In vivo 1 H MR spectroscopy with J-refocusing

• Published in: Magnetic resonance in medicine Vol. 86; no. 6; pp. 2957 - 2965
• Main Authors: Deelchand, Dinesh K, Walls, Jamie D, Marjańska, Małgorzata
• Format: Journal Article
• Language: English
• Published: United States 01-12-2021
• Subjects: Animals; Brain - diagnostic imaging; Glutamine; Magnetic Resonance Spectroscopy; Proton Magnetic Resonance Spectroscopy; Protons; Rats; Rats, Sprague-Dawley; J-coupled metabolites; glutathione; GABA; 9.4 T; brain; glutamine; semi-LASER
• ISSN: 0740-3194; 1522-2594
• DOI: 10.1002/mrm.28936

The goal of this study was to propose a novel localized proton MR spectroscopy (MRS) sequence that reduces signal loss due to J-modulation in the rat brain in vivo.
Sprague-Dawley rats were studied at 9.4 T. A semi-LASER sequence with evenly distributed echo-time (T
) was used, and a 90° J-refocusing pulse was inserted at T
/2. Proton spectra were acquired at two T
s (30 and 68 ms), with and without the J-refocused pulse. Data were processed in MATLAB and quantified with LCModel.
The J-refocused spectrum acquired at T
= 30 ms did not show any signal losses due to J-modulation and had comparable spectral pattern to the one acquired with semi-LASER using the minimum achievable T
. Higher signal amplitudes for glutamine, γ-aminobutyric acid and glutathione led to more reliable quantification precision for these metabolites. The refocused signal intensities at T
= 68 ms were also unaffected by J-modulation but were smaller than the signals at T
= 30 ms mainly due to transverse T
relaxation of metabolites.
The proposed localized MRS sequence will be beneficial in both animal and human MRS studies when using ultra-short T
is not possible while also providing more reliable quantification precision for J-coupled metabolites.