17O-decoupled proton MR spectroscopy and imaging in a tissue model.

17O-decoupled proton MR spectroscopy and imaging were implemented at 2 T. Their sensitivity and accuracy in vitro were examined using semisolid tissue phantoms doped with H2(17)O. A double-tuned solenoidal coil was used to irradiate the same volume of 17O and 1H nuclei, as well as to facilitate direct calibration of the decoupling power. Decoupling efficiency was optimized as was 17O detection sensitivity. Decoupling was most efficient at RF amplitudes below 2.5 kHz (expressed as gamma [17O] x H1), which is within the limits of the acceptable specific absorption rate. Propagation of error analysis demonstrated that 17O detection sensitivity is optimal at a TE equal to the T2 of 17O-depleted water protons. Based on Meiboom's work, a simple theory was formulated for estimating the transverse relaxivity of H2(17)O and the proton signal enhancement produced by decoupling. There was excellent agreement between theory and experiment. Overall, 17O-decoupled spectroscopy and imaging were highly sensitive and accurate in quantifying H2(17)O in vitro.