Program Information
Simultaneous Detection of Glutamate, Glutamine, and GABA with An Optimized PRESS Sequence at 9.4 T
B Dobberthien1*, AG Tessier1,2 , A Yahya1,2 , (1) Department of Oncology, University of Alberta, Edmonton, AB, (2) Department of Medical Physics, Cross Cancer Institute, Edmonton, AB
Presentations
SU-K-702-8 (Sunday, July 30, 2017) 4:00 PM - 6:00 PM Room: 702
Purpose: To optimize the commonly employed Magnetic Resonance Spectroscopy (MRS) Point RESolved Spectroscopy (PRESS) pulse sequence for improved simultaneous quantification of glutamate (Glu), glutamine (Gln), and γ-aminobutyric acid (GABA) in vivo in rat brain at 9.4 T. The three metabolites are relevant to the study of cancer.
Methods: The spectral response of Glu (≈2.35 ppm), Gln (≈2.45 ppm), GABA (≈2.28 ppm), and N-acetylaspartate (NAA; ≈2.49 ppm) protons to varying echo times (TE₁ and TE₂) of a PRESS sequence were investigated numerically. An objective function was created by subtracting the normalized peak area of NAA from that of Gln, which overlaps the most with NAA. A contour plot was created based on this function, with TE₁ and TE₂ varying in steps of 2 ms. The {TE₁, TE₂} combination that maximized the objective function and retained sufficient peak areas for Glu and GABA was considered optimal. This timing set was verified on phantom solutions and in vivo on five Sprague Dawley rat brains. In-vivo spectra were analyzed with LCModel.
Results: The optimal {TE₁, TE₂} combination was determined to be {106 ms, 16 ms}, which yielded an objective function value of 0.65 and simulated peak areas of -0.02, 0.42, 0.54, and 0.57 for NAA, Gln, Glu, and GABA, respectively, relative to the corresponding {2 ms, 2 ms} values. For individual phantom solutions, the optimal TE gave peak areas of ≤0.05, 0.44, 0.59, and 0.70, relative to the corresponding short-TE values, respectively. The in-vivo spectra had average T₂-corrected concentrations of 3.19 mM, 10.76 mM, and 2.07 mM with Cramér-Rao Lower Bound (CRLB) values of ≤17%, ≤6%, and ≤19% for Gln, Glu, and GABA, respectively.
Conclusion: A PRESS {TE₁, TE₂} combination of {106 ms, 16 ms} is suitable for simultaneous quantification of Glu, Gln, and GABA in vivo in rat brain at 9.4 T.
Funding Support, Disclosures, and Conflict of Interest: Research was funded by the Natural Sciences and Engineering Research Council of Canada. We do not have any conflicts of interest.
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