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

✍ Scribed by Ricardo Otazo; Bryon Mueller; Kamil Ugurbil; Lawrence Wald; Stefan Posse

• Publisher: John Wiley and Sons
• Year: 2006
• Tongue: English
• Weight: 831 KB
• Volume: 56
• Category: Article
• ISSN: 0740-3194
• DOI: 10.1002/mrm.21067

✦ Synopsis

Abstract

This study characterizes gains in sensitivity and spectral resolution of proton echo‐planar spectroscopic imaging (PEPSI) with increasing magnetic field strength (B~0~). 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 B~0~. 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 B~0~ in central brain regions. For the PA coil, the SNR–B~0~ 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 B~0~, resulting in improved spectral resolution. These studies using PEPSI demonstrated linear gains in SNR with respect to B~0~, consistent with theoretical expectations, and a decrease in ppm LW with increasing B~0~. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.