O-decoupled proton MR spectroscopy and imaging were im-T 2 -weighted proton NMR methods have been used to plemented at 2 T. Their sensitivity and accuracy in vitro were quantify relative H 2 17 O concentrations in tissues in vivo examined using semisolid tissue phantoms doped with H 2 17 O. A (3, 17-21). In these methods, errors in the calculated H 2 17 O double-tuned solenoidal coil was used to irradiate the same volume concentration can arise from spatial misregistration and 17 Oof 17 O and 1 H nuclei, as well as to facilitate direct calibration of independent changes in tissue T 2 . Ronen and Navon have the decoupling power. Decoupling efficiency was optimized as was introduced a novel method for realizing the full potential of 17 O detection sensitivity. Decoupling was most efficient at RF amindirect 17 O detection by T 2 -weighted proton NMR (22).
plitudes below 2.5 kHz (expressed as g[ 17 O] 1 H 1 ), which is within Their method uses radiofrequency irradiation at the 17 O resothe limits of the acceptable specific absorption rate. Propagation of nance frequency, applied during evolution of the proton spin error analysis demonstrated that 17 O detection sensitivity is optiecho, to decouple [ 17 O-1 H] spin-spin coupling and thereby mal at a TE equal to the T 2 of 17 O-depleted water protons. Based on Meiboom's work, a simple theory was formulated for estimating prolong proton T 2 relaxation times. Ronen and Navon have the transverse relaxivity of H 2 17 O and the proton signal enhanceshown that 17 O-decoupled NMR can be used to detect H 2 17 O ment produced by decoupling. There was excellent agreement bein aqueous phantoms at 8.4 T. To our knowledge, the decoutween theory and experiment. Overall, 17 O-decoupled spectroscopy pling method has not been critically evaluated with respect to and imaging were highly sensitive and accurate in quantifying accuracy in quantifying H 2 17 O, optimization of experimental H 2 17 O in vitro. α§ 1997 Academic Press parameters, or sensitivity for H 2 17 O detection. In this article we formulate a theory of 17 O relaxivity and describe the implementation of 17 O-decoupled MR spectroscopy and im-* To whom correspondence should be addressed.