title: Imaging of glutamate in the spinal cord using GluCEST.
abstract: Glutamate (Glu) is the most abundant excitatory neurotransmitter in the brain and spinal cord. The concentration of Glu is altered in a range of neurologic disorders that affect the spinal cord including multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS) and spinal cord injury. Currently available magnetic resonance spectroscopy (MRS) methods for measuring Glu are limited to low spatial resolution, which makes it difficult to measure differences in gray and white matter glutamate. Recently, it has been shown that Glu exhibits a concentration dependent chemical exchange saturation transfer (CEST) effect between its amine (-NH2) group protons and bulk water protons (GluCEST). Here, we demonstrate the feasibility of imaging glutamate in the spinal cord at 7T using the GluCEST technique. Results from healthy human volunteers (N=7) showed a significantly higher (p<0.001) GluCESTasym from gray matter (6.6±0.3%) compared to white matter (4.8±0.4%). Potential overlap of CEST signals from other spinal cord metabolites with the observed GluCESTasym is discussed. This noninvasive approach potentially opens the way to image Glu in vivo in the spinal cord and to monitor its alteration in many disease conditions.
authors.affiliation: Center for Magnetic Resonance and Optical Imaging, Department of Radiology, University of Pennsylvania, Philadelphia, PA, USA. fkogan@seas.upenn.edu
authors.forename: Feliks
authors.initials: F
authors.lastname: Kogan
authors.forename: Anup
authors.initials: A
authors.lastname: Singh
authors.forename: Catherine
authors.initials: C
authors.lastname: Debrosse
authors.forename: Mohammad
authors.initials: M
authors.lastname: Haris
authors.forename: Kejia
authors.initials: K
authors.lastname: Cai
authors.forename: Ravi Prakash
authors.initials: RP
authors.lastname: Nanga
authors.forename: Mark
authors.initials: M
authors.lastname: Elliott
authors.forename: Hari
authors.initials: H
authors.lastname: Hariharan
authors.forename: Ravinder
authors.initials: R
authors.lastname: Reddy
mesh_terms: D000328:Adult; D005260:Female; D018698:Glutamic Acid / Q000032:analysis*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D013116:Spinal Cord / Q000737:chemistry* / Q000378:metabolism*; D055815:Young Adult
chemical_list: D018698:Glutamic Acid