Imaging Devices Used to Identify a Stroke
Stroke Imaging Tests
Physicians use several diagnostic techniques and imaging tools to help diagnose a stroke quickly and accurately. A CT scan or MRI are the two most common. These tests can help determine if a stroke occurred, its location, and whether it is caused by bleeding (hemorrhagic stroke) or lack of oxygen and nutrients (ischemic stroke). They can also be used to exclude other problems that can mimic signs of a stroke, such as a tumor.
The most widely used imaging test to diagnose a stroke is the computed tomography scan, which is also known as a CAT scan, computed axial tomography, or CT scan. A CT scan creates a series of cross-sectional images of the head and brain. CT is the most commonly used diagnostic technique for acute stroke and it also has unique diagnostic benefits. A CT scan can:
- Quickly rule out bleeding
- Occasionally show a tumor that might mimic a stroke
- Show evidence of early damage.
Damage will generally show up on a CT scan about six to eight hours after the start of stroke symptoms.
Another imaging device used to diagnose a stroke is the magnetic resonance imaging scan, or MRI. MRI uses magnetic fields to detect subtle changes in brain tissue content. The benefit of MRI over a CT scan is that it is more accurate and it can make an earlier diagnosis of damage, especially for smaller strokes. A MRI is equally accurate in determining when bleeding is present.
MRI is more sensitive than CT for other types of brain disease, such as brain tumor, that might mimic a stroke. Healthcare providers cannot perform MRIs in cases where patients have certain types of metallic or electronic implants, such as pacemakers for the heart.
Although increasingly used in the emergency diagnosis of stroke, MRI is not immediately available at all hours in most hospitals where CT is used for acute stroke diagnosis. Also, MRI takes longer to perform than CT, and may not be performed if it would significantly delay stroke treatment.