title: Identifying hypoxic tissue after acute ischemic stroke using PET and 18F-fluoromisonidazole.
abstract: OBJECTIVE
  To show that PET with 18F-fluoromisonidazole (18F-FMISO) can detect peri-infarct hypoxic tissue in patients after ischemic stroke.
  
  
  BACKGROUND
  PET with (15)O-labeled oxygen and water is the only established method for identifying the ischemic penumbra in humans. We used PET with 18F-FMISO in patients after ischemic stroke to identify hypoxic but viable peri-infarct tissue likely to represent the ischemic penumbra, and to determine how long hypoxic tissues persist after stroke.
  
  
  METHODS
  Patients with acute hemispheric ischemic stroke were studied using PET with 18F-FMISO either within 48 hours or 6 to 11 days after stroke onset. The final infarct was defined by CT performed 6 to 11 days after stroke. Tracer uptake was assessed objectively by calculating the mean activity in the contralateral (normal) hemisphere, then identifying pixels with activity greater than 3 SDs above the mean in both hemispheres. Positive studies were those with high-activity pixels ipsilateral to the infarct.
  
  
  RESULTS
  Fifteen patients were studied; 13 within 48 hours of stroke, 8 at 6 to 11 days, and 6 during both time periods. Hypoxic tissue was detected in 9 of the 13 patients studied within 48 hours of stroke, generally distributed in the peripheries of the infarct and adjacent peri-infarct tissues. None of the 8 patients studied 6 to 11 days after stroke exhibited increased 18F-FMISO activity. All 6 patients studied both early and late exhibited areas of increased activity during the early but not the late study.
  
  
  CONCLUSIONS
  PET with 18F-FMISO can detect peri-infarct hypoxic tissue after acute ischemic stroke. The distribution of hypoxic tissue suggests that it may represent the ischemic penumbra. Hypoxic tissues do not persist to the subacute phase of stroke (6 to 11 days).
authors.affiliation: Department of Neurology, Austin & Repatriation Medical Centre, Heidelberg, Vic, Australia.
authors.forename: S J
authors.initials: SJ
authors.lastname: Read
authors.forename: T
authors.initials: T
authors.lastname: Hirano
authors.forename: D F
authors.initials: DF
authors.lastname: Abbott
authors.forename: J I
authors.initials: JI
authors.lastname: Sachinidis
authors.forename: H J
authors.initials: HJ
authors.lastname: Tochon-Danguy
authors.forename: J G
authors.initials: JG
authors.lastname: Chan
authors.forename: G F
authors.initials: GF
authors.lastname: Egan
authors.forename: A M
authors.initials: AM
authors.lastname: Scott
authors.forename: C F
authors.initials: CF
authors.lastname: Bladin
authors.forename: W J
authors.initials: WJ
authors.lastname: McKay
authors.forename: G A
authors.initials: GA
authors.lastname: Donnan
mesh_terms: D000208:Acute Disease; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002561:Cerebrovascular Disorders / Q000000981:diagnostic imaging*; D005260:Female; D005462:Fluorine Radioisotopes; D006801:Humans; D002534:Hypoxia, Brain / Q000000981:diagnostic imaging*; D008297:Male; D008920:Misonidazole / Q000031:analogs & derivatives*; D011838:Radiation-Sensitizing Agents; D014055:Tomography, Emission-Computed; D014057:Tomography, X-Ray Computed
chemical_list: D005462:Fluorine Radioisotopes; D011838:Radiation-Sensitizing Agents; C031843:fluoromisonidazole; D008920:Misonidazole