title: Reduction of Diffusion-Weighted Imaging Contrast of Acute Ischemic Stroke at Short Diffusion Times.
abstract: OBJECTIVE
  Diffusion-weighted imaging (DWI) of tissue water is a sensitive and specific indicator of acute brain ischemia, where reductions of the diffusion of tissue water are observed acutely in the stroke lesion core. Although these diffusion changes have been long attributed to cell swelling, the precise nature of the biophysical mechanisms remains uncertain.
  
  
  METHODS
  The potential cause of diffusion reductions after stroke was investigated using an advanced DWI technique, oscillating gradient spin-echo DWI, that enables much shorter diffusion times and can improve specificity for alterations of structure at the micron level.
  
  
  RESULTS
  Diffusion measurements in the white matter lesions of patients with acute ischemic stroke were reduced by only 8% using oscillating gradient spin-echo DWI, in contrast to a 37% decrease using standard DWI. Neurite beading has recently been proposed as a mechanism for the diffusion changes after ischemic stroke with some ex vivo evidence. To explore whether beading could cause such differential results, simulations of beaded cylinders and axonal swelling were performed, yielding good agreement with experiment.
  
  
  CONCLUSIONS
  Short diffusion times result in dramatically reduced diffusion contrast of human stroke. Simulations implicate a combination of neuronal beading and axonal swelling as the key structural changes leading to the reduced apparent diffusion coefficient after stroke.
authors.affiliation: From the Department of Biomedical Engineering (C.A.B., C.B.), Department of Neurology (M.K., L.G., K.B.), and Department of Radiology (D.E.), Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada; and Department of Neurosurgery, Medical College of Wisconsin, Milwaukee (M.B.).
authors.forename: Corey Allan
authors.initials: CA
authors.lastname: Baron
authors.affiliation: From the Department of Biomedical Engineering (C.A.B., C.B.), Department of Neurology (M.K., L.G., K.B.), and Department of Radiology (D.E.), Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada; and Department of Neurosurgery, Medical College of Wisconsin, Milwaukee (M.B.).
authors.forename: Mahesh
authors.initials: M
authors.lastname: Kate
authors.affiliation: From the Department of Biomedical Engineering (C.A.B., C.B.), Department of Neurology (M.K., L.G., K.B.), and Department of Radiology (D.E.), Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada; and Department of Neurosurgery, Medical College of Wisconsin, Milwaukee (M.B.).
authors.forename: Laura
authors.initials: L
authors.lastname: Gioia
authors.affiliation: From the Department of Biomedical Engineering (C.A.B., C.B.), Department of Neurology (M.K., L.G., K.B.), and Department of Radiology (D.E.), Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada; and Department of Neurosurgery, Medical College of Wisconsin, Milwaukee (M.B.).
authors.forename: Kenneth
authors.initials: K
authors.lastname: Butcher
authors.affiliation: From the Department of Biomedical Engineering (C.A.B., C.B.), Department of Neurology (M.K., L.G., K.B.), and Department of Radiology (D.E.), Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada; and Department of Neurosurgery, Medical College of Wisconsin, Milwaukee (M.B.).
authors.forename: Derek
authors.initials: D
authors.lastname: Emery
authors.affiliation: From the Department of Biomedical Engineering (C.A.B., C.B.), Department of Neurology (M.K., L.G., K.B.), and Department of Radiology (D.E.), Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada; and Department of Neurosurgery, Medical College of Wisconsin, Milwaukee (M.B.).
authors.forename: Matthew
authors.initials: M
authors.lastname: Budde
authors.affiliation: From the Department of Biomedical Engineering (C.A.B., C.B.), Department of Neurology (M.K., L.G., K.B.), and Department of Radiology (D.E.), Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada; and Department of Neurosurgery, Medical College of Wisconsin, Milwaukee (M.B.). christian.beaulieu@ualberta.ca.
authors.forename: Christian
authors.initials: C
authors.lastname: Beaulieu
mesh_terms: D000328:Adult; D000368:Aged; D002545:Brain Ischemia / Q000175:diagnosis* / Q000378:metabolism; D004058:Diffusion; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods* / Q000592:standards; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009010:Monte Carlo Method; D020521:Stroke / Q000175:diagnosis* / Q000378:metabolism; D013997:Time Factors
keywords: diffusion; diffusion tensor imaging; humans; ischemia; stroke