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

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.