title: Correlation of apparent diffusion coefficient and computed tomography density in acute ischemic stroke.
abstract: OBJECTIVE
  Diffusion-weighted MR imaging is very sensitive for the detection of restricted molecular water diffusion in acute ischemic stroke. CT is sensitive to net water uptake in ischemic edema. We compared the decrease in the apparent diffusion coefficient (ADC) in diffusion-weighted MR imaging with CT density changes to study the correlation between diffusion restriction and water uptake in acute stroke patients.
  
  
  METHODS
  Twenty-five patients with acute ischemic stroke of the anterior cerebral circulation underwent MR and CT imaging 1.3 to 5.4 hours after symptom onset. ADC and CT data were transferred into a common 3-dimensional space, and regions of decreased ADC (dADC) were superimposed onto the corresponding CT. Mean values of ADC and Hounsfield units (HU) were determined in comparison with the nonaffected hemisphere.
  
  
  RESULTS
  Mean decrease in ADC (dADC) was 170+/-53x 10(-6) mm2/s and corresponded to a decrease (dCT) in CT density of 1.3+/-0.7 HU. dCT showed a continuous linear decrease of 0.4 HU/h (r=0.55, P<0.01), whereas the decrease is ADC was almost complete after 1.5 hours. A correlation between the decrease in ADC and dCT was found (r=0.41, P=0.04).
  
  
  CONCLUSIONS
  The severity of diffusion restriction correlates with net water uptake in acute ischemic stroke. However, the underlying pathophysiology and different time courses indicate a common reason rather than a direct causality for both phenomena. The time delay and low value of CT density changes provide a reasonable explanation for the higher sensitivity of MR imaging in ischemic stroke.
authors.affiliation: Department of Neuroradiology, University-Hospital Hamburg Eppendorf, Hamburg, Germany. kucinski@ uke.uni-hanburg.de
authors.forename: Thomas
authors.initials: T
authors.lastname: Kucinski
authors.forename: Ole
authors.initials: O
authors.lastname: Väterlein
authors.forename: Volkmar
authors.initials: V
authors.lastname: Glauche
authors.forename: Jens
authors.initials: J
authors.lastname: Fiehler
authors.forename: Ernst
authors.initials: E
authors.lastname: Klotz
authors.forename: Bernd
authors.initials: B
authors.lastname: Eckert
authors.forename: Christoph
authors.initials: C
authors.lastname: Koch
authors.forename: Joachim
authors.initials: J
authors.lastname: Röther
authors.forename: Hermann
authors.initials: H
authors.lastname: Zeumer
mesh_terms: D000208:Acute Disease; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001929:Brain Edema / Q000175:diagnosis* / Q000209:etiology / Q000378:metabolism; D002545:Brain Ischemia / Q000150:complications / Q000175:diagnosis* / Q000378:metabolism; D003710:Demography; D004058:Diffusion; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D020521:Stroke / Q000150:complications / Q000175:diagnosis* / Q000378:metabolism; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D014867:Water / Q000378:metabolism
chemical_list: D014867:Water