Comparison of Perfusion- and Diffusion-weighted MRI in Acute Ischemic Stroke

ABSTRACT

BACKGROUND: Perfusion imaging (PI) of magnetic resonance imaging (MRI) uses the signal loss that occurs during dynamic tracking of the first pass of intravenous paramagnetic contrast agent. Then different hemodynamic measurements can be calculated and displayed as perfusion maps. Diffusion-weighted imaging (DWI) measures diffusional movement of water molecules within the brain and it can identify acute ischemic injury or cytotoxic edema. We evaluated clinical usefulness of PI and DWI in acute ischemic stroke. METHODS: Fifteen patients with clinical diagnosis of acute cerebral infarction were imaged with PI, DWI, and magnetic resonance angiogram (MRA) including FLAIR within 24 hours after onset. Comparisons were made between infarct volumes measured by DWI and PI using the parameters including relative mean transit time (rMTT) map, relative cerebral blood volume (rCBV) map, and relative cerebral blood flow (rCBF) map. RESULTS: Two patterns were found. rMTT map in PI lesion is larger than in the DWI lesion (n=7/15), and rMTT map in PI lesion is the same size or smaller than in DWI lesion (n=8/15). The former pattern was shown in cases with severe stenosis or occlusion of the major cerebral artery (MCA, PCA, or ICA) on MRA. The majority of latter pattern was lacunes (n=6/8). Also, we found presence of infarction cores surrounded by hypoperfused areas in rMTT map in acute largearterial territorial infarction. CONCLUSIONS: Perfusion- and Diffusion- weighted MRIs may be useful in differentiating large-arterial territorial infarction from lacunes.