Advantages of adding diffusion-weighted magnetic resonance imaging to conventional magnetic resonance imaging for evaluating acute stroke

Background: Accurate localization of acute ischemic lesions in patients wit h an acute stroke may aid in understanding the etiology of their stroke and ma) improve the management of these patients. Objective: To determine the field of adding diffusion-weighted magnetic res onance imaging (DWI) to a conventional magnetic resonance imaging (MRI) pro tocol for acute stroke. Design: A prospective cohort study. Setting: A referral center. Patients and Methods: Fifty-two patients with a clinical diagnosis of acute stroke who presented within 48 hours after symptom onset were included. An MRI scan was obtained within 48 hours after symptom onset. A neuroradiolog ist (A.M.N.) and a stroke neurologist (G.W.A.) independently identified sus pected acute ischemic lesions on MRI sequences in the following order: (1) T2-weighted and proton density-weighted images, (2) fluid-attenuated invers ion recovery images, and (3) diffusion-weighted images and apparent diffusi on coefficient maps. Main Outcome Measures: Diagnostic yield and interrater reliability for the identification of acute lesions, and confidence and conspicuity ratings of acute lesions for different MRI sequences. Results: Conventional MRI correctly identified at least one acute lesion in 71% (34/48) to 80% (39/49) of patients who had an acute stroke, with the a ddition of DWI, this percentage increased to 94% (46/49) (P<.001). Conventi onal MRI showed only moderate sensitivity (50%-60%) and specificity (49%-69 %) compared with a "criterion standard." Based on the diffusion-weighted se quence, interrater reliability for identifying acute lesions was moderate f or conventional MRI (kappa=0.5-0.6) and good for DWI (kappa=0.8). The obser vers' confidence with which lesions were rated as acute and the lesion cons picuity was significantly (P<.01) higher for DWI than for conventional MRI. Conclusion: During the first 48 hours after symptom onset, the addition of DWI to conventional MRI improves the accuracy of identifying acute ischemic brain lesions in patients who experienced a stroke.