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Comparison of polarization transfer sequences for enhancement of signals in clinical 31 P MRS studies
Author(s) -
Mancini Laura,
Payne Geoffrey S.,
Leach Martin O.
Publication year - 2003
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.10551
Subject(s) - homonuclear molecule , heteronuclear molecule , nuclear magnetic resonance , chemistry , phosphomonoesters , heteronuclear single quantum coherence spectroscopy , coherence (philosophical gambling strategy) , dept , polarization (electrochemistry) , analytical chemistry (journal) , physics , nuclear magnetic resonance spectroscopy , molecule , stereochemistry , organic chemistry , quantum mechanics , chromatography , enzyme , inorganic phosphate
Several 31 P MRS studies in tumors in vivo have shown that levels of phosphocholine (PC) and other phosphomonoesters (PME) and phosphodiesters (PDE) are useful prognostic or early‐response indicators. To improve sensitivity for such measurements, four polarization transfer (PT) sequences (insensitive nuclei enhanced by PT (INEPT), distortionless enhancement by PT (DEPT), reverse‐INEPT, and heteronuclear single‐quantum coherence (HSQC)) were assessed theoretically and experimentally. The presence of homonuclear ( 1 H‐ 1 H) and heteronuclear ( 31 P‐ 1 H) couplings of similar magnitude makes theoretical analysis very sensitive to precise model parameters, especially for the 1 H‐detected sequences. The 1 H‐ 1 H coupling causes the splitting of 1 H peaks, and hence reduces the proton spectral resolution. This effect and a 50% signal loss from gradient‐enhanced water suppression negate the usual advantages of 1 H‐detection. Among the PT methods, INEPT gave the higher signal enhancement. However, T 2 losses during the long echo times (TEs) required by the weak coupling limited the resulting signals from PC. Magn Reson Med 50:578–588, 2003. © 2003 Wiley‐Liss, Inc.