Signal-to-noise ratio and spectral linewidth improvements between 1.5 and 7 tesla in proton echo-planar spectroscopic imaging

Ricardo Otazo, Bryon Mueller, Kamil Ugurbil, Lawrence Wald, Stefan Posse

Research output: Contribution to journalArticlepeer-review

94 Scopus citations

Abstract

This study characterizes gains in sensitivity and spectral resolution of proton echo-planar spectroscopic imaging (PEPSI) with increasing magnetic field strength (B0). Signal-to-noise ratio (SNR) per unit volume and unit time, and intrinsic linewidth (LW) of N-acetyl-aspartate (NAA), creatine (Cr), and choline (Cho) were measured with PEPSI at 1.5, 3, 4, and 7 Tesla on scanners that shared a similar software and hardware platform, using circularly polarized (CP) and eight-channel phased-array (PA) head coils. Data were corrected for relaxation effects and processed with a time-domain matched filter (MF) adapted to each B0. The SNR and LW measured with PEPSI were very similar to those measured with conventional point-resolved spectroscopy (PRESS) SI. Measurements with the CP coil demonstrated a nearly linear SNR gain with respect to B0 in central brain regions. For the PA coil, the SNR-B0 relationship was less than linear, but there was a substantial SNR increase in comparison to the CP coil. The LW in units of ppm decreased with B0, resulting in improved spectral resolution. These studies using PEPSI demonstrated linear gains in SNR with respect to B0, consistent with theoretical expectations, and a decrease in ppm LW with increasing B0.

Original languageEnglish (US)
Pages (from-to)1200-1210
Number of pages11
JournalMagnetic resonance in medicine
Volume56
Issue number6
DOIs
StatePublished - Dec 2006

Keywords

  • High field
  • Linewidth
  • Magnetic resonance
  • Signal-to-noise ratio
  • Spectroscopic imaging

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