Evaluation of MRI resolution affecting trabecular bone parameters: determination of acceptable resolution.

The objective of this study is to evaluate the effect of MR image resolution on trabecular bone parameters and to determine the acceptable resolution that can be accurately analyzed to assess structural parameters. Ten distal femoral condyle specimens of 1 × 1 × 1 cm(3) were scanned with a 4.7-T Bruker BioSpec MRI scanner using a three-dimensional fast large-angle spin-echo sequence with various iso-cubic voxels sizes (65, 130, 160, 196, 230, and 260 μm). Otsu thresholding was applied to identify voxels containing bone. Conventional bone parameters, structural bone parameters, and skeleton-based local trabecular thickness (slTB.Th) were evaluated. The Bland-Altman method and correlation indicated that the conventional and structural bone parameters were preserved with an iso-cubic voxel size up to 230 μm (r > 0.932 and r > 0.843, respectively). In addition, slTB.Th derived from the highest resolution images (65 μm iso-cubic voxel size), correlated well (r > 0.833) with the values computed from lower resolution images, up to 230 μm, which is twice typical human trabecular thickness range (100-150 μm). The outcome of this study suggests that the various bone parameters were well preserved up to 230 μm images.