Poster - 04: Resolving the Glutamine Resonance with an Optimized Magnetic Resonance Spectroscopy PRESS Sequence at 9.4T

Abstract

Purpose: To optimize the timings of the magnetic resonance spectroscopy technique, Point RESolved Spectroscopy (PRESS), to resolve glutamine (Gln; ∼2.45ppm) in vivo at 9.4T. The Gln resonance is contaminated by N-acetylaspartate (NAA; ∼2.49ppm) and to a lesser extent by glutathione (GSH; ∼2.51ppm). Methods: Signals of glutamate (Glu; ∼2.35ppm), Gln, and NAA at 9.4T in response to TE (echo time) values of a PRESS sequence were investigated numerically, and the {TE1, TE2} combination that best resolved Gln while retaining Glu was considered optimal. The timings were verified on phantom solutions and in vivo on four Sprague Dawley rat brains. In-vivo spectra were analyzed with LCmodel. Results: An optimal {TE1, TE2} combination was determined to be {106ms, 16ms}, which resulted in simulated peak areas for Glu, Gln, and NAA, of 54%, 42%, and −2%, respectively, of the corresponding shortest {2ms, 2ms} values. Experimentally, the Gln yield with the optimal TE values was found to be ∼54% of that obtained with a short-TE of {TE1, TE2} = {12ms, 9ms}. The yield changed by <10% with the addition of NAA and GSH. The rat brain spectra showed well resolved peaks for Glu and Gln at ∼2.35ppm and ∼2.45ppm, respectively. LCModel Cramer-Rao Lower Bound values for all rats were <8% and <20% for Glu and Gln, respectively. Conclusions: A PRESS sequence with {TE1, TE2} = {106ms, 16ms} is suitable for resolving Gln in vivo at 9.4T.