest in radial carpal bones were performed on both sides on young human adults without particular medical history. Several clinical and anthropometric variables were also collected. We were able to highlight endostructural patterns explaining the interindividual variability in comparison with anthropometric parameters and crush or pinch grip. Furthermore, axis deviations in varus or valgus exert asymmetric constraints also on weight-bearing joints. The prosthetic knee surgery increases exponentially in the last decades by a combined effect of improved techniques and the increased incidence of osteoarthritis. The OA is multifactorial but the weight has a major effect on cartilage wear. We further know that the morphology and deformation of members influence this phenomenon. We wanted to characterize the response of the bone to endostructure these asymmetrical stresses on the tibial plateau. We collected tibial plateaus during total joint replacement surgeries for knee and compare the bone under chondral internal and external with microCT 7.4 micron slices. Some parameters highlight the major effect weight and body mass such as bone volume fraction BV/TV, structure model index SMI, trabecular space Tb. and trabecular number Tb.N. Subchondral densification during osteoarthritis is associated with a reduction in its elastic modulus, which could increase cartilage stress, and accelerate cartilage loss.

A caracterização de tecido ósseo por ultra-som para o diagnóstico de osteoporose tem sido investigada como uma alternativa a densitometria óssea baseada em radiação ionizante. A interação do ultra-som com o tecido ósseo é fundamentalmente diferente da que ocorre com a energia ionizante. O potencial da técnica ultra-sônica baseia-se nos efeitos sobre a propagação do campo acústico causados pela estrutura, composição e massa do tecido que está sendo investigado. Quatro estudos in-vitro e um estudo clínico estão descritos neste trabalho. O primeiro estudo in-vitro compara a correlação entre medidas ultra-sônicas e de densidade mineral óssea (em g/cm3) em tecido trabecular humano e bovino. A velocidade e atenuação ultra-sônicas em amostras ósseas foram determinadas pela técnica de inserção convencional (modo de transmissão) e a medida de densidade mineral óssea foi realizada por absortometria de um fóton (SPA). O mecanismo de interação do ultra-som com osso trabecular é pouco conhecido. O segundo estudo in-vitro investigou como a presença da medula óssea afeta as medidas de velocidade e atenuação. As correlações entre medidas ultrasônicas e de densidade mineral óssea (em g/cm3) por SPA, com e sem a presença da medula óssea, são também determinadas. A medida ultra-sônica de inserção convencional é comparada a medida de inserção por contato. O terceiro estudo in-vitro investigou em amostras de calcâneo as correlações entre medidas ultra-sônicas e de densidade mineral óssea (em g/cm3 e em g/cm2) por SPA. A determinação da densidade mineral Óssea em g/cm2 (BMD) a partir de medidas ultra-sônicas nas amostras foi pela primeira vez investigada, utilizando-se uma técnica de regressão linear univariável e multivariável e uma técnica multivariável não-linear baseada em redes neurais. Um novo parâmetro, baseado na média da frequência instantânea (MIF) do sinal da amostra e de referência, foi proposto para caracterizar o tecido ósseo devido a sua alta correlação com a atenuação. O efeito das corticais ósseas do calcâneo nas medidas ultra-sônicas é pouco conhecido. O quarto estudo in-vitro determinou a correlação entre medidas ultrasônicas e de densidade mineral óssea (em g/cm3) por SPA, com e sem a presença das corticais ósseas. Finalmente, no estudo clínico foram determinadas as correlações entre medidas ultra-sônicas no calcanhar e de densidade mineral óssea por DEXA (em g/cm2) no cólo femoral. A determinação da densidade óssea a partir de medidas ultra-sônicas no calcanhar foi pela primeira vez investigada, utilizando-se uma técnica de regressão linear univariável e multivariável e uma técnica multivariável não-linear baseada em redes neurais. / Ultrasonic assessment of bone for managing osteoporosis has been investigated as an alternative to radition-based bone densitometry technology. In contrast with the ionizing electromagnetic radiation of such clinical bone densitometric technique, ultrasound is a mechanical wave and thus interacts with bone in a fundamentally distinct manner. Ultrasound is viewed as having great potential for assessing bone since its propagation is affected by the structure, composition, and mass of the bone tissue being interrogated. Four in-vitro and one clinical study are reported in this work. In the first in-vitro study a comparison is reported on the ultrasonic assessment of human trabecular and bovine trabecular bone samples. Both ultrasonic velocity and attenuation were evaluated through a standard transmission insertion technique and correlated with bone mineral density (in g/cm3 ) as determined with single photon absorptiometry (SPA). There is a relatively limited understanding of how ultrasound interacts with cancellous bone. One potentially model leads analytically to the demonstration that ultrasound propagation through bone is dependent on several factors, including the properties of the fluid, which saturates the pores of the cancellous bone tissue. The second in-vitro study was carried out to assess how the presence of marrow affects the velocity and attenuation measurements. The correlation between ultrasonic and densitometric measurements (in g/cm3) by SPA, with and without the bone marrow, are also determined. A second part of this study compared the measurements of ultrasonic attenuation and velocity on bovine cancellous bone samples using a standard insertion technique with those obtained using a contac method. The thrid in-vitro study with the calcis trabecular samples investigated the correlations between ultrasonic measurements and bone mineral density (in g/cm3 e em g/cm2) as measured by SPA. A nonlinear multivariate estimation technique based on neural network was the first time investigated to determine the ability of ultrasonic measurements to estimate bone mineral density in g/cm2 (BMD). A linear univariate and multivariate estimation of BMD was compared with the neural network approach. A new parameter to characterize the trabecular bone is been proposed, which is based on the mean instantaneous frequency (MIF) of the sample and reference signals after transmission through the os calcis. It was founded a high correlation between MIF and the attenuation (BUA). Little is known about the effect of the os calcis cortical shell on ultrasonic measurements. The fourth in-vitro study with os calcis samples determined the correlation between ultrasonic and densitometric measurements (in g/cm3) by SPA with and without the cortical shell. Finally, a nonlinear multivariate estimation technique based on neural network was the first time investigated to determine the ability of clinical ultrasonic measurements in the heel to estimate bone mineral density (BMD) in the femoral neck. A linear univariate and multivariate estimation to predict BMD in patients is also compared with the neural network approach.

A osteoporose é uma doença que afeta o tecido ósseo sendo caracterizada principalmente pela diminuição da massa óssea e pela deterioração da arquitetura do osso. O método atualmente utilizado no diagnóstico da osteoporose é a densitometria óssea (DEXA -Dual Energy X-ray Absorptiometry), que utiliza radiação ionizante. Vários estudos têm sido publicados discutindo o uso de técnicas complementares ou alternativas à densitometria óssea. Uma dessas técnicas é a ultrasonometria, que é baseada na análise da propagação do ultra-som para identificar a qualidade do tecido ósseo. O objetivo desse trabalho é contribuir com o acréscimo de dados para a avaliação da possibilidade de uso dessa técnica como alternativa à técnica da densitometria óssea. Foi realizado um estudo de correlação entre medidas experimentais em ossos trabeculares de calcâneos humanos obtidas com o equipamento de ultrasonometria óssea SONOST-2000 (Vicmed/OsteoSys-MedisonÒ) e medidas de ensaio mecânico de compressão. A microscopia eletrônica de varredura foi utilizada como um teste complementar para identificar as modificações na microarquitetura das amostras de ossos humanos sadios e osteopênicos. Os resultados indicam que o BQI (Bone Quality Index – Índice de Qualidade Óssea) pode ser usado como um método indireto de averiguação das importantes propriedades na determinação do risco de fratura, como por exemplo, a tensão máxima suportada pelo material. / Osteoporosis is a disease that affects bone tissue and is characterized by a decrease in its mass and deterioration of its architeture. The current method used in osteoporosis diagnostic is bone densitometry (DEXA- Dual Energy X-ray Absorption), which utilizes ionizing radiation. Various studies have been published discussing alternatives or complimentary techniques to bone densitometry. One of these techniques is quantitative untrasound (QUS), which is based on the analysis of ultrasound spread through bone tissue to assess its quality. The objective of this work is to add more data to the discussion of this technique as an alternative to bone densitometry. Correlation studies between data from experiments in trabecular bones from the calcaneus of human cadavers have been performed using the quantitative ultrasound equipment SONOST-2000 (Vicmed/OsteoSys-Medison) and mechanical compression essays. Scanning Electron Microscopy was also used as an aid to identify modifications in the samples microarchiteture from health and osteopenic tissue. The results indicate that BQI (Bone Quality Index ) can be used as indirect method to obtain important parameters used in the assessment of fracture risk, such as the maximum load supported by the material.

No description available.

No description available.

Ossos trabeculares possuem uma microestrutura porosa e podem ser modelados como um sólido elástico linear, heterogêneo e anisotrópico. A microtomografia tridimensional por raios-x (uCT) tem sido mundialmente utilizada para a caracterização de osso trabecular em pesquisas relacionadas à qualidade óssea e à doenças do metabolismo ósseo como a osteoporose. Na literatura há poucas investigações comparando as análises morfométricas 2D e 3D de osso trabecular. Nesta investigação amostras de osso trabeculares cilíndricas extraídas da cabeça femoral bovina foram utilizadas para a comparação dessas análises por \'mü\'CT. O software CT-Analyser foi utilizado para medidas em três direções (crânio-caudal, lateral-medial e anterior-posterior) de diversos parâmetros da microestrutura trabecular tais como espessura trabecular, separação trabecular, número trabecular e os autovalores do tensor de anisotropia (M). A comparação entre os valores dos parâmetros medidos por análises morfométricas 2D e 3D foi realizada pelo teste-t pareado com nível de significância p < 0,05 e por correlação linear de Pearson. Os autovalores da matriz M mostram que a microestrutura trabecular bovina tem uma tendência para a simetria transversalmente isotrópica. Os resultados obtidos mostram que a microtomografia tridimensional por raios-X é uma técnica de grande potencial para caracterização da qualidade óssea gerando bons parâmetros para o diagnóstico de doenças do metabolismo ósseo. / Trebecular bones have a porous microstructure and can be modeled as a linear elastic solid, heterogenous and anisotropic. The x-ray tridimensional microtomography (\'mü\'CT) has been worldwide used for the assessment of trabecular bone in investigations related to bone quality and aimed to the diagnostic of bone metabolic diseases such as osteoporosis. In the literature few investigations have compared the 2D and 3D morphometric analysis of trabecular bone. In this investigation cylindrical trabecular bone samples were harvested from bovine head femur to carry out that comparison by \'mü\'CT. The CT-Analyser software was used to measure in three directions (superior-inferior, lateral-medial and anterior-posterior) several microstructural trabecular parameters such as trabecular thickness, trabecular separation, trabecular number and the eigenvalues of the fabric tensor (M). The comparison between the parameters values measured by 2D and 3D morphometric analysis was performed by the paired-sample t test with a level of significance p < 0,05 and the Pearson\'s linear correlation. The eigenvalues show that the bovine trabecular microstructure has a tendence to transverse isotropy symmetry. The results show that x-ray tridimensional microtomography (\'mü\'CT) is a technique of great potential for characterization of generating good bone quality parameters for the diagnosis of diseases of bone metabolism.

Cette thèse présente l’apport d’une analyse fractale de la texture de l’os trabéculaire sur des clichés de radiographie du genou pour la caractérisation de la gonarthrose. Dans un premier temps cette analyse de texture a été confrontée aux méthodes actuelles de suivi de la pathologie afin de valider leur intérêt dans le suivi clinique des patients. Un second temps a été consacré à la prédiction de l’initiation de la pathologie où aucun marqueur ne fait référence. L’analyse de texture a été menée en utilisant des approches fractales permettant de s’affranchir des problèmes de variation d’acquisition entre différents centres cliniques tout en comparant différentes méthodes de calcul. La texture osseuse trabéculaire a été analysée à différentes plages d’échelle afin de caractériser les mécanismes sous-jacents de modification de la microarchitecture osseuse induits par la gonarthrose. Nous avons pu mettre en évidence l’intérêt prédictif de cette analyse peu coûteuse et largement accessible dans le cadre aussi bien de l’initiation que de la progression de l’arthrose du genou. / This thesis presents the contribution of the trabecluar bone texture fractal analysis on knee radiographs for the knee osteoarthritis characterization. Firstly, this texture analysis was confronted to the actual methods of the pathology clinical monitoring in order to validate their interest in the patients monitoring. Secondly, the prediction of the knee osteoarthritis initiation was investigated, domain in which there are still no markers defined. The texture analysis was performed using fractal approaches avoiding the problems of the variations in the acquisition among different clinical centers and comparing different computing methods. Trabecular bone texture was analyzed at different ranges of scale in order to characterize the underlying mechanisms of the microarchitecture modification induced by the knee osteoarthritis. Thus, we highligthed the predictive interest of this cheap and largely available analysis for both the initiation and the progression of the knee osteoarthritis.