Value of low-field diffusion-weighted MR in acute phase of ischemic stroke

Early detection of ischemic changes in the brain is significant for prompt initiation of suitable, especially thrombolytic, treatment. Until recently, the essential diagnostic method was computerized tomography (CT), despite its limited value in detecting and assessing ischemic area extent. CT perfusion, magnetic resonance (MR) perfusion, and diffusion MR (DWI, diffusion weighted imaging) are currently considered the most sensitive methods. Until recently, DWI was available only in modern, high-field MR units (1.5 -3 Tesla). The aim of our study was to evaluate the usefulness of low-field DWI performed with a modern low-field MR system (with appropriate software) in patients with early ischemic stroke. Forty patients with clinically diagnosed ischemic stroke were examined 1 - 12 hours after onset of symptoms. In all patients, non-contrast CT followed by DWI was performed. The time between both studies did not exceed 30 minutes. After 2 weeks, follow-up MR (FLAIR, T2 and T1-weighted images) was performed in 36 patients. Foci of increased signal intensity, localized in the cerebral hemispheres and posterior fossa, were detected on the DWI images of 30 patients. Follow-up MR studies confirmed ischemic lesions in 24 cases. Among the 10 patients in whom ischemic changes had not been diagnosed in DWI examination, the follow-up MR revealed such in 4 cases. The sensitivity, specificity, and accuracy of DWI were calculated as 87.5%, 50% and 78%, respectively. DWI examination with a low-field MR system enables efficient detection of brain lesions in the early stage of ischemic stroke. (author)