The relationship between magnetic resonance diffusion imaging and autoradiographic markers of cerebral blood flow and hypoxia in an animal stroke model

This study examined the relationship between magnetic resonance diffusion i maging and autoradiographic markers of cerebral blood flow (Tc-99m-hexameth ylpropylene amine oxime) and cerebral hypoxia (I-125-iodoazomycin arabinosi de) in a rat model of stroke. Middle cerebral artery occlusion in the rat w as performed using an intraluminal suture approach. Diffusion, hypoxia, and blood flow maps were acquired 2 hr following occlusion, and were compared with T2 images and histology at 7 hr, Two hours following middle cerebral a rtery occlusion the lesion distributions from the diffusion maps and hypoxi c autoradiographs were similar. The blood flow threshold for increased upta ke of the hypoxic marker was approximately 34 +/- 7% of the normal flow. Th e combination of diffusion or hypoxic images with perfusion maps allowed di fferentiation between four regions: 1) normal tissue; 2) a region of decrea sed perfusion but normal diffusion and normal uptake of hypoxic marker; 3) a region of decreased perfusion, decreased diffusion and increased uptake o f hypoxic marker; 4) a region of decreased perfusion, decreased diffusion a nd low uptake of hypoxic marker. The areas for increased uptake of hypoxic marker and decreased diffusion are equivalent, indicating similar blood flo w thresholds. Regions of oligaemic misery perfusion, ischaemic misery perfu sion and lesion core may be delineated with the combination of diffusion or hypoxic images and perfusion maps. (C) 1999 Wiley-Liss, Inc.