Bone Mineral Imaged In Vivo by 31P Solid State MRI of Human Wrists

Purpose: To implement solid state P-31 MRI (P-31 SMRI) in a clinical scanner to visualize bone mineral. Materials and Methods: Wrists of seven healthy volunteers were scanned. A quadrature wrist P-31 transmit/receive coil provided strong B-1 and good signal-to-noise ratio (SNR). A H-1-P-31 frequency converter was constructed to enable detection of the P-31 signal by means of the H-1 channel. Data points lost in the receiver dead time were recovered by a second acquisition with longer dwell time and lower gradient strength. Results: Three-dimensional P-31 images, showing only bone mineral of the wrist, were obtained with a clinical 3 Tesla (T) scanner. In the best overall case an image with isotropic resolution of similar to 5.1 mm and SNR of 30 was obtained in 37 min. P-31 NMR properties (resonance line width 2 kHz and T-1 17-19 s) of in vivo human bone mineral were measured. Conclusion: In vivo P-31 SMRI visualization of human wrist bone mineral with a clinical MR scanner is feasible with suitable modifications to circumvent the scanners' limitations in reception of short-T-2 signals. Frequency conversion methodology is useful for implementing P-31 SMRI measurements on scanners which do not have multinuclear capability or for which the multinuclear receiver dead time is excessive.