Comparison of polarization transfer sequences for enhancement of signals in clinical 31P MRS studies.

Abstract

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.

• Authors: Laura Mancini, Geoffrey S Payne, Martin O Leach
• Journal: Magnetic resonance in medicine (Magn Reson Med) Vol. 50 Issue 3 Pg. 578-88 (Sep 2003) ISSN: 0740-3194 [Print] United States
• PMID: 12939766 (Publication Type: Comparative Study, Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright 2003 Wiley-Liss, Inc.

Chemical References

• Phosphorus
• Choline

Topics

• Chi-Square Distribution
• Choline (metabolism)
• Magnetic Resonance Spectroscopy (methods)
• Models, Theoretical
• Neoplasms (metabolism)
• Phosphorus (metabolism)
• Sensitivity and Specificity
• Signal Processing, Computer-Assisted