Principles and Practical Application of Brain MRI in Acute Ischemic Stroke

Abstract

Various pathomechanisms can cause acute ischemic stroke, and the treatment strategy differs according to the stroke mechanism. Therefore, rapid and accurate diagnosis of ischemic stroke is important. Furthermore, in the hyperacute stage, selecting appropriate patients who may benefit from reperfusion therapy is important. Despite several practical issues, multimodal MRI is useful for accurate diagnosis of acute ischemic stroke, for the evaluation of risks and benefits of reperfusion therapy, and finally for patient selection who may benefit from each treatment. The high sensitivity and specificity of diffusion-weighted image (DWI) helps in distinguishing acute ischemic stroke from stroke mimics. Furthermore, the lesion pattern on DWI reflects the underlying pathomechanism. The lesion mismatch between perfusion-weighted image (PWI) and DWI is thought to represent the potential salvageable tissue by reperfusion therapy. Signal changes of fluid-attenuated inversion recovery (FLAIR) image within DWI lesions may be a surrogate marker of tissue clock reflecting infarction age and might indicate the risk of hemorrhage after reperfusion treatment. Clot sign on gradient echo (GRE) image may reflect the nature of clot, and the location, length, and morphology of clot on GRE may provide predictive information on recanalization. Understanding the clinical implication of various findings of each sequences of multimodal MRI and comprehensively incorporating them into therapeutic decision-making may be a reasonable approach for expanding the indication of reperfusion treatment for acute ischemic stroke patients.