Surface-coil polarization transfer for monitoring tissue metabolism in vivo.

Polarization transfer methods can substantially enhance NMR signals from nuclei of low gamma, which are J-coupled to nuclei of high gamma, but to date have had limited application for in vivo (31)P MRS studies. They require both accurate flip angles and good localization in order to achieve their potential. Described here is an implementation of the insensitive nuclei enhanced by polarization transfer (INEPT) polarization transfer method using segmented adiabatic BIR4 RF pulses. Localization uses ISIS, applied to the coupled (1)H spins. Detailed analysis is performed to evaluate the specific absorption rate power deposition when using surface coils. Polarization transfer, localization capability, and use with surface coils are demonstrated using suitable test objects. Finally, in vivo data are presented from the liver of a normal volunteer in which the signals from the phosphodiester peaks are substantially enhanced.