PERFUSION AND DIFFUSION-WEIGHTED MR-IMAGING FOR IN-VIVO EVALUATION OFTREATMENT WITH U74389G IN A RAT STROKE MODEL

Background and Purpose The present study was performed to examine the potential of diffusion-weighted (DW) imaging and dynamic first-passage bolus tracking of susceptibility contrast agents (perfusion imaging) for early in vivo evaluation of the effects of treatment with the free radical scavenger U74389G in a rat model of temporary focal ischemia. Methods After 45 minutes of middle cerebral artery occlusion, the tre atment group (n = 9) received an infusion of U74389G, and the control group (n = 9) received the identical volume of the vehicle. Reperfusio n was instituted in both groups after 120 minutes of middle cerebral a rtery occlusion. The DW images were collected during middle cerebral a rtery occlusion and reperfusion and were compared with histologically assessed areas of tissue injury after 2 hours of reperfusion: The dyna mic perfusion series were processed on a pixel-to-pixel basis to produ ce parametric maps reflecting the maximum reduction in the signal obta ined during the first passage of the contrast agent and the time delay between the arrival of the bolus and the point of maximum contrast-ag ent effect.Results The area of ischemic injury, as assessed from the D W imaging at 60 minutes of reperfusion, was significantly smaller in t he treatment group: 9 +/- 8% of ipsilateral hemisphere compared with 1 9 +/- 8% in the control group. The histological examination after 2 ho urs of reperfusion demonstrated an area of ischemic injury of 10 +/- 8 % for the treatment group compared to 25 +/- 10% in the control group. In the treatment group, the perfusion imaging showed a reduction in t ime delay to maximum effect of the contrast agent in the ischemic hemi sphere compared with the control group. Conclusions The DW imaging dur ing early reperfusion showed a protective effect of postocclusion trea tment with the free radical scavenger U74389G. The improvement of time delay to maximum effect of the contrast agent observed in the perfusi on imaging of the treatment group may reflect an improvement in the co llateral flow to the ischemic tissue.