Perfusion and diffusion MR imaging of thromboembolic stroke

Abstract

A carotid embolic stroke model in rats was studied with a combination of diffusion- and perfusion-sensitive magnetic resonance (MR) imaging at 4.7 T. Capillary blood deoxygenation changes were monitored during formation of focal ischemia by acquiring multisection magnetic susceptibility-weighted echo-planar images. A signal intensity decrease of 7% ± 3 in ischemic brain (1% ± 2 in normal brain) was attributable to a T2* decrease due to increased blood deoxygenation, which correlated well with subsequently measured decreases in the apparent diffusion coefficient. The same multisection methods were used to track the first-pass transit of a bolus of dysprosium-DTPA-BMA [diethylenetriaminepentaacetic acid-bis(methylam-ide)] to assess relative tissue perfusion before and after stroke and after treatment with a thrombolytic agent. Analysis of contrast agent transit profiles suggested a total perfusion deficit in ischemic tissue and essentially unchanged perfusion in normal brain tissue after stroke.