title: Estimating the amount of FDG uptake in physiological tissues.
abstract: BACKGROUND
  It is known that for a fixed amount of injected tracer, the amount available for a tissue of interest will be less if other tissues show intense uptake. The aim of this study was to estimate the magnitude of 2-deoxy-2-[(18)F]fluoro-D-glucose (18FDG) uptake amount in physiological tissues that may show an intense uptake in current clinical practice.
  
  
  METHODS
  A formula was established providing an estimate of the percentage of injected 18FDG molecules (P; in %) that are irreversibly trapped in an 18FDG-positive tissue during a PET examination.
  
  
  RESULTS
  P ≅ 0.17*exp(-λt(acq))*TLG/W, where λ is the (18)F physical decay constant, t(acq) is the injection-acquisition time delay, TLG is total lesion glycolysis (g) and W is the patient weight (kg). The magnitude of P was calculated in two patients showing an intense uptake in brown fat, myocardium and bowels: 0.5, 3.5, and 4.2% respectively.
  
  
  CONCLUSIONS
  A formula is available to quickly estimate the amount of 18FDG uptake in tissues. We suggest that the accumulation of different physiological uptakes may actually affect SUV quantification in a tissue of interest.
authors: CHU de Bordeaux, Service de Médecine Nucléaire, F-33604 Pessac, France; Université de Bordeaux 2, Centre de Recherche Cardio-Thoracique, F-33076 Bordeaux, France; INSERM U 1045, Centre de Recherche Cardio-Thoracique, F-33076 Bordeaux, France. Electronic address: elaffon@u-bordeaux2.fr.
authors: E
authors: E
authors: Laffon
authors: CHU de Bordeaux, Service de Médecine Nucléaire, F-33604 Pessac, France.
authors: H
authors: H
authors: de Clermont
authors: CHU de Bordeaux, Service de Médecine Nucléaire, F-33604 Pessac, France.
authors: F
authors: F
authors: Lamare
authors: Université de Bordeaux 2, Centre de Recherche Cardio-Thoracique, F-33076 Bordeaux, France; INSERM U 1045, Centre de Recherche Cardio-Thoracique, F-33076 Bordeaux, France.
authors: R
authors: R
authors: Marthan
mesh_terms: D000328:Adult; D000465:Algorithms; D001822:Body Burden; D001835:Body Weight; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008657:Metabolic Clearance Rate; D008875:Middle Aged; D008954:Models, Biological; D009928:Organ Specificity; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D014018:Tissue Distribution
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
keywords: 18FDG PET; Biologic factor; Physiological tissue uptake; SUV; TLG