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.