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In vivo quantification of transvascular water exchange during the acute phase of permanent stroke
Author(s) -
Kim Y.R.,
Tejima E.,
Huang S.,
Atochin D.N.,
Dai G.,
Lo E.H.,
Huang P.L.,
Bogdanov A.,
Rosen B.R.
Publication year - 2008
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.21708
Subject(s) - magnetic resonance imaging , in vivo , medicine , stroke (engine) , blood–brain barrier , ischemia , cortex (anatomy) , middle cerebral artery , pulse (music) , cardiology , nuclear medicine , blood volume , pathology , effective diffusion coefficient , radiology , central nervous system , neuroscience , biology , mechanical engineering , microbiology and biotechnology , electrical engineering , detector , engineering
Abstract Mechanisms that underlie early ischemic damages to the blood‐brain‐barrier (BBB) are not well understood. This study presents a novel magnetic resonance imaging (MRI) technique using a widely available pulse sequence and a long‐circulating intravascular contrast agent to quantify water movements across the BBB at early stages of stroke progression. We characterized the integrity of the BBB by measuring the flip angle dependence of the water exchange‐affected MRI signal intensity, to generate an efficient quantitative index of vascular permeability (WEI, or water exchange index). We performed in vivo MRI experiments to measure the transvascular WEI immediately after the permanent filament occlusion of the middle cerebral artery of mice (n = 5), in which we monitored changes in blood volume (V b ), apparent diffusion coefficient (ADC), and intra‐/extravascular WEI for 4 hours. Statistically significant elevations ( P < 0.05) of WEI in the ischemic tissue were observed as early as 1 hour after ischemic onset. Initial reduction of the apparent blood volume (V app ) in the infarct cortex was followed by a continuous increase of V app over time. Although the measured ADC in the ipsilesional cortex continuously decreased, the abnormally high intra‐/extravascular WEI remained constant at a significantly elevated level, indicating apparent BBB injury at this early stage of stroke. Magn Reson Med 60:813–821, 2008. © 2008 Wiley‐Liss, Inc.

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