title: Serial study of apparent diffusion coefficient and anisotropy in patients with acute stroke.
abstract: OBJECTIVE
  We sought to characterize the evolution of apparent diffusion coefficient (ADC) and apparent diffusion anisotropy (ADA) in acute stroke and to evaluate their roles in predicting stroke evolution and outcome.
  
  
  METHODS
  We studied 26 stroke patients acutely (<24 hours), subacutely (3 to 5 days), and at outcome (3 months). Ratios of the ADC and ADA within a region of infarction and the normal contralateral region were evaluated and compared with the Canadian Neurological Scale, Barthel Index, and Rankin Scale.
  
  
  RESULTS
  Heterogeneity in ADC and ADA evolution was observed not only between patients but also within individual lesions. Three patterns of ADA evolution were observed: (1) elevated ADA acutely and subacutely; (2) elevated ADA acutely and reduced ADA subacutely; and (3) reduced ADA acutely and subacutely. At outcome, reduced ADA with elevated ADC was observed generally. We identified 3 phases of diffusion abnormalities: (1) reduced ADC and elevated ADA; (2) reduced ADC and reduced ADA; and (3) elevated ADC and reduced ADA. The ADA ratios within 12 hours correlated with the acute Canadian Neurological Scale (r=0.46, P=0.06), subacute Canadian Neurological Scale (r=0.55, P=0.02), outcome Barthel Index (r=0.62, P=0.01), and Rankin Scale (r=-0.77, P<0.0005) scores.
  
  
  CONCLUSIONS
  Combined ADC and ADA provide differential patterns of stroke evolution. Early ADA changes reflect cellular alterations in acute ischemia and may provide a potential marker to predict stroke outcome.
authors.affiliation: Department of Radiology, Royal Melbourne Hospital and University of Melbourne, Victoria, Australia. QY@radior.medrmh.unimelb.edu.au
authors.forename: Q
authors.initials: Q
authors.lastname: Yang
authors.forename: B M
authors.initials: BM
authors.lastname: Tress
authors.forename: P A
authors.initials: PA
authors.lastname: Barber
authors.forename: P M
authors.initials: PM
authors.lastname: Desmond
authors.forename: D G
authors.initials: DG
authors.lastname: Darby
authors.forename: R P
authors.initials: RP
authors.lastname: Gerraty
authors.forename: T
authors.initials: T
authors.lastname: Li
authors.forename: S M
authors.initials: SM
authors.lastname: Davis
mesh_terms: D000208:Acute Disease; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers; D002545:Brain Ischemia / Q000503:physiopathology; D002544:Cerebral Infarction / Q000503:physiopathology; D002560:Cerebrovascular Circulation / Q000502:physiology*; D003287:Contrast Media; D004058:Diffusion; D017352:Echo-Planar Imaging / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D005544:Forecasting; D006801:Humans; D007089:Image Enhancement; D007091:Image Processing, Computer-Assisted / Q000379:methods; D016014:Linear Models; D018810:Magnetic Resonance Angiography / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D009460:Neurologic Examination; D020521:Stroke / Q000145:classification / Q000503:physiopathology*; D013997:Time Factors
chemical_list: D015415:Biomarkers; D003287:Contrast Media