title: Hypoperfusion intensity ratio predicts infarct progression and functional outcome in the DEFUSE 2 Cohort.
abstract: OBJECTIVE
  We evaluate associations between the severity of magnetic resonance perfusion-weighted imaging abnormalities, as assessed by the hypoperfusion intensity ratio (HIR), on infarct progression and functional outcome in the Diffusion and Perfusion Imaging Evaluation for Understanding Stroke Evolution Study 2 (DEFUSE 2).
  
  
  METHODS
  Diffusion-weighted magnetic resonance imaging and perfusion-weighted imaging lesion volumes were determined with the RAPID software program. HIR was defined as the proportion of TMax >6 s lesion volume with a Tmax >10 s delay and was dichotomized based on its median value (0.4) into low versus high subgroups as well as quartiles. Final infarct volumes were assessed at day 5. Initial infarct growth velocity was calculated as the baseline diffusion-weighted imaging (DWI) lesion volume divided by the delay from symptom onset to baseline magnetic resonance imaging. Total Infarct growth was determined by the difference between final infarct and baseline DWI volumes. Collateral flow was assessed on conventional angiography and dichotomized into good and poor flow. Good functional outcome was defined as modified Rankin Scale ≤2 at 90 days.
  
  
  RESULTS
  Ninety-nine patients were included; baseline DWI, perfusion-weighted imaging, and final infarct volumes increased with HIR quartiles (P<0.01). A high HIR predicted poor collaterals with an area under the curve of 0.73. Initial infarct growth velocity and total infarct growth were greater among patients with a high HIR (P<0.001). After adjustment for age, DWI volume, and reperfusion, a low HIR was associated with good functional outcome: odds ratio=4.4 (95% CI, 1.3-14.3); P=0.014.
  
  
  CONCLUSIONS
  HIR can be easily assessed on automatically processed perfusion maps and predicts the rate of collateral flow, infarct growth, and clinical outcome.
authors.affiliation: From the Department of Neurology and Neurosciences, Stanford Stroke Center, CA.
authors.forename: Jean Marc
authors.initials: JM
authors.lastname: Olivot
authors.forename: Michael
authors.initials: M
authors.lastname: Mlynash
authors.forename: Manabu
authors.initials: M
authors.lastname: Inoue
authors.forename: Michael P
authors.initials: MP
authors.lastname: Marks
authors.forename: Hayley M
authors.initials: HM
authors.lastname: Wheeler
authors.forename: Stephanie
authors.initials: S
authors.lastname: Kemp
authors.forename: Matus
authors.initials: M
authors.lastname: Straka
authors.forename: Gregory
authors.initials: G
authors.lastname: Zaharchuk
authors.forename: Roland
authors.initials: R
authors.lastname: Bammer
authors.forename: Maarten G
authors.initials: MG
authors.lastname: Lansberg
authors.forename: Gregory W
authors.initials: GW
authors.lastname: Albers
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002544:Cerebral Infarction / Q000473:pathology* / Q000503:physiopathology; D002560:Cerebrovascular Circulation / Q000502:physiology; D003287:Contrast Media; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D018450:Disease Progression; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D055420:Perfusion Imaging / Q000379:methods*; D011237:Predictive Value of Tests; D020127:Recovery of Function; D012720:Severity of Illness Index; D012984:Software; D020521:Stroke / Q000473:pathology* / Q000503:physiopathology
chemical_list: D003287:Contrast Media
keywords: brain infarction; magnetic resonance imaging; perfusion imaging