Localized short‐echo‐time proton MR spectroscopy with full signal‐intensity acquisition

TLDR

The authors developed a short‑echo‑time proton localized spectroscopy sequence by combining a 1D add‑subtract scheme with a doubly slice‑selective spin‑echo sequence. The sequence preserves full magnetization from the VOI, employs an adiabatic pulse for efficient excitation in inhomogeneous RF fields, and uses the add‑subtract localization within a doubly slice‑selective spin‑echo framework. By reducing RF pulses, the method achieves a minimal TE comparable to STEAM, doubles sensitivity, and demonstrates in vivo rat‑brain localization with 2‑μl resolution and SNR above 30. Published in Magn Reson Med 2006; © 2006 Wiley‑Liss, Inc.

Abstract

Abstract We developed a short‐echo‐time (TE) sequence for proton localized spectroscopy by combining a 1D add‐subtract scheme with a doubly slice‐selective spin‐echo (SE) sequence. The sequence preserves the full magnetization available from the selected volume of interest (VOI). By reducing the number of radiofrequency (RF) pulses acting on transverse magnetization, we were able to minimize the TE to the level that is achievable with the stimulated echo acquisition mode (STEAM) technique, and also gained a twofold increase in sensitivity. The use of an adiabatic pulse in the add‐subtract localization improved the efficiency of excitation in spatially inhomogeneous RF fields, which are frequently encountered at high magnetic fields. The localization performance and sensitivity gains of this method, which is termed SPin ECho, full Intensity Acquired Localized (SPECIAL) spectroscopy, were demonstrated in vivo in rat brains. In conjunction with spectroscopic imaging, a 2‐μl spatial resolution was accomplished with a signal‐to‐noise ratio (SNR) above 30, which is usually sufficient for reliable quantification of a large number of metabolites (neurochemical profile). Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.