title: White matter ischemic changes in hyperacute ischemic stroke: voxel-based analysis using diffusion tensor imaging and MR perfusion.
abstract: OBJECTIVE
  The purpose of this study was to evaluate changes in fractional anisotropy (FA), as measured by diffusion tensor imaging, of white matter (WM) infarction and hypoperfusion in patients with acute ischemic stroke using a quantitative voxel-based analysis.
  
  
  METHODS
  In this prospective study, diffusion tensor imaging and dynamic susceptibility contrast perfusion sequences were acquired in 21 patients with acute ischemic stroke who presented within 6 hours of symptom onset. The coregistered FA, apparent diffusion coefficient, and dynamic susceptibility contrast time to maximum (Tmax) maps were used for voxel-based quantification using a region of interest approach in the ipsilateral affected side and in the homologous contralateral WM. The regions of WM infarction versus hypoperfusion were segmented using a threshold method. Data were analyzed by regression and ANOVA.
  
  
  RESULTS
  There was an overall significant mean difference (P<0.001) for the apparent diffusion coefficient, Tmax, and FA values between the normal, hypoperfused, and infarcted WM. The mean±SD of FA was significantly higher (P<0.001) in hypoperfused WM (0.397±0.019) and lower (P<0.001) in infarcted WM (0.313±0.037) when compared with normal WM (0.360±0.020). Regression tree analysis of hypoperfused WM showed the largest mean FA difference at Tmax above versus below 5.4 s with a mean difference of 0.033 (P=0.0096).
  
  
  CONCLUSIONS
  Diffusion tensor imaging-FA was decreased in regions of WM infarction and increased in hypoperfused WM in patients with hyperacute acute ischemic stroke. The significantly increased FA values in the hypoperfused WM with Tmax≥5.4 s are suggestive of early ischemic microstructural changes.
authors.affiliation: From the Departments of Medical Imaging (K.N., T.P.T., E.A.K., C.S.K.), Biomedical Engineering (T.P.T., S.R.L., E.A.K.), Neurology (C.S.K.), University of Arizona, Tucson; and Department of Radiology, University of California, Los Angeles (N.S.). Kambiznael@gmail.com.
authors.forename: Kambiz
authors.initials: K
authors.lastname: Nael
authors.affiliation: From the Departments of Medical Imaging (K.N., T.P.T., E.A.K., C.S.K.), Biomedical Engineering (T.P.T., S.R.L., E.A.K.), Neurology (C.S.K.), University of Arizona, Tucson; and Department of Radiology, University of California, Los Angeles (N.S.).
authors.forename: Theodore P
authors.initials: TP
authors.lastname: Trouard
authors.affiliation: From the Departments of Medical Imaging (K.N., T.P.T., E.A.K., C.S.K.), Biomedical Engineering (T.P.T., S.R.L., E.A.K.), Neurology (C.S.K.), University of Arizona, Tucson; and Department of Radiology, University of California, Los Angeles (N.S.).
authors.forename: Scott R
authors.initials: SR
authors.lastname: Lafleur
authors.affiliation: From the Departments of Medical Imaging (K.N., T.P.T., E.A.K., C.S.K.), Biomedical Engineering (T.P.T., S.R.L., E.A.K.), Neurology (C.S.K.), University of Arizona, Tucson; and Department of Radiology, University of California, Los Angeles (N.S.).
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Krupinski
authors.affiliation: From the Departments of Medical Imaging (K.N., T.P.T., E.A.K., C.S.K.), Biomedical Engineering (T.P.T., S.R.L., E.A.K.), Neurology (C.S.K.), University of Arizona, Tucson; and Department of Radiology, University of California, Los Angeles (N.S.).
authors.forename: Noriko
authors.initials: N
authors.lastname: Salamon
authors.affiliation: From the Departments of Medical Imaging (K.N., T.P.T., E.A.K., C.S.K.), Biomedical Engineering (T.P.T., S.R.L., E.A.K.), Neurology (C.S.K.), University of Arizona, Tucson; and Department of Radiology, University of California, Los Angeles (N.S.).
authors.forename: Chelsea S
authors.initials: CS
authors.lastname: Kidwell
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002545:Brain Ischemia / Q000175:diagnosis* / Q000378:metabolism; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods* / Q000592:standards; D056324:Diffusion Tensor Imaging / Q000379:methods* / Q000592:standards; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D020521:Stroke / Q000175:diagnosis* / Q000378:metabolism; D066127:White Matter / Q000378:metabolism / Q000473:pathology*
keywords: diffusion imaging; ischemia; magnetic resonance imaging; perfusion imaging; stroke