Osteoporosis is a bone disorder that manifests a decreased bone density and also deterioration in the cancellous bone architecture. Both factors increase bone fragility and the risk to suffering bone fractures, especially in women, due to their higher prevalence. The current diagnosis of osteoporosis consists in the quantification of the bone mineral density (BMD) by means of dual energy X-ray absorptiometry (DXA) techniques. However, BMD alone does not entirely account for fracture risk or therapeutic effects. Other factors such as the microstructural disposition of the trabeculae and their characteristics need also to be considered in order to determine bone quality and directly assess the fracture risk.
The technical advances of medical imaging modalities such as multi detector computed tomography (MDCT), high-resolution peripheral quantitative computed tomography (HR-pQCT) and magnetic resonance imaging (MRI) have allowed for the in vivo acquisitions at high spatial resolutions. The trabecular bone structure can be observed with good detail using these techniques.  In particular, the use of 3 Tesla (T) MR scanners has permitted the acquisitions at higher spatial resolutions. Furthermore, the good bone to marrow contrast obtained in MR images as well as the use of non-ionizing radiations set MRI as a suitable technique for the in vivo trabecular bone characterization in osteoporosis disease.  
In the present thesis, new methodological developments for a three-dimensional (3D) morphometry and mechanical characterization of the trabecular bone are proposed and applied to high resolution 3T MR acquisitions. The morphometry analysis is compound by different algorithms designed to quantify morphology, complexity, topology and anisotropy parameters of the trabecular tissue. Regarding the mechanical characterization, new methods for the automated simulation of the trabecular bone structure under compressive conditions and the calculation of the elastic modulus were developed. 
The developed methodology was applied to a population of healthy subjects in order to obtain normality values of the cancellous bone. The algorithms were also applied to a population of patients with osteoporosis in order to quantify the variations of the parameters due to the disease and evaluate the differences with the results obtained in an age-matched healthy group.
Finally, an evaluation of the reproducibility of the methods was performed by the calculation of the morphometry and mechanical parameters from repeated MR acquisitions performed to 5 sheep tibiae in three consecutive days. The validation of the measurements was also assessed by a comparison of the results with the same sheep tibiae acquired at higher spatial resolutions by micro computed tomography (µCT).
The proposed methodological developments and clinical applications provide satisfactory results, with a high sensitivity of the parameters to trabeculae variations mainly influenced by sex and the osteoporosis status. Furthermore, the methods present a high reproducibility and accuracy in the morphometry and mechanical parameters quantification. These results may reinforce the use of the presented parameters as imaging biomarkers of osteoporosis.