Pitfall of Fluid-Attenuated Inversion Recovery (FLAIR) MR Imaging in Acute Stroke—Does Magnetic Field Strength Influence the Tissue Clock?

Excerpt

Experimental models showed that temporal evolution of increasing T2 relaxation time within the first hours after arterial occlusion follows quite linear course [4], while restricted diffusivity within the ischemic lesion already occurs within several minutes after arterial occlusion [5]. Diffusion-weighted imaging (DWI) alone does not allow exact estimation of the age of ischemic lesions within the first 12 h. Therefore, the concept of DWI-FLAIR (fluidattenuated inversion recovery) mismatch was introduced as a reliable predictor for detecting patients with wake up stroke to be within a time window allowing safe and effective thrombolysis [7]. However, there is evidence that in magnetic resonance imaging (MRI) studies performed on a 3 T MR scanner a negative FLAIR has a rather low sensitivity/specificity of 46 %/79 % in allocating patients for tissue plasminogen within the current time window of 4.5 h [1]. …