title: Application of localized ³¹P MRS saturation transfer at 7 T for measurement of ATP metabolism in the liver: reproducibility and initial clinical application in patients with non-alcoholic fatty liver disease.
abstract: OBJECTIVE
  Saturation transfer (ST) phosphorus MR spectroscopy ((31)P MRS) enables in vivo insight into energy metabolism and thus could identify liver conditions currently diagnosed only by biopsy. This study assesses the reproducibility of the localized (31)P MRS ST in liver at 7 T and tests its potential for noninvasive differentiation of non-alcoholic fatty liver (NAFL) and steatohepatitis (NASH).
  
  
  METHODS
  After the ethics committee approval, reproducibility of the localized (31)P MRS ST at 7 T and the biological variation of acquired hepato-metabolic parameters were assessed in healthy volunteers. Subsequently, 16 suspected NAFL/NASH patients underwent MRS measurements and diagnostic liver biopsy. The Pi-to-ATP exchange parameters were compared between the groups by a Mann-Whitney U test and related to the liver fat content estimated by a single-voxel proton ((1)H) MRS, measured at 3 T.
  
  
  RESULTS
  The mean exchange rate constant (k) in healthy volunteers was 0.31 ± 0.03 s(-1) with a coefficient of variation of 9.0 %. Significantly lower exchange rates (p < 0.01) were found in NASH patients (k = 0.17 ± 0.04 s(-1)) when compared to healthy volunteers, and NAFL patients (k = 0.30 ± 0.05 s(-1)). Significant correlation was found between the k value and the liver fat content (r = 0.824, p < 0.01).
  
  
  CONCLUSIONS
  Our data suggest that the (31)P MRS ST technique provides a tool for gaining insight into hepatic ATP metabolism and could contribute to the differentiation of NAFL and NASH.
  
  
  CONCLUSIONS
  • 1D localized (31) P MRS saturation transfer in the liver is reproducible at 7 T • NASH patients have decreased hepatic Pi-to-ATP exchange rate • In this study, hepatic metabolic activity correlates with liver fat content.
authors.affiliation: High Field MR Centre, Department of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna, Vienna, Austria.
authors.forename: Ladislav
authors.initials: L
authors.lastname: Valkovič
authors.forename: Martin
authors.initials: M
authors.lastname: Gajdošík
authors.forename: Stefan
authors.initials: S
authors.lastname: Traussnigg
authors.forename: Peter
authors.initials: P
authors.lastname: Wolf
authors.forename: Marek
authors.initials: M
authors.lastname: Chmelík
authors.forename: Christian
authors.initials: C
authors.lastname: Kienbacher
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Bogner
authors.forename: Michael
authors.initials: M
authors.lastname: Krebs
authors.forename: Michael
authors.initials: M
authors.lastname: Trauner
authors.forename: Siegfried
authors.initials: S
authors.lastname: Trattnig
authors.forename: Martin
authors.initials: M
authors.lastname: Krššák
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000328:Adult; D000368:Aged; D000818:Animals; D001706:Biopsy; D003937:Diagnosis, Differential; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008099:Liver / Q000737:chemistry* / Q000473:pathology; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D008875:Middle Aged; D065626:Non-alcoholic Fatty Liver Disease / Q000175:diagnosis / Q000378:metabolism*; D010761:Phosphorus Radioisotopes; D015203:Reproducibility of Results; D055815:Young Adult
chemical_list: D010761:Phosphorus Radioisotopes; D000255:Adenosine Triphosphate