Prediction of Impending Hemorrhagic Transformation in Ischemic Stroke Using Magnetic Resonance Imaging in Rats

Abstract

Background and Purpose—Hemorrhagic transformation (HT) of ischemic brain tissue may occur in stroke patients either spontaneously or after thrombolysis. A method to assess the risk of HT in ischemic tissue after stroke would improve the safety of thrombolytic therapy. As a means of predicting HT, we investigated the role of contrast-enhanced MRI at acute time points in a rat middle cerebral artery occlusion model with reperfusion. Methods—Intraluminal suture occlusion of the middle cerebral artery was used to produce transient ischemia in male Wistar rats (n=11). Reperfusion was performed by withdrawal of the occluding filament after 2 (n=4), 3 (n=6), or 4 (n=1) hours. MRI studies were performed before and after reperfusion with the use of conventional T1-weighted imaging, with and without gadolinium (Gd-DTPA) contrast agent, and T2-weighted imaging. Follow-up MRI and histological studies were obtained at 24 hours. Results—Petechial hemorrhage occurred by 24 hours in 9 of 11 animals. All animals showed br...