title: Non-invasive estimation of hepatic glucose uptake from [18F]FDG PET images using tissue-derived input functions.
abstract: OBJECTIVE
  The liver is perfused through the portal vein and hepatic artery. Quantification of hepatic glucose uptake (HGU) using PET requires the use of an input function for both the hepatic artery and portal vein. The former can be generally obtained invasively, but blood withdrawal from the portal vein is not practical in humans. The aim of this study was to develop and validate a new technique to obtain quantitative HGU by estimating the input function from PET images.
  
  
  METHODS
  Normal pigs (n = 12) were studied with [18F]FDG PET, in which arterial and portal blood time-activity curves (TAC) were determined invasively to serve as reference measurements. The present technique consisted of two characteristics, i.e. using a model input function and simultaneously fitting multiple liver tissue TACs from images by minimizing the residual sum of square between the tissue TACs and fitted curves. The input function was obtained from the parameters determined from the fitting. The HGU values were computed by the estimated and measured input functions and compared between the methods.
  
  
  RESULTS
  The estimated input functions were well reproduced. The HGU values, ranging from 0.005 to 0.02 ml/min per ml, were not significantly different between the two methods (r = 0.95, p < 0.001). A Bland-Altman plot demonstrated a small overestimation by the image-derived method with a bias of 0.00052 ml/min per g for HGU.
  
  
  CONCLUSIONS
  The results presented demonstrate that the input function can be estimated directly from the PET image, supporting the fully non-invasive assessment of liver glucose metabolism in human studies.
authors.affiliation: Turku PET Centre, University of Turku, PO Box 52, 20521 Turku, Finland. nobuyuki.kudomi@tyks.fi
authors.forename: N
authors.initials: N
authors.lastname: Kudomi
authors.forename: M J
authors.initials: MJ
authors.lastname: Järvisalo
authors.forename: J
authors.initials: J
authors.lastname: Kiss
authors.forename: R
authors.initials: R
authors.lastname: Borra
authors.forename: A
authors.initials: A
authors.lastname: Viljanen
authors.forename: T
authors.initials: T
authors.lastname: Viljanen
authors.forename: T
authors.initials: T
authors.lastname: Savunen
authors.forename: J
authors.initials: J
authors.lastname: Knuuti
authors.forename: H
authors.initials: H
authors.lastname: Iida
authors.forename: P
authors.initials: P
authors.lastname: Nuutila
authors.forename: P
authors.initials: P
authors.lastname: Iozzo
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D005215:Fasting; D019788:Fluorodeoxyglucose F18; D005947:Glucose / Q000378:metabolism*; D007091:Image Processing, Computer-Assisted; D007328:Insulin / Q000494:pharmacology; D008099:Liver / Q000000981:diagnostic imaging* / Q000187:drug effects / Q000378:metabolism*; D008954:Models, Biological; D049268:Positron-Emission Tomography; D015203:Reproducibility of Results; D013552:Swine
chemical_list: D007328:Insulin; D019788:Fluorodeoxyglucose F18; D005947:Glucose