title: Absolute Quantification of Human Liver Phosphorus-Containing Metabolites In Vivo Using an Inhomogeneous Spoiling Magnetic Field Gradient.
abstract: OBJECTIVE
  Absolute concentrations of high-energy phosphorus (31P) metabolites in liver provide more important insight into physiologic status of liver disease compared to resonance integral ratios. A simple method for measuring absolute concentrations of 31P metabolites in human liver is described. The approach uses surface spoiling inhomogeneous magnetic field gradient to select signal from liver tissue. The technique avoids issues caused by respiratory motion, chemical shift dispersion associated with linear magnetic field gradients, and increased tissue heat deposition due to radiofrequency absorption, especially at high field strength.
  
  
  METHODS
  A method to localize signal from liver was demonstrated using superficial and highly non-uniform magnetic field gradients, which eliminate signal(s) from surface tissue(s) located between the liver and RF coil. A double standard method was implemented to determine absolute 31P metabolite concentrations in vivo. 8 healthy individuals were examined in a 3 T MR scanner.
  
  
  RESULTS
  Concentrations of metabolites measured in eight healthy individuals are: γ-adenosine triphosphate (ATP) = 2.44 ± 0.21 (mean ± sd) mmol/l of wet tissue volume, α-ATP = 3.2 ± 0.63 mmol/l, β-ATP = 2.98 ± 0.45 mmol/l, inorganic phosphates (Pi) = 1.87 ± 0.25 mmol/l, phosphodiesters (PDE) = 10.62 ± 2.20 mmol/l and phosphomonoesters (PME) = 2.12 ± 0.51 mmol/l. All are in good agreement with literature values.
  
  
  CONCLUSIONS
  The technique offers robust and fast means to localize signal from liver tissue, allows absolute metabolite concentration determination, and avoids problems associated with constant field gradient (linear field variation) localization methods.
authors.affiliation: Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, Missouri, United States of America.
authors.forename: Adil
authors.initials: A
authors.lastname: Bashir
authors.affiliation: Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, Missouri, United States of America.
authors.forename: Robert
authors.initials: R
authors.lastname: Gropler
authors.affiliation: Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, Missouri, United States of America.|Department of Chemistry, Washington University, St. Louis, Missouri, United States of America.
authors.forename: Joseph
authors.initials: J
authors.lastname: Ackerman
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000328:Adult; D006801:Humans; D008099:Liver / Q000378:metabolism*; D008107:Liver Diseases / Q000175:diagnosis* / Q000378:metabolism; D060526:Magnetic Fields; D008875:Middle Aged; D010710:Phosphates / Q000378:metabolism*; D010758:Phosphorus / Q000378:metabolism*; D010759:Phosphorus Isotopes / Q000378:metabolism*; D055815:Young Adult
chemical_list: D010710:Phosphates; D010759:Phosphorus Isotopes; D010758:Phosphorus; D000255:Adenosine Triphosphate