17O-decoupled 1H detection using a double-tuned coil.

ABSTRACT

17O-decoupled proton MR spectroscopy imaging with a double-tuned radiofrequency (RF) coil at 2 T was used to detect and quantify H2 17O in tissue containing various concentrations of 17O-enriched water in 5% gelatin. The pulse sequence used in these experiments consisted of a conventional proton spin-echo sequence with RF irradiation at the 17O resonance frequency applied between the proton 90 degrees pulse and the signal acquisition window. The double-tuned coil provided several advantages over systems using separate RF coils for 17O decoupling and proton excitation/detection, including ensuring that the same (or similar) sample volumes are excited and decoupled and permitting accurate calibration of the 17O decoupling pulse amplitude. The efficiency of 17O decoupling as a function of decoupling RF amplitude, decoupling duration, and decoupling resonance offset was investigated. Finally, the specific absorption rate of the 17O decoupled pulse sequence was investigated and found to lie within federal guidelines at 1.5 T.