Imaging Tests of the Brain

Evaluating Brain Diseases

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A number of different imaging tests can be used to assess the brain’s structure and function. These tests are used to aid in the diagnosis and treatment planning of conditions that affect the brain. 

Imaging tests can be used to visualize the structure of the brain, skull, or blood vessels. Some diagnostic tests also provide information about activity in different regions of the brain. Interventional procedures for treatment of brain conditions are often done with real time imaging guidance as well. 

Types of Brain Imaging Tests

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X-Ray

Your healthcare provider might order an X-ray of your skull or facial bones if you have had a traumatic head injury. An X-ray is a quick test that does not require injections.

An X-ray can be used to examine the skull and facial bones. This test can identify fractures or major bone problems, such as tumors that invade the bones of the face or skull. 

Computerized Tomography (CT)

A brain CT is often used in emergency situations, such as head trauma or a sudden change of consciousness. This is a relatively fast test that can be done in a few minutes.

A brain CT scan visualizes the structure of the brain and skull, and it can identify blood in and around the brain. A brain CT scan can also identify fluid, swelling, large tumors, or a large stroke. Major structural changes, such as pressure from a tumor pushing on one side of the brain can be detected with a brain CT scan. 

Generally, subtle changes, such as damage to the brain that’s caused by a stroke might not be visible with a brain CT within the first few days, especially if the stroke is small.

Magnetic Resonance Imaging (MRI) 

Your healthcare provider might order a brain MRI if there is a concern that you may have a stroke, inflammation, demyelination, a tumor, or an infection of the brain. 

If you are having a brain MRI, it may take an hour or so. You would lie on a table with your head under a tube that is shaped somewhat like a large donut.

You might have contrast dye injected intravenously (IV, into your vein). This helps define the details and outlines of different structures in the MRI images, such as cancer or an abscess. Most people are able to have this test without any problems, but the feeling of being partially enclosed gives some people a sense of claustrophobia. 

A brain MRI can provide a more detailed picture than a brain CT. It can identify small or large tumors, multiple sclerosis (MS), encephalitis (brain inflammation), or meningitis (inflammation of the meninges that lie between the brain and the skull). A brain MRI can detect brain damage due to a small stroke, often even in the very early stages.

Unlike a brain CT, a brain MRI might not detect blood in the very early stages of a brain bleed.

Angiography 

You might have an angiography if there is a concern about a defect of one or more of the blood vessels in your brain. A variety of angiography methods include CT angiography (CTA), MR angiography (MRA), or an invasive angiography test. Sometimes a therapeutic procedure can be done during an invasive angiography as well.

You would need to have IV contrast when you have an angiography. You can have a brain CTA at the same time as your brain CT or a brain MRA at the same time as your brain MRI. The additional angiography images may prolong the time that you are having the test. 

If you have an invasive brain angiography, you may have contrast dye injected through a catheter. This is a small tube that is inserted into a blood vessel, typically in the groin. Sometimes the catheter is advanced to a blood vessel in the brain for a therapeutic procedure, such as repair of a blood vessel defect. 

Angiography is a test that is done to visualize the blood vessels of the brain. Angiography testing can detect blood clots, tears, defects, and structural abnormalities of the blood vessels in the brain, including brain aneurysms and arteriovenous malformations (AVMs).

Functional Brain MRI (fMRI)

An fMRI test is used to assess brain function and blood flow. This test can detect changes in brain activity. Your fMRI images can change from minute to minute based on the tasks that you are doing.

An fMRI involves an injection of IV dye. It can be used help healthcare providers understand which areas of the brain are involved in various skills, such as when a person is recovering from a stroke.

Sometimes fMRI is used in experimental studies when researchers aim to pinpoint the areas of the brain that are involved in specific functions, like language or memory.

Positron Emission Tomography (PET)

A PET scan of the brain is used to evaluate activity in different areas of the brain. This test can assess some types of brain damage that affect the metabolism (energy use) of the brain. 

You would have a radioactive tracer injected into your vein, and the tracer can help to differentiate the varying levels of activity. The test can take several hours, and it is not considered invasive. 

Sometimes this test is used to evaluate conditions like dementia, movement disorders, or brain tumors.  It may be used to identify the areas that should be targeted in epilepsy surgery. In general, PET scan is not a standard test and it is also used in experimental studies.

Brain Single Photon Emission Tomography (SPECT)

Brain SPECT is a test that can assess brain activity and blood flow. It involves IV injection of radioactive material. This test can take about an hour, and it is typically used in the assessment of epilepsy in preparation for epilepsy surgery.

It may also show changes in brain metabolism in association with conditions like dementia and schizophrenia, although it is not a standard test used in the diagnosis of these conditions.

A Word From Verywell

Brain imaging tests can be useful in the evaluation of many conditions, such as stroke, MS, and meningitis. Each condition can usually be evaluated with only a few different tests, so your healthcare provider would narrow down the possible causes of your symptoms to determine which diagnostic test would be best for you. 

Brain imaging tests are generally safe and are not painful or uncomfortable. Some brain imaging tests are interpreted by healthcare providers who are specialized in reading these types of images, so you might not know the result of your test right away—you may need to wait several days for a definitive reading.

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