Comparison of CT with diffusion-weighted MRI in patients with hyperacute stroke

Tissue changes in ischaemic stroke are detectable by diffusion-weighted MRI (DWI) within minutes of the onset of symptoms. However, in daily routine C T is still the preferred imaging modality for patients with acute stroke. O ur purpose of this study was to determine how early and reliably ischaemic brain infarcts can be identified by CT and DWI. Three neuroradiologists, bl inded to clinical signs but aware that they were dealing with stroke, analy sed the CT and DWI of 31 patients with an acute ischaemic stroke. We calcul ated kappa -values to analyse inter-rater variability. The ratings were com pared with followup studies showing the extent of the infarct. The combined assessment of all observers gave positive findings in 77.4 % of all CT exa minations, with kappa = 0.58. Areas of high signal were seen on all DWI stu dies by all observers (kappa = 1). Estimation of the extent of the infarct based on DWI yielded kappa = 0.70 and that based on CT kappa = 0.39. DWI wa s much more reliable than CT in the detection of early ischaemic lesions an d we believe that it should be used in acute ischaemic stroke before aggres sive therapeutic intervention.