Measurement of phosphorus content in normal and osteomalacic rabbit bone by solid-state 3D radial imaging

In osteomalacia decreased mineralization reduces the stiffness and static strength of bone. We hypothesized that hypomineralization in osteomalacic bone could be quantified by solid-state P-31 magnetic resonance imaging (SS-MRI). Hypomineralization was measured with a 3D radial imaging technique at 162 MHz (9.4T) in rabbit cortical bone of hypophosphatemic (HY) and normophosphatemic (NO) animals. The results were compared with those obtained by quantitative micro-CT (mu-CT) and P-31 solution NMR. 3D images of 277 mu m isotropic voxel size were obtained in 1.7 hr with SNR similar to 9. Mineral content was lower in the HY relative to the NO group (SS-MRI: 9.48 +/- 0.4 vs. 11.15 +/- 0.31 phosphorus wet wit %, P < 0.0001; mu-CT: 1114.6 +/- 28.3 vs. 1175.7 +/- 23.5 mg mineral/cm(3); p = 0.003). T, was shorter in the HY group (47.2 +/- 3.5 vs. 54.1 +/- 2.7 s, P = 0.004), which suggests that relaxation occurs via a dipole-dipole (DD) mechanism involving exchangeable water protons, which are more prevalent in bone from osteomalacic animals.