Indirect 13C tomography and volume-selective spectroscopy via proton NMR. I. Spectroscopic techniques

The sensitivity of ¹³C spectroscopy can be considerably enhanced by selectively detecting the hydrogen nuclei bound to the '3C nuclei of interest. The maximum signal enhancement is theoretically a factor of 64 times the number of protons coupled to a ¹³C nucleus. Three different pulse sequences which permit the image-guided volume-selective single-scan editing of protons bound to ¹³C are reported. The methods are partially designed to be insensitive to the pulse phases and amplitudes and as far as possible to coherent motions. The procedures are based on the same principles as the homonuclear versions previously reported. The lines are edited by multiple-quantum, split-pathway, or cyclic polarization transfer filtering. The sequences have been implemented on 4.7 and 2 T NMR tomographs. Tests have been carried out with phantom samples as well as with volunteers.