Corey Allan Baron1, Mahesh Kate1, Laura Gioia1, Kenneth Butcher1, Derek Emery1, Matthew Budde1, Christian Beaulieu2. 1. 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.). 2. 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.
Abstract
BACKGROUND AND PURPOSE: 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.
BACKGROUND AND PURPOSE: 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 humanstroke. 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: M T Berndt; C Maegerlein; T Boeckh-Behrens; S Wunderlich; C Zimmer; S Wirth; F G Mück; S Mönch; B Friedrich; J Kaesmacher Journal: AJNR Am J Neuroradiol Date: 2019-12-19 Impact factor: 3.825