How Imaging Tests Help in Diagnosing Nervous System Disorders
Test |
Uses |
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Cerebral angiography (using a catheter) |
To obtain detailed images of blood vessels of the brain, such as the arteries that carry blood from the heart to the brain (carotid and vertebral arteries) Most often done before procedures such as angioplasty, placement of stents, or surgery to repair an aneurysm (a bulge in an artery) |
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Computed tomography (CT), with or without a radiopaque contrast agent (which can be seen on x-rays) |
To identify structural abnormalities (such as abscesses, tumors, and hydrocephalus) in the brain To identify bleeding or evidence of strokes in the brain To identify ruptured or herniated disks in the spine To identify spinal fractures To monitor the effects of radiation therapy on brain cancer or of antibiotics on a brain abscess |
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CT angiography (CTA) with a radiopaque contrast agent |
To obtain detailed images of blood vessels of the brain and identify clots in arteries in people who have had a stroke (CTA has largely replaced cerebral angiography) |
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Doppler ultrasonography of the carotid arteries and the arteries at the base of the brain (transcranial) |
To identify and evaluate narrowing or blockage of arteries in the neck and head and thus assess the risk of stroke Most often done to evaluate people who have had a transient ischemic attack after the attack and over time |
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To identify structural abnormalities (such as abscesses, tumors, and hydrocephalus) in the brain (images of the brain tissue are clearer and more detailed than those provided by CT, but MRI may not be as readily available) |
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Magnetic resonance angiography (MRA) with or without a radiopaque contrast agent |
To evaluate arteries in people who have had a stroke or a transient ischemic attack or in people who may have an aneurysm or arteriovenous malformation (an abnormal connection between arteries and veins) |
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To detect a blood clot in veins of the brain (cerebral venous thrombosis) and to monitor how treatment affects this disorder |
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To identify which areas of the brain are active when a task (such as reading, writing, remembering, calculating, or moving a limb) is done |
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Perfusion-weighted imaging (PWI) MRI |
To estimate how much blood is flowing through a particular area of the brain |
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Diffusion-weighted imaging (DWI) MRI |
To identify very early stroke and to help diagnose Creutzfeld-Jacob disease |
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To distinguish between abscesses, tumors, and strokes |
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To evaluate blood flow and metabolic activity in the brain To provide information about seizure disorders To help identify Alzheimer disease, Parkinson disease, transient ischemic attacks, and strokes Most often done in research studies |