Efficient 1H to 31P polarization transfer on a clinical 3T MR system

• Published in: Magnetic resonance in medicine 2008-12, Vol.60 (6), p.1298-1305
• Main Authors: Klomp, D.W.J., Wijnen, J.P., Scheenen, T.W.J., Heerschap, A.
• Format: Article
• Language: English
• Subjects: 31P MRS; Algorithms; Brain - anatomy & histology; Brain - metabolism; Humans; Magnetic Resonance Spectroscopy - methods; phosphocholine; phosphoethanolamine; Phosphorus Compounds - analysis; Phosphorus Radioisotopes; polarization transfer; Protons; Reproducibility of Results; Sensitivity and Specificity; Spin Labels
• ISSN: 0740-3194; 1522-2594
• DOI: 10.1002/mrm.21733

31P 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 1H to 31P polarization transfer can improve the sensitivity using a refocused INEPT method with a potential enhancement of 2.4 (γ1H/γ31P). However, in this method the 31P signals of PE, PC, GPE, and GPC are strongly attenuated (50% or more) due to J‐coupling between 31P and 1H 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 1H to 31P polarization transfer was realized using chemical shift selective refocusing pulses at 3T. T1 and T2 values for 1H and 31P spins of PE, PC, GPE, and GPC were measured in the human brain. A more than 2‐fold signal‐to‐noise ratio (SNR) improvement was obtained compared to an optimized direct 31P 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. © 2008 Wiley‐Liss, Inc.