title: Predictors of apparent diffusion coefficient normalization in stroke patients.
abstract: OBJECTIVE
  We sought to describe the frequency of normalization of apparent diffusion coefficient (ADC) values that are decreased in hyperacute stroke and to identify characteristics of tissue demonstrating normalization.
  
  
  METHODS
  Sixty-eight acute ischemic stroke patients underwent MRI examination (including diffusion/perfusion imaging and MR angiography) within 6 hours (mean, 2.8 hours) after symptom onset, after 24 hours, and again 4 to 7 days later. Lesion volumes with decreased ADC and delayed time to peak in perfusion imaging were determined. In patients showing ADC normalization, volumes with ADC decrease graded as <50%, 50% to 60%, 60% to 70%, and 70% to 80% of the contralateral value were determined by thresholding. Patients were categorized as normalizers (demonstrating ADC normalization in >5 mL tissue with initially decreased ADC) or nonnormalizers (demonstrating ADC normalization in <5 mL tissue).
  
  
  RESULTS
  Fourteen patients (19.7%) were classified as normalizers. Eleven of 31 patients (35.5%) initially imaged <3 hours after stroke onset and 3 of 37 (7.5%) of those imaged 3 to 6 hours after onset were normalizers. ADC normalization occurred predominantly in the basal ganglia and white matter after thrombolytic therapy in patients with more distal vessel occlusions. All normalizers demonstrated at least partial tissue reperfusion. Tissue with more severe initial decrease in ADC was less likely to demonstrate normalization.
  
  
  CONCLUSIONS
  ADC normalization is not a rare event in acute stroke after tissue reperfusion. Brain tissue with initially decreased ADC, especially within 3 hours after stroke onset, may include "tissue at risk."
authors.affiliation: Department of Neuroradiology, University Hospital Eppendorf, University of Hamburg, Hamburg, Germany. fiehler@uke.uni-hamburg.de
authors.forename: Jens
authors.initials: J
authors.lastname: Fiehler
authors.forename: Karina
authors.initials: K
authors.lastname: Knudsen
authors.forename: Thomas
authors.initials: T
authors.lastname: Kucinski
authors.forename: Chelsea S
authors.initials: CS
authors.lastname: Kidwell
authors.forename: Jeffry R
authors.initials: JR
authors.lastname: Alger
authors.forename: Götz
authors.initials: G
authors.lastname: Thomalla
authors.forename: Bernd
authors.initials: B
authors.lastname: Eckert
authors.forename: Oliver
authors.initials: O
authors.lastname: Wittkugel
authors.forename: Cornelius
authors.initials: C
authors.lastname: Weiller
authors.forename: Hermann
authors.initials: H
authors.lastname: Zeumer
authors.forename: Joachim
authors.initials: J
authors.lastname: Röther
mesh_terms: D000208:Acute Disease; D000328:Adult; D000368:Aged; D002545:Brain Ischemia / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology*; D004058:Diffusion; D038524:Diffusion Magnetic Resonance Imaging; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D020521:Stroke / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology*; D013997:Time Factors