Efficient H-1 to P-31 Polarization Transfer on a Clinical 3T MR System

P-31 MR spectroscopy (MRS) in the detection of phosphocholine (PC), glycerolphosphocholine (GPC), phosphorylelthanolamine (PE), and glycerolphosphoethanolamine (GPE) compounds has shown clinical potential at 1.5T for several human diseases. The use of H-1 to P-31 polarization transfer can improve the sensitivity using a refocused INEPT method with a potential enhancement of 2.4 (gamma(1H)/gamma(31P)). However, in this method the P-31 signals of PE, PC, GPE, and GPC are strongly attenuated (50% or more) due to J-coupling between P-31 and H-1 that have similar magnitudes for homonuclear J-coupling constants in those metabolites. A method to cancel the homonuclear J-coupling effects in polarization transfer experiments is to apply frequency-selective refocusing pulses, which becomes feasible at 3T due to the increased chemical shift dispersion as compared to 1.5T. In this study, full H-1 to P-31 polarization transfer was realized using chemical shift selective refocusing pulses at 3T. T-1 and T-2 values for H-1 and P-31 spins of PE, PC, GPE, and GPC were measured in the human brain. A more than 2-fold signal-tonoise ratio (SNR) improvement was obtained compared to an optimized direct P-31 MRS method. As shifted RF pulses were used, this method can be applied on a broadband clinical MR system with a single RF system. Magn Reson Med 60: 1298-1305, 2008. (C) 2008 Wiley-Liss, Inc.