title: Relationships of body habitus and SUV indices with signal-to-noise ratio of hepatic (18)F-FDG PET.
abstract: OBJECTIVE
  Tissue accumulation of (18)F-FDG is quantified as standardised uptake value (SUV), which may be expressed as the voxel maximum (SUVmax) or mean (SUVmean). SUVmax/SUVmean may be a marker of hepatic steatosis, while the coefficient of variation (CV) of SUV may be a marker of hepatic fat distribution heterogeneity (HFDH). Alternatively, they may reflect low signal-to-noise ratio ('noise') in obese persons in whom hepatic steatosis is common. The study aim was to compare the impact of body size on noise versus SUV and CT density (CTD).
  
  
  METHODS
  Dynamic PET was performed (30×1min frames) following FDG injection in 60 patients undergoing routine PET/CT. Hepatic FDG clearance was measured using Patlak-Rutland graphical analysis with abdominal aorta as input. Noise was quantified as the standard deviation (SD) of the plot residuals (ignoring the first 2 frames), normalised to the intercept (NRMSD). SUVmax, SUVmean and CTD were measured from 60min whole body PET/CT. CV of SUV and SD of CTD were quantified in 28/60 patients using texture analysis.
  
  
  RESULTS
  NRMSD correlated with weight (r=0.49; p<0.0001) and BMI (r=0.48; p=0.0001). SUVmax, SUVmean, SUVmax/SUVmean, CV of SUV, CTD, and SD of CTD all correlated strongly with weight and BMI (p<0.0001). However, they correlated weakly with NRMSD, the strongest being SUVmax (r=0.34; p=0.008) and SD of CTD (r=0.42; n=28; p=0.026).
  
  
  CONCLUSIONS
  Noise is increased in overweight/obese persons but has little effect on SUV indices, CTD and their variabilities. SUVmax/SUVmean and CV of SUV are therefore, to some extent, markers of hepatic steatosis and HFDH, respectively.
authors.affiliation: Clinical Imaging Sciences Centre, Brighton and Sussex Medical School, Brighton, UK.
authors.forename: G
authors.initials: G
authors.lastname: Keramida
authors.affiliation: Department of Nuclear Medicine, Brighton and Sussex University Hospitals NHS Trust, Brighton, UK.
authors.forename: A
authors.initials: A
authors.lastname: Dunford
authors.affiliation: Imaging Sciences and Biomedical Engineering, King's College, London, UK.
authors.forename: M
authors.initials: M
authors.lastname: Siddique
authors.affiliation: Imaging Sciences and Biomedical Engineering, King's College, London, UK.
authors.forename: G J
authors.initials: GJ
authors.lastname: Cook
authors.affiliation: Division of Clinical and Laboratory Investigation, Brighton and Sussex Medical School, Brighton, UK. Electronic address: a.m.peters@bsms.ac.uk.
authors.forename: A M
authors.initials: AM
authors.lastname: Peters
mesh_terms: D000328:Adult; D000368:Aged; D005234:Fatty Liver / Q000000981:diagnostic imaging*; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics*; D006801:Humans; D050152:Intra-Abdominal Fat / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000503:physiopathology; D050177:Overweight / Q000503:physiopathology; D000072078:Positron Emission Tomography Computed Tomography / Q000379:methods; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics*; D059629:Signal-To-Noise Ratio
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
keywords: FDG; Obesity; PET/CT; Signal-to-noise ratio; Standardised uptake value