Use of quantitative brain water imaging as concentration reference for J-edited MR spectroscopy of GABA

• Published in: Magnetic resonance imaging Vol. 34; no. 8; pp. 1057 - 1063
• Main Authors: Oeltzschner, Georg, Schnitzler, Alfons, Wickrath, Frithjof, Zöllner, Helge Jörn, Wittsack, Hans-Jörg
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Inc 01.10.2016
• Subjects: 1H-MRS; Body Water - metabolism; Brain - diagnostic imaging; Brain - metabolism; Evaluation Studies as Topic; Female; Gaba MRS; gamma-Aminobutyric Acid - metabolism; Hepatic Encephalopathy - metabolism; Humans; Magnetic Resonance Spectroscopy - methods; Male; MEGA-PRESS; MRS analysis; Quantification; Radiology; Reference Values; Water reference; 1H-MRS; MEGA-PRESS; quantification; MRS analysis; GABA MRS; water reference; Water reference; Quantification; Gaba MRS; H-MRS
• ISSN: 0730-725X; 1873-5894
• DOI: 10.1016/j.mri.2016.04.013

Abstract Purpose To compare two different methods of obtaining the water reference for determination of quantitative water-scaled in vivo concentrations of γ-aminobutyric acid (GABA). Methods Water-scaled GABA estimates for localized J-edited MR spectroscopy experiments can be computed using standard values for tissue-specific water content and relaxation times. Water content and relaxation may, however, be altered in pathology. This work re-analysed data from a recent study in healthy controls and patients with minimal (mHE) or grade I (HE 1) hepatic encephalopathy, a disease associated with slight elevation of brain water content. J-edited MR spectroscopy data were combined with quantitative brain water measures, which provided individual water density references and T 1 relaxation times. Resulting GABA estimates were compared to concentrations obtained using standard tissue-specific water content and relaxation values. Results Occipital GABA concentrations obtained from individual water and T 1 maps were 1.64 ± 0.35 mM in controls, and significantly higher ( P < 0.01) than in mHE (1.15 ± 0.28 mM) and HE 1 patients (1.18 ± 0.09 mM). Results from the tissue-dependent approach (1.58 ± 0.30 mM (controls), 1.10 ± 0.27 mM (mHE) and 1.12 ± 0.12 mM (HE 1)) were slightly lower ( P < 0.05 in each group). Conclusion Water-scaled in vivo GABA estimates can be obtained with individual water density and T 1 relaxation mapping. This approach may be useful for studying GABA levels in pathologies with substantial brain water content or relaxation changes.