Rajakumar Nagarajan¹, Saadallah Ramadan² and M. Albert Thomas¹

¹Department of Radiological Sciences, University of California, Los Angeles, CA 90095, USA. ²Department of Radiology, Brigham and Women Hospital, Boston, MA, 02115, USA.

Abstract

The purpose of the study was to demonstrate the J-coupling connectivity network between the amide, aliphatic, and aromatic proton resonances of metabolites in human brain using two-dimensional (2D) localized correlated spectroscopy (L-COSY). Two  different global water suppression techniques were combined with L-COSY, one before and another after localizing the volume of interest (VOI). Phantom solutions containing several cerebral metabolites at physiological concentrations were evaluated initially for sequence  optimization. Nine healthy volunteers were scanned using a 3T whole body MRI scanner. The VOI for 2D L-COSY was placed in the right occipital white/gray matter region. The 2D cross and diagonal peak volumes were measured for several metabolites such as N-acetyl aspartate (NAA), creatine (Cr), free choline (Ch), glutamate/glutamine (Glx), aspartate (Asp), myo-inositol (mI), GABA, glutathione (GSH), phosphocholine (PCh), phosphoethanolamine (PE), tyrosine (Tyr), lactate (Lac), macromolecules (MM) and  homocarnosine (Car). Using the pre-water suppression technique with L-COSY, the above mentioned metabolites were clearly identifiable and the relative ratios of metabolites were calculated. In addition to detecting multitude of aliphatic resonances in the high field region, we have demonstrated that the amide and aromatic resonances can also be detected using 2D L-COSY by pre water suppression more reliably than the post-water suppression.