title: Metabolic liver function measured in vivo by dynamic (18)F-FDGal PET/CT without arterial blood sampling.
abstract: BACKGROUND
  Metabolic liver function can be measured by dynamic PET/CT with the radio-labelled galactose-analogue 2-[(18)F]fluoro-2-deoxy-D-galactose ((18)F-FDGal) in terms of hepatic systemic clearance of (18)F-FDGal (K, ml blood/ml liver tissue/min). The method requires arterial blood sampling from a radial artery (arterial input function), and the aim of this study was to develop a method for extracting an image-derived, non-invasive input function from a volume of interest (VOI).
  
  
  METHODS
  Dynamic (18)F-FDGal PET/CT data from 16 subjects without liver disease (healthy subjects) and 16 patients with liver cirrhosis were included in the study. Five different input VOIs were tested: four in the abdominal aorta and one in the left ventricle of the heart. Arterial input function from manual blood sampling was available for all subjects. K*-values were calculated using time-activity curves (TACs) from each VOI as input and compared to the K-value calculated using arterial blood samples as input. Each input VOI was tested on PET data reconstructed with and without resolution modelling.
  
  
  RESULTS
  All five image-derived input VOIs yielded K*-values that correlated significantly with K calculated using arterial blood samples. Furthermore, TACs from two different VOIs yielded K*-values that did not statistically deviate from K calculated using arterial blood samples. A semicircle drawn in the posterior part of the abdominal aorta was the only VOI that was successful for both healthy subjects and patients as well as for PET data reconstructed with and without resolution modelling.
  
  
  CONCLUSIONS
  Metabolic liver function using (18)F-FDGal PET/CT can be measured without arterial blood samples by using input data from a semicircle VOI drawn in the posterior part of the abdominal aorta.
authors.affiliation: Department of Nuclear Medicine & PET Centre, Aarhus University Hospital, DK-8000 Aarhus, Denmark.
authors.forename: Jacob
authors.initials: J
authors.lastname: Horsager
authors.affiliation: Department of Nuclear Medicine & PET Centre, Aarhus University Hospital, DK-8000 Aarhus, Denmark.
authors.forename: Ole Lajord
authors.initials: OL
authors.lastname: Munk
authors.affiliation: Department of Nuclear Medicine & PET Centre, Aarhus University Hospital, DK-8000 Aarhus, Denmark ; Department of Hepatology & Gastroenterology, Aarhus University Hospital, Noerrebrogade 44, DK-8000 Aarhus C, Denmark.
authors.forename: Michael
authors.initials: M
authors.lastname: Sørensen
keywords: Dynamic PET/CT; Galactose; Image-derived input; Metabolic liver function; Non-invasive