title: Whole-body PET: physiological and artifactual fluorodeoxyglucose accumulations.
abstract: The purpose of this study was to semiquantitatively identify artifactual and physiological soft-tissue accumulations in whole-body FDG-PET scans with the aim of defining their frequency and anatomic distribution.
  
  
  METHODS
  Fifty whole-body FDG-PET scans performed for the staging of malignant melanoma were obtained from transaxial scans and reconstructed without absorption correction by filtered backprojection in the form of coronal and sagittal sections. The patients were asked to stay n.p.o. for at least 4 hr and interrogated about their physical activity prior to injection and until scanning. Classification of FDG organ accumulations was done using grades 0-6. Means and standard deviations on this scale were then calculated for multiple organs and muscle groups and tabulated.
  
  
  RESULTS
  On this grading scale, viscera showed uptake grades between 1.7 +/- 0.5 and 2.05 +/- 1.0. Except for the intestines, the activity in these organs was homogeneously distributed. Relatively high average uptake values of 2.0-4.2 (s.d. > or = 2.3) were found in various muscle groups, especially the orbital musculature. Myocardial uptake was visible in 90% of the scans. Reconstruction artifacts were seen around the renal collecting system and the bladder.
  
  
  CONCLUSIONS
  Most of the "normal" accumulations of FDG in nonattenuation corrected whole-body PET are readily recognized and distinct from the usually focal FDG accumulation associated with metastatic disease, but the diagnostician must be familiar with them. Muscular FDG uptake is related to physical activity prior and immediately following injection and can be minimized by proper patient instructions and positioning.
authors.affiliation: Department of Medical Radiology, University Hospital, Zürich, Switzerland.
authors.forename: H
authors.initials: H
authors.lastname: Engel
authors.forename: H
authors.initials: H
authors.lastname: Steinert
authors.forename: A
authors.initials: A
authors.lastname: Buck
authors.forename: T
authors.initials: T
authors.lastname: Berthold
authors.forename: R A
authors.initials: RA
authors.lastname: Huch Böni
authors.forename: G K
authors.initials: GK
authors.lastname: von Schulthess
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016477:Artifacts; D003847:Deoxyglucose / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D015444:Exercise; D005260:Female; D005462:Fluorine Radioisotopes / Q000493:pharmacokinetics; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007422:Intestines / Q000000981:diagnostic imaging; D008297:Male; D008545:Melanoma / Q000000981:diagnostic imaging* / Q000473:pathology / Q000556:secondary; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging; D009367:Neoplasm Staging; D014018:Tissue Distribution; D014055:Tomography, Emission-Computed / Q000379:methods*
chemical_list: D005462:Fluorine Radioisotopes; D019788:Fluorodeoxyglucose F18; D003847:Deoxyglucose