Early Prediction of Gross Hemorrhagic Transformation by Noncontrast Agent MRI Cluster Analysis After Embolic Stroke in Rat

Abstract

Background and Purpose— Our goal was to develop magnetic resonance indices, without image contrast agent enhancement, that predict hemorrhagic transformation (HT) in a rat model of embolic stroke. Methods— Male Wistar rats subjected to embolic stroke with (n=12) or without (n=10) the combination treatment with recombinant tissue plasminogen activator and an anti–platelet glycoprotein IIb/IIIa antibody 7E3 F(ab′) 2 initiated at 4 hours after onset of stroke were investigated using a 7-T MRI system. Radiofrequency saturation T 1 (T 1sat ) maps with magnetization transfer, apparent diffusion coefficient of water (ADC w ) maps in 3 directions, and T 2 maps were measured at 2, 24, and 48 hours after embolization. MRI data were analyzed individually and using 2D cluster plots. Histological measurements were obtained at 48 hours. Results— Gross hemorrhage was detected at 48 hours in 7 (4 control, 3 treated) of 22 animals. The 2D cluster plot using MRI T 1sat and ADC w maps obtained at 2 hours after stroke predicted all gross HT. The location of gross hemorrhage predicted by the 2D cluster plot was within 0.75 mm of the identifying MRI cluster. Conclusions— The 2D MRI cluster plot analysis using T 1sat and ADC w maps acquired at 2 hours after the onset of embolic stroke predicts gross HT.