PERFUSION AND DIFFUSION MR-IMAGING OF THROMBOEMBOLIC STROKE

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 suscept ibility-weighted echo-planar images. A signal intensity decrease of 7% +/- 3 in ischemic brain (1% +/- 2 in normal brain) was attributable t o a T2 decrease due to increased blood deoxygenation, which correlate d well with subsequently measured decreases in the apparent diffusion coefficient. The same multisection methods were used to track the firs t-pass transit of a bolus of dysprosium-DTPA-BMA [diethylenetriaminepe ntnacetic acid-bis(methylamide)] to assess relative tissue perfusion b efore and after stroke and after treatment with a thrombolytic agent. Analysis of contrast agent transit profiles suggested a total perfusio n deficit in ischemic tissue and essentially unchanged perfusion in no rmal brain tissue after stroke.