[Diffusion/perfusion MRI study on cerebral ischemia in a rat embolism model].

To determine whether intracerebral distribution of clot emboli can induce perfusion deficits and ischemic brain injury in a rat embolism model, diffusion/perfusion magnetic resonance imaging techniques were employed using a 4.7 Tesla imager. Clot emboli produced from venous blood were injected into the right internal carotid artery of male Sprague-Dawley rats. Diffusion-weighted spin-echo imaging was used to detect early ischemic injuries due to cytotoxic edema every 30 minutes. Sequential echo-planar imaging (EPI), as a form of perfusion imaging, was carried out following bolus i.v. injection of the magnetic susceptibility contrast agent Dy DTPA-BMA. Images (EPI) were also made during clot embolization to localize the distribution of the emboli. The images obtained showed signal loss in the right hemisphere corresponding to the distribution of the emboli result of the magnetic susceptibility effect of deoxyhemoglobin. The spatial distribution of the signal loss corresponded to the perfusion deficits, decreased ADC (apparent diffusion coefficient) areas on diffusion images, and histological abnormalities on TTC-stained specimens. After intra-arterial streptokinase infusion following clot embolization, decreased perfusion deficits and abnormal ADC areas were monitored by diffusion/perfusion MRI. Diffusion/perfusion MR imaging thus provided excellent in vivo mapping of the distribution of the emboli in relation to cerebral perfusion deficits and acute ischemic injury in the rat embolism model.