Combined Diffusion and Perfusion MRI With Correlation to Single-Photon Emission CT in Acute Ischemic Stroke: Ischemic Penumbra Predicts Infarct Growth

Abstract

Background and Purpose —More effective imaging methods are needed to overcome the limitations of CT in the investigation of treatments for acute ischemic stroke. Diffusion-weighted MRI (DWI) is sensitive in detecting infarcted brain tissue, whereas perfusion-weighted MRI (PWI) can detect brain perfusion in the same imaging session. Combining these methods may help in identifying the ischemic penumbra, which is an important concept in the hemodynamics of acute stroke. The purpose of this study was to determine whether combined DWI and PWI in acute (<24 hours) ischemic stroke can predict infarct growth and final size. Methods —Forty-six patients with acute ischemic stroke underwent DWI and PWI on days 1, 2, and 8. No patient received thrombolysis. Twenty-three patients underwent single-photon emission CT in the acute phase. Lesion volumes were measured from DWI, SPECT, and maps of relative cerebral blood flow calculated from PWI. Results —The mean volume of infarcted tissue detected by DWI increased from 46.1 to 75.6 cm 3 between days 1 and 2 ( P <0.001; n=46) and to 78.5 cm 3 after 1 week ( P <0.001; n=42). The perfusion-diffusion mismatch correlated with infarct growth ( r =0.699, P <0.001). The volume of hypoperfusion on the initial PWI correlated with final infarct size ( r =0.827, P <0.001). The hypoperfusion volumes detected by PWI and SPECT correlated significantly ( r =0.824, P <0.001). Conclusions —Combined DWI and PWI can predict infarct enlargement in acute stroke. PWI can detect hypoperfused brain tissue in good agreement with SPECT in acute stroke.