Combined X-ray angiography and diffusion-perfusion MRI for studying stroke evolution after rt-PA treatment in rats

Clinical studies on rt-PA (recombinant tissue-type plasminogen activator) treatment of stroke showed a favorable outcome. However, there are reports of harmful effects of t-PA via the potentiation of excitotoxic injury. We used combined X-ray angiography and MRI imaging to study the balance between the beneficial effect of reperfusion and secondary detrimental effects of rt-PA. Therefore, rats (n=15) were assigned to three groups according to recanalization or lack thereof of the middle cerebral artery (MCA) and rt-PA or saline treatment in an embolic stroke model. Diffusion and perfusion MRI showed that animals had significantly improved perfusion values and final infarct size when recanalization was successful. However, final infarct volumes at 6 h post stroke onset were greater in the rt-PA group compared to controls at comparable perfusion values when the MCA did not recanalize after treatment (67.4+/-5.4 versus 47.7+/-17.9% of ipsilateral hemisphere, P=0.042). Our results demonstrate that the combination of angiography and MR-imaging is useful to further evaluate rt-PA treatment of thromboembolic stroke.