title: Signal evolution and infarction risk for apparent diffusion coefficient lesions in acute ischemic stroke are both time- and perfusion-dependent.
abstract: OBJECTIVE
  This study aimed to examine the temporal relationship between tissue perfusion and apparent diffusion coefficient (ADC) changes within 6 hours of ischemic stroke onset and how different reperfusion patterns may affect tissue outcome in ADC lesions.
  
  
  METHODS
  Thirty-one participants were sequentially imaged at 3 hours, 6 hours, and 1 month post-stroke. Three regions of interest (ROIs) were defined within initial ADC lesions: ROI (1)reperf_3hour hyperacute reperfusion (within 3 hours), ROI (2)reperf_6hour acute reperfusion (3 to 6 hours), and ROI (3)nonreperf no reperfusion (by 6 hours). For each ROI, changes in ADC (ΔADC) from 3 to 6 hours and risks of infarction were examined.
  
  
  RESULTS
  The magnitude of initial ADC reduction was similar in all 3 ROIs (P=0.51). ΔADC was strongly associated with reperfusion (P<0.0001) but not with initial ADC reduction (P=0.83). ΔADC in ROI (1)reperf_3hour and ROI (2)reperf_6hour was significantly larger than that of ROI (3)nonreperf (P<0.05). Positive ΔADC was obtained from 3 to 6 hours in ROI (1)reperf_3hour that had restored perfusion before 3 hours, demonstrating a temporal delay between reperfusion and ADC changes. Risks of infarction were significantly higher in ROI (3)nonreperf than those in ROI (1)reperf_3hour and ROI (2)reperf_6hour.
  
  
  CONCLUSIONS
  Improvement in ADC did not occur coincidently with reperfusion but showed a temporal delay. Regions with similar initial ADC reductions at 3 hours had different evolution of ADC and infarction risks depending on when or if tissue reperfused. These findings provide a physiological basis for the observation that a single ADC measurement at a fixed time after stroke onset may not accurately predict tissue outcome.
authors: Department of Radiology and Biomedical Research Imaging Center, CB# 7513, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
authors: Hongyu
authors: H
authors: An
authors: Andria L
authors: AL
authors: Ford
authors: Katie
authors: K
authors: Vo
authors: William J
authors: WJ
authors: Powers
authors: Jin-Moo
authors: JM
authors: Lee
authors: Weili
authors: W
authors: Lin
mesh_terms: D000368:Aged; D002544:Cerebral Infarction / Q000453:epidemiology* / Q000503:physiopathology; D002560:Cerebrovascular Circulation / Q000502:physiology; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D006801:Humans; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D011446:Prospective Studies; D015424:Reperfusion; D012189:Retrospective Studies; D012307:Risk Factors; D020521:Stroke / Q000150:complications* / Q000473:pathology* / Q000503:physiopathology; D013997:Time Factors