Increase in SNR for 31P MR spectroscopy by combining polarization transfer with a direct detection sequence



The sensitivity of 31P MRS can be increased using higher magnetic fields, but also by using 1H to 31P polarization transfer techniques where the sensitivity is determined by the polarization of the proton spins and thus the signal-to-noise per unit time is unaffected by the slow T1 relaxation properties of the 31P spins. This implies that 31P spins can be manipulated during the T1 relaxation of the 1H spins without affecting the signal-to-noise of the 1H to 31P polarization transferred spins. It is shown here that by combining 1H to 31P polarization transfer with a direct 31P detection sequence in one repetition time, one can gain more signal-to-noise per unit of time as compared to a polarization transfer sequence alone. Proof of principle was demonstrated by phantom measurements and additionally the method was applied to the human calf muscle and to the human breast in vivo at 7T. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.