title: Applications of multi-nuclear magnetic resonance spectroscopy at 7T.
abstract: OBJECTIVE
  To discuss the advantages of ultra-high field (7T) for (1)H and (13)C magnetic resonance spectroscopy (MRS) studies of metabolism.
  
  
  METHODS
  Measurements of brain metabolites were made at both 3 and 7T using (1)H MRS. Measurements of glycogen and lipids in muscle were measured using (13)C and (1)H MRS respectively.
  
  
  RESULTS
  In the brain, increased signal-to-noise ratio (SNR) and dispersion allows spectral separation of the amino-acids glutamate, glutamine and γ-aminobutyric acid (GABA), without the need for sophisticated editing sequences. Improved quantification of these metabolites is demonstrated at 7T relative to 3T. SNR was 36% higher, and measurement repeatability (% coefficients of variation) was 4%, 10% and 10% at 7T, vs 8%, 29% and 21% at 3T for glutamate, glutamine and GABA respectively. Measurements at 7T were used to compare metabolite levels in the anterior cingulate cortex (ACC) and insula. Creatine and glutamate levels were found to be significantly higher in the insula compared to the ACC (P < 0.05). In muscle, the increased SNR and spectral resolution at 7T enables interleaved studies of glycogen ((13)C) and intra-myocellular lipid (IMCL) and extra-myocellular lipid (EMCL) ((1)H) following exercise and re-feeding. Glycogen levels were significantly decreased following exercise (-28% at 50% VO(2) max; -58% at 75% VO(2) max). Interestingly, levels of glycogen in the hamstrings followed those in the quadriceps, despite reduce exercise loading. No changes in IMCL and EMCL were found in the study.
  
  
  CONCLUSIONS
  The demonstrated improvements in brain and muscle MRS measurements at 7T will increase the potential for use in investigating human metabolism and changes due to pathologies.
authors.affiliation: Mary C Stephenson, Susan T Francis, Peter G Morris, The Sir Peter Mansfield Magnetic Resonance Centre, School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, United Kingdom.
authors.forename: Mary C
authors.initials: MC
authors.lastname: Stephenson
authors.forename: Frances
authors.initials: F
authors.lastname: Gunner
authors.forename: Antonio
authors.initials: A
authors.lastname: Napolitano
authors.forename: Paul L
authors.initials: PL
authors.lastname: Greenhaff
authors.forename: Ian A
authors.initials: IA
authors.lastname: Macdonald
authors.forename: Nadeem
authors.initials: N
authors.lastname: Saeed
authors.forename: William
authors.initials: W
authors.lastname: Vennart
authors.forename: Susan T
authors.initials: ST
authors.lastname: Francis
authors.forename: Peter G
authors.initials: PG
authors.lastname: Morris