Angel Alberich Bayarri, Presenter: Nothing to Disclose

Waldir L Roque, Abstract Co-Author: Nothing to Disclose

Maria Angeles Perez, Abstract Co-Author: Nothing to Disclose

Luis Marti-Bonmati MD, PhD, Abstract Co-Author: Nothing to Disclose

High resolution 3T MR imaging can be used in the postprocessing and quantification of trabecular bone imaging biomarkers. However, its interpretation is intricate due to intrinsic heterogeneity. The aim of this work was to validate a bone mechanical competence parameter (MCP) for in vivo MR by combining morphology, connectivity, tortuosity and mechanical characteristics measured by comparison against microcomputed tomography (μCT).

A total of 103 subjects (75 healthy, 28 osteoporosis) were included in the MR study. For the μCT evaluation, a different dataset of 15 in vitro cadaveric samples from human radius was considered. The MR images from distal radius metaphysis were acquired in a 3T system (Philips, The Netherlands) with an isotropic resolution of 180μm. μCT spatial resolution was 34μm (Scanco, Switzerland). The MR sequence was a 3D T1 gradient echo (TE/TR/α=5ms/16ms/25). Images were properly processed and finally binarized to obtain 3D reconstructions. Morphology algorithms were applied to calculate bone-volume/total-volume (BV/TV) ratio, trabecular thickness (Tb.Th) and trabecular separation (Tb.Sp). The Euler-Poincaré Characteristic (EPC) to assess structure connectivity and trabeculae tortuosity (τ) were also analyzed. The 3D volumes were converted to Finite Element meshes to simulate uniaxial compression and calculate the elastic modulus (Eapp[X,Y,Z]). The correlations and variance of the biomarkers calculated for MR and μCT were analyzed by principal components analysis (PCA) in order to extract the relevant parameters in each modality and define the MCP.  

A first principal component was found explaining 95% of the variance, both in MR and μCT data. The first component had the same parameters and almost the same weights for MR (MCPMR=0.53·BV/TV-0.50·EPC+0.51·EappZ-0.45·τ) than for μCT (MCPμCT=0.52·BV/TV-0.49·EPC+0.51·EappZ-0.48·τ), which was considered as the reference.

The results of this study validate the importance of the bone percentage, the connectivity, tortuosity and Z elastic modulus in explaining bone properties, showing almost the same weighting in MR-derived measurements than in the reference μCT using different samples. This justifies the use of MR for a complete quantitative bone characterization in Osteoporosis.

Quantification of trabecular bone properties from MR can be used for the early evaluation of microstructural alterations in osteoporosis.

Alberich Bayarri, A, Roque, W, Perez, M, Marti-Bonmati, L, Validation of a Mechanical Competence Parameter for the Trabecular Bone Characterization from 3T-MR.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14018554.html