title: Human cardiac 31P magnetic resonance spectroscopy at 7 Tesla.
abstract: OBJECTIVE
  Phosphorus magnetic resonance spectroscopy ((31)P-MRS) affords unique insight into cardiac energetics but has a low intrinsic signal-to-noise ratio (SNR) in humans. Theory predicts an increased (31)P-MRS SNR at 7T, offering exciting possibilities to better investigate cardiac metabolism. We therefore compare the performance of human cardiac (31)P-MRS at 7T to 3T, and measure T1s for (31)P metabolites at 7T.
  
  
  METHODS
  Matched (31)P-MRS data were acquired at 3T and 7T, on nine normal volunteers. A novel Look-Locker CSI acquisition and fitting approach was used to measure T1s on six normal volunteers.
  
  
  RESULTS
  T1s in the heart at 7T were: phosphocreatine (PCr) 3.05 ± 0.41s, γ-ATP 1.82 ± 0.09s, α-ATP 1.39 ± 0.09s, β-ATP 1.02 ± 0.17s and 2,3-DPG (2,3-diphosphoglycerate) 3.05 ± 0.41s (N = 6). In the field comparison (N = 9), PCr SNR increased 2.8× at 7T relative to 3T, the Cramer-Ráo uncertainty (CRLB) in PCr concentration decreased 2.4×, the mean CRLB in PCr/ATP decreased 2.7× and the PCr/ATP SD decreased 2×.
  
  
  CONCLUSIONS
  Cardiac (31)P-MRS at 7T has higher SNR and the spectra can be quantified more precisely than at 3T. Cardiac (31)P T1s are shorter at 7T than at 3T. We predict that 7T will become the field strength of choice for cardiac (31)P-MRS.
authors.affiliation: Oxford Centre for Clinical Magnetic Resonance Research (OCMR), University of Oxford, Level 0, John Radcliffe Hospital, Oxford, United Kingdom.
authors.forename: Christopher T
authors.initials: CT
authors.lastname: Rodgers
authors.forename: William T
authors.initials: WT
authors.lastname: Clarke
authors.forename: Carl
authors.initials: C
authors.lastname: Snyder
authors.forename: J Thomas
authors.initials: JT
authors.lastname: Vaughan
authors.forename: Stefan
authors.initials: S
authors.lastname: Neubauer
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Robson
mesh_terms: D000328:Adult; D000465:Algorithms; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D057054:Molecular Imaging / Q000379:methods; D009206:Myocardium / Q000378:metabolism*; D017553:Phosphorus Compounds / Q000378:metabolism*; D010759:Phosphorus Isotopes / Q000493:pharmacokinetics; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D023822:Tissue Engineering; D055815:Young Adult
chemical_list: D017553:Phosphorus Compounds; D010759:Phosphorus Isotopes; D019275:Radiopharmaceuticals
keywords: 31P magnetic resonance spectroscopy; 7 Tesla; T1; cardiac; field strength; phosphorus