Echo-planar diffusion-weighted MRI in the diagnosis of acute ischemic stroke: characterisation of tissue abnormalities and limitations in the interpretation of imaging findings

Introduction: An accurate diagnosis is frequently difficult in early stroke. Diffusion-weighted (DW) magnetic resonance imaging (MRI) allows visualization of ischemic parenchyma and quantitative assessment of tissue changes before unequivocal abnormalities appear on T2-weighted MRI. Methods: We analyzed 105 MRI examinations of patients with acute stroke (<24 h) with regard to patterns of abnormalities in T2-weighted and DW MRI. Furthermore, we assessed the influence of artifacts related to DW echo-planar single-shot MRI on image interpretation. Results: Depending on the time of patient assessment there were three partly overlapping T2/DW patterns: (1) in the very early phase (≤ 1.5 h after symptom onset) there was no T2 abnormality and no definite abnormality of diffusion; (2) no T2 abnormality and restricted diffusion (1.5-4 h); (3) T2 hyperintensity and restricted diffusion (≥ 3 h). Typical artifacts (susceptibility distortions, N/2 artifact, chemical shift artifact and eddy current artifact) had to be considered when interpreting images. Conclusions: Provided typical artifacts are taken into consideration, echo-planar DW MRI allows a more precise diagnostic assessment in acute stroke. (orig.)