How can magnetic resonance imaging (MRI) help diagnose stroke?

Magnetic resonance imaging (MRI) uses a powerful magnetic field to take highly detailed pictures of soft tissues such as the brain and heart. Subtle variations show up clearly, so that an ischemic stroke, tumor, or blood clot is visible against the surrounding healthy tissue. MRI can document the extent and location of an ischemic stroke deep inside the brain within minutes of its onset. It can precisely distinguish infarcted (permanently damaged) brain from blood-starved brain at risk of infarction (death of an area of tissue from lack of oxygen). It can also detect intracerebral bleeding, although most physicians prefer to get this information from CT scans (or CT angiography [CTA] scans, if they are available) because they're quicker and easier to do.