Use of quantitative brain water imaging as concentration reference for J-edited MR spectroscopy of GABA.
To compare two different methods of obtaining the water reference for determination of quantitative water-scaled in vivo concentration estimates of γ-aminobutyric acid (GABA).



Water-scaled GABA estimates from localized J-difference 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-analyzed 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-difference edited MR spectroscopy data were combined with quantitative brain water measures, which provided individual water density references and T1 relaxation times. Resulting GABA estimates were compared to concentration values obtained using standard tissue-specific water content and relaxation values.



Occipital GABA concentration values obtained from individual water and T1 maps were 1.64±0.35mM in controls, and significantly higher (P<0.01) than in mHE (1.15±0.28mM) and HE 1 patients (1.18±0.09mM). Results from the tissue-dependent approach (1.58±0.30mM (controls), 1.10±0.27mM (mHE) and 1.12±0.12mM (HE 1)) were slightly lower (P<0.05 in each group).



Water-scaled in vivo GABA estimates can be obtained with individual water density and T1 relaxation mapping. This approach may be useful for studying GABA levels in pathologies with substantial brain water content or relaxation changes.
Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich-Heine-University Düsseldorf, D-40225, Düsseldorf, Germany; Department of Diagnostic and Interventional Radiology, University Dusseldorf, Medical Faculty, D-40225, Düsseldorf, Germany; Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, United States; F.M. Kirby Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, United States. Electronic address: oeltzschner@gmail.com.
Georg
G
Oeltzschner
Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich-Heine-University Düsseldorf, D-40225, Düsseldorf, Germany.
Alfons
A
Schnitzler
Department of Diagnostic and Interventional Radiology, University Dusseldorf, Medical Faculty, D-40225, Düsseldorf, Germany.
Frithjof
F
Wickrath
Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich-Heine-University Düsseldorf, D-40225, Düsseldorf, Germany; Department of Diagnostic and Interventional Radiology, University Dusseldorf, Medical Faculty, D-40225, Düsseldorf, Germany.
Helge Jörn
HJ
Zöllner
Department of Diagnostic and Interventional Radiology, University Dusseldorf, Medical Faculty, D-40225, Düsseldorf, Germany.
Hans-Jörg
HJ
Wittsack
D001834:Body Water / Q000378:metabolism*; D001921:Brain / Q000000981:diagnostic imaging* / Q000378:metabolism*; D005069:Evaluation Studies as Topic; D005260:Female; D006501:Hepatic Encephalopathy / Q000378:metabolism*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D012016:Reference Values; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D005680:gamma-Aminobutyric Acid
(1)H-MRS; Gaba MRS; MEGA-PRESS; MRS analysis; Quantification; Water reference