A method for rapid evaluation of saturation factors in in vivo surface coil NMR spectroscopy using B1-insensitive pulse cycles

For a rapid determination of saturation factors in surface coil NMR spectroscopy, the recently published (90 degrees-tau-180 degrees-tau-90 degrees-tau-) SUFIR sequence was modified with adiabatic pulse cycles. Signals were acquired after each of the two 90 degrees pulses and they were stored in different memory blocks. The deleterious offset-dependent saturation effects inherent in adiabatic 90 degrees excitation pulses were minimized by suitable combinations of adiabatic pulses that sweep from either side of the spectrum onto resonance, and by setting the carrier frequency in the middle of the spectrum. The practical use of the proposed method is illustrated with the determination of 31P NMR saturation factors in human calf muscle.