DYNAMIC C-13-H-1 NUCLEAR-POLARIZATION OF LIPID METHYLENE RESONANCES APPLIED TO BROAD-BAND PROTON-DECOUPLED IN-VIVO C-13 MR SPECTROSCOPY OF HUMAN BREAST AND CALF TISSUE

Dynamic nuclear polarization of the coupled C-13-H-1 spin system was studied for optimizing the signal-to-noise ratio of in vivo C-13 MR spectra. In particular, the truncated driven and transient nuclear Overhauser effect (NOE) of the proton-decoupled C-13 resonances from methylene carbons in vegetable oil and in human calf tissue was observed. Maximum in vivo NOE enhancements eta = 1.5 and 0.9 were found, respectively. Theoretical fits to the data yield C-13-H-1 cross-relaxation times in the order of 0.6 s. Significant signal enhancement over the whole in vivo C-13 chemical shift range is obtained with minimum expense utilizing the NOE of the dipolar coupled C-13-H-1 spin system in addition to proton-decoupling. NOE-enhanced proton-decoupled in vivo C-13 MR spectra were acquired within 17 min in volunteer examinations from the human breast and the calf. These spectra show well-resolved resonances of carbons in lipids and several other cellular compounds.