Bone mineral imaged in vivo by 31P solid state MRI of human wrists

PURPOSE: To implement solid state (31)P MRI ((31)P SMRI) in a clinical scanner to visualize bone mineral.
MATERIALS AND METHODS: Wrists of seven healthy volunteers were scanned. A quadrature wrist (31)P transmit/receive coil provided strong B(1) and good signal-to-noise ratio (SNR). A (1)H-(31)P frequency converter was constructed to enable detection of the (31)P signal by means of the (1)H 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 (31)P 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 ∼5.1 mm and SNR of 30 was obtained in 37 min. (31)P NMR properties (resonance line width 2 kHz and T(1) 17-19 s) of in vivo human bone mineral were measured.
CONCLUSION: In vivo (31)P 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 (31)P SMRI measurements on scanners which do not have multinuclear capability or for which the multinuclear receiver dead time is excessive.