title: Hepatic steatosis is associated with increased hepatic FDG uptake.
abstract: OBJECTIVE
  The use of liver as a reference tissue for semi-quantification of tumour FDG uptake may not be valid in hepatic steatosis (HS). Previous studies on the relation between liver FDG uptake and HS have been contradictory probably because they ignored blood glucose (BG). Because hepatocyte and blood FDG concentrations equalize, liver FDG uptake parallels BG, which must therefore be considered when studying hepatic FDG uptake. We therefore re-examined the relation between HS and liver uptake taking BG into account.
  
  
  METHODS
  This was a retrospective study of 304 patients undergoing routine PET/CT with imaging 60min post-FDG. Average standard uptake value (SUVave), maximum SUV (SUVmax) and CT density (index of HS) were measured in a liver ROI. Blood pool SUV was based on the left ventricular cavity (SUVLV). Correlations were assessed using least squares fitting of continuous data. Patients were also divided into BG subgroups (<4, 4-5, 5-6, 6-8, 8-10 and 10+mmol/l).
  
  
  RESULTS
  SUVave, SUVmax and SUVLV displayed similar relations with BG. SUVmax/SUVLV, but not SUVave/SUVLV, correlated significantly with BG. SUVmax, but not SUVave, correlated inversely with CT density before and after adjusting for BG. SUVmax/SUVave correlated more strongly with CT density than SUVmax. CT density correlated inversely with SUVmax/SUVLV but positively with SUVave/SUVLV.
  
  
  CONCLUSIONS
  Hepatic SUV is more influenced by BG than by HS. Its relation with BG renders it unsuitable as a reference tissue. Nevertheless, hepatic fat does correlate positively with liver SUV, although this is seen only with SUVmax because SUVave is 'diluted' by hepatic fat.
authors.affiliation: Clinical Imaging Sciences Centre, Brighton Sussex Medical School, Brighton, UK; Department of Nuclear Medicine, Brighton Sussex University Hospitals NHS Trust, Brighton, UK. Electronic address: G.Keramida@bsms.ac.uk.
authors.forename: Georgia
authors.initials: G
authors.lastname: Keramida
authors.affiliation: Department of Medicine, Brighton Sussex University Hospitals NHS Trust, Brighton, UK.
authors.forename: Jon
authors.initials: J
authors.lastname: Potts
authors.affiliation: Clinical Imaging Sciences Centre, Brighton Sussex Medical School, Brighton, UK.
authors.forename: Janice
authors.initials: J
authors.lastname: Bush
authors.affiliation: Clinical Imaging Sciences Centre, Brighton Sussex Medical School, Brighton, UK; Department of Nuclear Medicine, Brighton Sussex University Hospitals NHS Trust, Brighton, UK.
authors.forename: Sabina
authors.initials: S
authors.lastname: Dizdarevic
authors.affiliation: Clinical Imaging Sciences Centre, Brighton Sussex Medical School, Brighton, UK; Department of Nuclear Medicine, Brighton Sussex University Hospitals NHS Trust, Brighton, UK.
authors.forename: A Michael
authors.initials: AM
authors.lastname: Peters
mesh_terms: D003198:Computer Simulation; D005234:Fatty Liver / Q000000981:diagnostic imaging*; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008099:Liver / Q000000981:diagnostic imaging* / Q000378:metabolism*; D008954:Models, Biological; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D015854:Up-Regulation
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
keywords: FDG; Glucose; Hepatic steatosis; Standard uptake value