title: Reduction of FDG uptake in brown adipose tissue in clinical patients by a single dose of propranolol.
abstract: OBJECTIVE
  Uptake in brown adipose tissue (hibernating fat) is sometimes seen at FDG-PET examinations. Despite a characteristic appearance, this may hide clinically relevant uptake. Stimulation of the sympathetic nervous system increases glucose uptake of brown fat. We now re-examine patients with brown fat activity that could disguise tumour uptake after pre-treatment with propranolol (a non-selective beta-blocker) in order to reduce the uptake. Our first examinations of this kind are reported.
  
  
  METHODS
  Eleven patients with strong brown fat uptake were studied. There was a mean of 5 days (range 2-8) between the examinations. At the second examination, 80 mg of propranolol was given orally 2 h before FDG administration. In addition to visual evaluation of the brown fat uptake, SUV assessments of the uptake in brown fat, lung, heart, liver, spleen and bone marrow were made.
  
  
  RESULTS
  All patients showed complete or almost complete disappearance of the brown fat activity at the second examination (p < 0.001) both upon visual evaluation and when comparing SUVs. In seven patients there was also uptake in a known or strongly suspected malignancy, which remained unchanged between the examinations. Beyond an insignificant decrease in the myocardial uptake, there was no redistribution to the various examined organs at the second examination.
  
  
  CONCLUSIONS
  Pre-treatment with a single dose of propranolol blocks the FDG uptake in brown adipose tissue, thereby increasing the specificity of the examination. The tumour uptake seems not to be impaired.
authors.affiliation: Department of Radiology, Karolinska University Hospital, 171 76 Stockholm, Sweden. veli.soderlund@karolinska.se
authors.forename: Veli
authors.initials: V
authors.lastname: Söderlund
authors.forename: Stig A
authors.initials: SA
authors.lastname: Larsson
authors.forename: Hans
authors.initials: H
authors.lastname: Jacobsson
mesh_terms: D002001:Adipose Tissue, Brown / Q000000981:diagnostic imaging* / Q000187:drug effects / Q000378:metabolism*; D000328:Adult; D016477:Artifacts; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D008297:Male; D008657:Metabolic Clearance Rate / Q000187:drug effects; D008875:Middle Aged; D009369:Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism; D011433:Propranolol / Q000008:administration & dosage*; D011877:Radionuclide Imaging
chemical_list: D019788:Fluorodeoxyglucose F18; D011433:Propranolol