From the Guidelines
Diffusion-Weighted Imaging (DWI) MRI is the most sensitive and specific imaging technique for acute ischemic stroke, allowing for early identification of the lesion size, site, and age, and detection of relatively small cortical or subcortical lesions 1.
Key Features of DWI MRI
- High sensitivity (88% to 100%) and specificity (95% to 100%) for detecting acute ischemia 1
- Ability to detect ischemic regions within minutes of symptom onset 1
- Can identify subclinical satellite ischemic lesions and provide information on stroke mechanism 1
- Allows for differentiation of acute from chronic stroke based on temporal evolution of diffusion characteristics 1
Additional MRI Sequences
- Perfusion-Weighted Imaging (PWI): provides relative measures of cerebral hemodynamic status and can help identify the ischemic penumbra 1
- Fluid-Attenuated Inversion Recovery (FLAIR): useful for showing abnormal accumulations of fluid 1
- Gradient-Recalled Echo (GRE): can detect intraparenchymal hemorrhage 1
- Magnetic Resonance Angiography (MRA): demonstrates patency or occlusion of cerebral arteries 1
Clinical Utility
- DWI MRI can provide helpful early prognostic information and guide treatment decisions 1
- Multimodal MRI approaches, including DWI, PWI, and MRA, can provide comprehensive information on acute ischemic stroke and help identify patients who may benefit from thrombolytic therapy or other interventions 1
From the Research
MRI Types Used for Stroke
- Diffusion-weighted MRI (DWI) is used to diagnose acute ischemic stroke, as it is more sensitive than conventional MR sequences in the hyperacute stage 2, 3.
- Perfusion-weighted MRI (PWI) is used in combination with DWI to identify the presence of ischemic penumbra and to evaluate brain tissue at risk of infarction 2, 3.
- MRI angiography is used as a non-invasive and non-ionizing imaging method to detect cerebral arterial occlusion or significant stenosis, and to evaluate actual collateral flow 2, 3.
- MR diffusion-weighted imaging and MR perfusion-weighted imaging are used to find brain tissue at risk and to assess the extent of parenchymal perfusion 3, 4.
Key Features of MRI in Stroke Diagnosis
- MRI allows accurate diagnosis of the infarct lesion and detection of cerebral arterial occlusion or significant stenosis 2.
- MRI can display certain reversible ischemic changes and may be used to identify patients who need thrombolysis 2, 3.
- MRI is a more sensitive modality than CT in diagnosing acute brain ischemia, especially for smaller infarcts 3, 5.