O-17-DECOUPLED PROTON MR SPECTROSCOPY AND IMAGING IN A TISSUE MODEL

O-17-decoupled proton MR spectroscopy and imaging were implemented at 2 T. Their sensitivity and accuracy in vitro were examined using semis olid tissue phantoms doped with (H2O)-O-17. A double-tuned solenoidal coil was used to irradiate the same volume of O-17 and H-1 nuclei, as well as to facilitate direct calibration of the decoupling power. Deco upling efficiency was optimized as was O-17 detection sensitivity. Dec oupling was most efficient at RF amplitudes below 2.5 kHz (expressed a s gamma[O-17] x H-1), which is within the limits of the acceptable spe cific absorption rate. Propagation of error analysis demonstrated that O-17 detection sensitivity is optimal at a TE equal to the T-2 of O-1 7-depleted water protons. Based on Meiboom's work, a simple theory was formulated for estimating the transverse relaxivity of (H2O)-O-17 and the proton signal enhancement produced by decoupling. There was excel lent agreement between theory and experiment. Overall, O-17-decoupled spectroscopy and imaging were highly sensitive and accurate in quantif ying (H2O)-O-17 in vitro. (C) 1997 Academic Press.