title: TE-averaged two-dimensional proton spectroscopic imaging of glutamate at 3 T.
abstract: Glutamate and glutamine are important neurochemicals in the central nervous system and the neurotoxic properties of excess glutamate have been associated with several neurodegenerative diseases. The TE-Averaged PRESS technique has been shown by our group to detect an unobstructed glutamate signal at 3 T that is resolved from glutamine and NAA at 2.35 ppm. TE-Averaged PRESS therefore provides an unambiguous measurement of glutamate as well as other metabolites such as NAA, choline, creatine, and myo-inositol. In this study, we extend the single voxel TE-Averaged PRESS technique for two-dimensional (2D) spectroscopic imaging (TE-Averaged MRSI) to generate 2D glutamate maps. To facilitate TE-Averaged MRSI within a reasonable time, a fast encoding trajectory was used. This enabled rapid acquisition of TE-Averaged spectral arrays with good spectral bandwidth (977 Hz) and resolution (approximately 2 Hz). MRSI data arrays of 10 x 16 were acquired with 1.8 cm3 spatial resolution over a approximately 110 cm3 volume in a scan time of approximately 21 min. Two-dimensional metabolite maps were obtained with good SNR and clear differentiation in glutamate levels was observed between gray and white matter with significantly higher glutamate in gray matter relative to white matter as anticipated.
authors.affiliation: Center for Molecular and Functional Imaging, University of California San Francisco, 185 Berry Street, Suite #350, San Francisco, CA 94107-1739, USA. rsriniva@mrsc.ucsf.edu
authors.forename: Radhika
authors.initials: R
authors.lastname: Srinivasan
authors.forename: Charles
authors.initials: C
authors.lastname: Cunningham
authors.forename: Albert
authors.initials: A
authors.lastname: Chen
authors.forename: Daniel
authors.initials: D
authors.lastname: Vigneron
authors.forename: Ralph
authors.initials: R
authors.lastname: Hurd
authors.forename: Sarah
authors.initials: S
authors.lastname: Nelson
authors.forename: Daniel
authors.initials: D
authors.lastname: Pelletier
mesh_terms: D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D001921:Brain / Q000033:anatomy & histology*; D001923:Brain Chemistry; D001931:Brain Mapping; D002794:Choline / Q000032:analysis / Q000378:metabolism; D003401:Creatine / Q000378:metabolism; D017352:Echo-Planar Imaging; D005583:Fourier Analysis; D018698:Glutamic Acid / Q000032:analysis*; D005973:Glutamine / Q000378:metabolism; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007294:Inositol / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D012016:Reference Values
chemical_list: D005973:Glutamine; D001224:Aspartic Acid; D018698:Glutamic Acid; D007294:Inositol; C000179:N-acetylaspartate; D003401:Creatine; D002794:Choline