title: Phosphatidylcholine contributes to in vivo (31)P MRS signal from the human liver.
abstract: OBJECTIVE
  To demonstrate the overlap of the hepatic and bile phosphorus ((31)P) magnetic resonance (MR) spectra and provide evidence of phosphatidylcholine (PtdC) contribution to the in vivo hepatic (31)P MRS phosphodiester (PDE) signal, suggested in previous reports to be phosphoenolpyruvate (PEP).
  
  
  METHODS
  Phantom measurements to assess the chemical shifts of PEP and PtdC signals were performed at 7 T. A retrospective analysis of hepatic 3D (31)P MR spectroscopic imaging (MRSI) data from 18 and five volunteers at 3 T and 7 T, respectively, was performed. Axial images were inspected for the presence of gallbladder, and PDE signals in representative spectra were quantified.
  
  
  RESULTS
  Phantom experiments demonstrated the strong pH-dependence of the PEP chemical shift and proved the overlap of PtdC and PEP (~2 ppm relative to phosphocreatine) at hepatic pH. Gallbladder was covered in seven of 23 in vivo 3D-MRSI datasets. The PDE(gall)/γ-ATP(liver) ratio was 4.8-fold higher (p = 0.001) in the gallbladder (PDE(gall)/γ-ATP(liver) = 3.61 ± 0.79) than in the liver (PDE(liver)/γ-ATP(liver) = 0.75 ± 0.15). In vivo 7 T (31)P MRSI allowed good separation of PDE components. The gallbladder is a strong source of contamination in adjacent (31)P MR hepatic spectra due to biliary phosphatidylcholine.
  
  
  CONCLUSIONS
  In vivo (31)P MR hepatic signal at 2.06 ppm may represent both phosphatidylcholine and phosphoenolpyruvate, with a higher phosphatidylcholine contribution due to its higher concentration.
  
  
  CONCLUSIONS
  • In vivo (31)P MRS from the gallbladder shows a dominant biliary phosphatidylcholine signal at 2.06 ppm. • Intrahepatic (31)P MRS signal at 2.06 ppm may represent both intrahepatic phosphatidylcholine and phosphoenolpyruvate. • In vivo (31)P MRS has the potential to monitor hepatic phosphatidylcholine.
authors.affiliation: MR Centre of Excellence, Department of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna, Vienna, Austria.
authors.forename: Marek
authors.initials: M
authors.lastname: Chmelík
authors.forename: Ladislav
authors.initials: L
authors.lastname: Valkovič
authors.forename: Peter
authors.initials: P
authors.lastname: Wolf
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Bogner
authors.forename: Martin
authors.initials: M
authors.lastname: Gajdošík
authors.forename: Emina
authors.initials: E
authors.lastname: Halilbasic
authors.forename: Stephan
authors.initials: S
authors.lastname: Gruber
authors.forename: Michael
authors.initials: M
authors.lastname: Trauner
authors.forename: Michael
authors.initials: M
authors.lastname: Krebs
authors.forename: Siegfried
authors.initials: S
authors.lastname: Trattnig
authors.forename: Martin
authors.initials: M
authors.lastname: Krššák
mesh_terms: D000328:Adult; D001646:Bile / Q000378:metabolism*; D005704:Gallbladder / Q000378:metabolism*; D064368:Healthy Volunteers; D006801:Humans; D008099:Liver / Q000378:metabolism*; D008279:Magnetic Resonance Imaging / Q000379:methods; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D019047:Phantoms, Imaging; D010713:Phosphatidylcholines / Q000378:metabolism*; D010728:Phosphoenolpyruvate / Q000378:metabolism; D010759:Phosphorus Isotopes / Q000493:pharmacokinetics; D011446:Prospective Studies; D012189:Retrospective Studies
chemical_list: D010713:Phosphatidylcholines; D010759:Phosphorus Isotopes; D010728:Phosphoenolpyruvate