title: Band inversion amplifies31P-31P nuclear overhauser effects: Relaxation mechanism and dynamic behavior of ATP in the human brain by31P MRS at 7 T.
abstract: To develop an improved method to measure the31P nuclear Overhauser effect (NOE) for evaluation of adenosine triphosphate (ATP) dynamics in terms of correlation time (τc), and contribution of dipole-dipole (DD) and chemical shift anisotropy (CSA) mechanisms to T1relaxation of ATP in human brain.
  
  
  
  The NOE of ATP in human brain was evaluated by monitoring changes in magnetization in the β-ATP signal following a band inversion of all downfield31P resonances. The magnetization changes observed were analyzed using the Bloch-McConnell-Solomon formulation to evaluate the relaxation and motion dynamic parameters that describe interactions of ATP with cellular solids in human brain tissue.
  
  
  
  The maximal transient NOE, observed as a reduction in the β-ATP signal, was 24 ± 2% upon band inversion of γ- and α-ATP, which is 2-3-fold higher than achievable by frequency-selective inversion of either γ- or α-ATP. The rate of31P-31P cross relaxation (0.21 ± 0.02 s-1) led to a τcvalue of (9.1 ± 0.8) × 10-8s for ATP in human brain. The T1relaxation of β-ATP is dominated by CSA over the DD mechanism (60%: 40%).
  
  
  
  The band inversion method proved effective in amplifying31P NOE, and thus facilitating ATP τcand relaxation measurements. This technique renders ATP a potentially useful reporter molecule for cellular environments. Magn Reson Med 77:1409-1418, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
authors.affiliation: Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, 75390.|Department of Radiology, University of Texas Southwestern Medical Center, Dallas, TX, 75390.
authors.forename: Jimin
authors.initials: J
authors.lastname: Ren
authors.affiliation: Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, 75390.|Department of Radiology, University of Texas Southwestern Medical Center, Dallas, TX, 75390.|Department of Chemistry, University of Texas at Dallas, Richardson, TX, 75080.
authors.forename: A Dean
authors.initials: AD
authors.lastname: Sherry
authors.affiliation: Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, 75390.|Department of Radiology, University of Texas Southwestern Medical Center, Dallas, TX, 75390.|Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, 75390.|VA North Texas Health Care System, Dallas, TX, 75216.
authors.forename: Craig R
authors.initials: CR
authors.lastname: Malloy
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000328:Adult; D000465:Algorithms; D001921:Brain / Q000378:metabolism*; D005260:Female; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D008657:Metabolic Clearance Rate; D010759:Phosphorus Isotopes / Q000493:pharmacokinetics*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted
chemical_list: D010759:Phosphorus Isotopes; D019275:Radiopharmaceuticals; D000255:Adenosine Triphosphate
keywords: ATP; NOE; T1 relaxation; cross relaxation; dynamics; inversion transfer; magnetization transfer