title: Quantification of Task-Specific Glucose Metabolism with Constant Infusion of 18F-FDG.
abstract: The investigation of cerebral metabolic rate of glucose (CMRGlu) at baseline and during specific tasks previously required separate scans with the drawback of high intrasubject variability. We aimed to validate a novel approach to assessing baseline glucose metabolism and task-specific changes in a single measurement with a constant infusion of18F-FDG.
  
  
  METHODS
  Fifteen healthy subjects underwent two PET measurements with arterial blood sampling. As a reference, baseline CMRGlu was quantified from a 60-min scan after18F-FDG bolus application using the Patlak plot (eyes closed). For the other scan, a constant radioligand infusion was applied for 95 min, during which the subjects opened their eyes at 10-20 min and 60-70 min and tapped their right thumb to their fingers at 35-45 min and 85-95 min. The constant-infusion scan was quantified in two steps. First, the general linear model was used to fit regional time-activity curves with regressors for baseline metabolism, task-specific changes for the eyes-open and finger-tapping conditions, and movement parameters. Second, the Patlak plot was used for quantification of CMRGlu. Multiplication of the baseline regressor by β-values from the general linear model yielded regionally specific time-activity curves for baseline metabolism. Further, task-specific changes in metabolism are directly proportional to changes in the slope of the time-activity curve and hence to changes in CMRGlu.
  
  
  RESULTS
  Baseline CMRGlu from the constant-infusion scan matched that from the bolus application (test-retest variability, 1.1% ± 24.7%), which was not the case for a previously suggested approach (variability, -39.9% ± 25.2%, P < 0.001). Task-specific CMRGlu increased in the primary visual and motor cortices for eyes open and finger tapping, respectively (P < 0.05, familywise error-corrected), with absolute changes of up to 2.1 μmol/100 g/min and 6.3% relative to baseline. For eyes open, a decreased CMRGlu was observed in default-mode regions (P < 0.05, familywise error-corrected). CMRGlu quantified with venous blood samples (n = 6) showed excellent agreement with results obtained from arterial samples (r > 0.99).
  
  
  CONCLUSIONS
  Baseline glucose metabolism and task-specific changes can be quantified in a single measurement with constant infusion of18F-FDG and venous blood sampling. The high sensitivity and regional specificity of the approach offer novel possibilities for functional and multimodal brain imaging.
authors.affiliation: Department of Psychiatry and Psychotherapy, Medical University of Vienna, Vienna, Austria; and.
authors.forename: Andreas
authors.initials: A
authors.lastname: Hahn
authors.affiliation: Department of Psychiatry and Psychotherapy, Medical University of Vienna, Vienna, Austria; and.
authors.forename: Gregor
authors.initials: G
authors.lastname: Gryglewski
authors.affiliation: Department of Biomedical Imaging and Image-Guided Therapy, Division of Nuclear Medicine, Medical University of Vienna, Vienna, Austria.
authors.forename: Lukas
authors.initials: L
authors.lastname: Nics
authors.affiliation: Department of Psychiatry and Psychotherapy, Medical University of Vienna, Vienna, Austria; and.
authors.forename: Marius
authors.initials: M
authors.lastname: Hienert
authors.affiliation: Department of Psychiatry and Psychotherapy, Medical University of Vienna, Vienna, Austria; and.
authors.forename: Lucas
authors.initials: L
authors.lastname: Rischka
authors.affiliation: Department of Biomedical Imaging and Image-Guided Therapy, Division of Nuclear Medicine, Medical University of Vienna, Vienna, Austria.
authors.forename: Chrysoula
authors.initials: C
authors.lastname: Vraka
authors.affiliation: Department of Psychiatry and Psychotherapy, Medical University of Vienna, Vienna, Austria; and.
authors.forename: Helen
authors.initials: H
authors.lastname: Sigurdardottir
authors.affiliation: Department of Psychiatry and Psychotherapy, Medical University of Vienna, Vienna, Austria; and.
authors.forename: Thomas
authors.initials: T
authors.lastname: Vanicek
authors.affiliation: Department of Psychiatry and Psychotherapy, Medical University of Vienna, Vienna, Austria; and.
authors.forename: Gregory M
authors.initials: GM
authors.lastname: James
authors.affiliation: Department of Psychiatry and Psychotherapy, Medical University of Vienna, Vienna, Austria; and.
authors.forename: René
authors.initials: R
authors.lastname: Seiger
authors.affiliation: Department of Psychiatry and Psychotherapy, Medical University of Vienna, Vienna, Austria; and.
authors.forename: Alexander
authors.initials: A
authors.lastname: Kautzky
authors.affiliation: Department of Psychiatry and Psychotherapy, Medical University of Vienna, Vienna, Austria; and.
authors.forename: Leo
authors.initials: L
authors.lastname: Silberbauer
authors.affiliation: Department of Biomedical Imaging and Image-Guided Therapy, Division of Nuclear Medicine, Medical University of Vienna, Vienna, Austria.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Wadsak
authors.affiliation: Department of Biomedical Imaging and Image-Guided Therapy, Division of Nuclear Medicine, Medical University of Vienna, Vienna, Austria.
authors.forename: Markus
authors.initials: M
authors.lastname: Mitterhauser
authors.affiliation: Department of Biomedical Imaging and Image-Guided Therapy, Division of Nuclear Medicine, Medical University of Vienna, Vienna, Austria.
authors.forename: Marcus
authors.initials: M
authors.lastname: Hacker
authors.affiliation: Department of Psychiatry and Psychotherapy, Medical University of Vienna, Vienna, Austria; and.
authors.forename: Siegfried
authors.initials: S
authors.lastname: Kasper
authors.affiliation: Department of Psychiatry and Psychotherapy, Medical University of Vienna, Vienna, Austria; and rupert.lanzenberger@meduniwien.ac.at.
authors.forename: Rupert
authors.initials: R
authors.lastname: Lanzenberger
mesh_terms: D000328:Adult; D001921:Brain / Q000000981:diagnostic imaging / Q000378:metabolism; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000008:administration & dosage*; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D008297:Male; D049268:Positron-Emission Tomography / Q000379:methods*
chemical_list: D019788:Fluorodeoxyglucose F18; D005947:Glucose
keywords: glucose metabolism; positron emission tomography; quantification; task