Three-Dimensional (3D) Microarchitecture Correlations with 2D Projection Image Gray-Level Variations Assessed by Trabecular Bone Score Using High-Resolution Computed Tomographic Acquisitions: Effects of Resolution and Noise

The aim of the present study is to determine the level of correlation between the 3-dimensional (3D) characteristics of trabecular bone microarchitecture, as evaluated using microcomputed tomography (mu CT) reconstruction, and trabecular bone score (TBS), as evaluated using 2D projection images directly derived from 3D mu CT reconstruction (TBS mu CT). Moreover, we have evaluated the effects of image degradation (resolution and noise) and X-ray energy of projection on these correlations. Thirty human cadaveric vertebrae were acquired on a microscanner at an isotropic resolution of 93 mu m. The 3D microarchitecture parameters were obtained using MicroView (GE Healthcare, Wauwatosa, MI). The 2D projections of these 3D models were generated using the Beer-Lambert law at different X-ray energies. Degradation of image resolution was simulated (from 93 to 1488 mu m). Relationships between 3D microarchitecture parameters and TBS mu CT at different resolutions were evaluated using linear regression analysis. Significant correlations were observed between TBS mu CT and 3D microarchitecture parameters, regardless of the resolution. Correlations were detected that were strongly to intermediately positive for connectivity density (0.711 <= r(2) <= 0.752) and trabecular number (0.584 <= r(2) <= 0.648) and negative for trabecular space (-0.407 <= r(2) <= -0.491), up to a pixel size of 1023 mu m. In addition, TBS mu CT values were strongly correlated between each other (-0.77 <= r(2) <= 0.96). Study results show that the correlations between TBS mu CT at 93 mu m and 3D microarchitecture parameters are weakly impacted by the degradation of image resolution and the presence of noise.