title: Detectability of hypometabolic regions in mild Alzheimer disease: function of time after the injection of 2-[fluorine 18]-fluoro-2-deoxy-D-glucose.
abstract: OBJECTIVE
  2-[Fluorine 18]-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) has played an important role in detecting hypometabolic regions in the brains of patients with dementia. To our knowledge, the optimal imaging time for dementia has not been investigated. The aim of this study was to evaluate the sensitivity of the early scanning (ES) compared with late scanning (LS) for demonstrating decreased regional glucose metabolism in patients with Alzheimer disease (AD).
  
  
  METHODS
  Twenty patients with mild AD (mean age +/- standard deviation, 64.8 +/- 5.2 years) and 20 age- and sex-matched healthy volunteers (age, 65.9 +/- 4.5 years) were underwent FDG PET. Their cerebral glucose metabolic images were obtained on ES at 30-42 minutes and LS at 60-72 minutes after the administration of FDG 185-346 MBq. We compared regional cerebral metabolic images in a voxel-by-voxel analysis with statistical parametric mapping between patients with AD and control subjects and evaluated the difference in the hypometabolic regions between the two scans.
  
  
  RESULTS
  In the AD-to-healthy comparison, LS at the P < .001 level of significance showed more extensive and significant hypometabolic areas than did ES.
  
  
  CONCLUSIONS
  These results indicate that LS is superior to ES in detecting hypometabolic regions in patients with AD. For patients with AD, emission scanning soon after the administration of FDG is probably not advised.
authors.affiliation: Department of Radiology, Hyogo Brain and Heart Center, Himeji, Hyogo, Japan.
authors.forename: Setsu
authors.initials: S
authors.lastname: Sakamoto
authors.forename: Kazunari
authors.initials: K
authors.lastname: Ishii
authors.forename: Kayo
authors.initials: K
authors.lastname: Hosaka
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Mori
authors.forename: Masahiro
authors.initials: M
authors.lastname: Sasaki
authors.forename: Etsuro
authors.initials: E
authors.lastname: Mori
mesh_terms: D000368:Aged; D000544:Alzheimer Disease / Q000000981:diagnostic imaging* / Q000378:metabolism*; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000008:administration & dosage; D006801:Humans; D007267:Injections; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals / Q000008:administration & dosage; D012720:Severity of Illness Index; D013997:Time Factors
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18