Researchers use brain scans to study brain development in healthy people and people with illnesses. This publication answers frequently asked questions about what brain scans can and cannot do related to diagnosing mental illnesses.
Brain imaging scans, also called neuroimaging scans, are being used more and more to help detect and diagnose a number of medical disorders and illnesses. Currently, the main use of brain scans for mental disorders is in research studies to learn more about the disorders. Brain scans alone cannot be used to diagnose a mental disorder, such as autism, anxiety, depression, schizophrenia, or bipolar disorder.
In some cases, a brain scan might be used to rule out other medical illnesses, such as a tumor, that could cause symptoms similar to a mental disorder, such as depression. Other types of tests are needed for a mental illness to be properly diagnosed. Scientists are studying differences in the brains of people with and without a mental illness to learn more about these disorders. However, at this time relying on brain scans alone cannot accurately diagnose a mental illness or tell you your risk of getting a mental illness in the future.
Some types of brain scans pose health risks due to the radiation they use to create a picture of the brain. Because of these risks, brain scans should not be used if you don't need them. In addition, these scans are very expensive, and unless your doctor prescribes such a test, they may not be fully covered by health insurance.
What Brain Scans Can Do
- Show damage to brain tissue, the skull, or blood vessels in the brain
- Be used with other medical tests to help doctors find the right diagnosis for mood and behavioral problems
- Help researchers study healthy brain development, effects of mental illnesses or effects of mental health treatments on the brain.
What Brain Scans Cannot Do
- Diagnose mental illness when used by themselves
- Predict risk of getting a mental illness.
Frequently Asked Questions about Brain Scans
Q. Can a brain scan tell me what mental disorders I have or might get?
A. No scientific studies to date have shown that a brain scan by itself can be used for diagnosing a mental illness or to learn about a person's risk for disease. Researchers use brain scans to study brain development in healthy people and people with illnesses, disease progression, and the effects of medications or other treatments on the brain.
In practice, when used with other types of medical tests and done by an experienced doctor, brain scans can be used to confirm a diagnosis of a small number of disorders, such as brain tumors, where there is obvious damage in the brain. Brain scans are not usually the first test a doctor would do to diagnose changes in mood and behavior. Other medical tests a doctor may use include behavioral and cognitive tests or a medical interview.
Researcher analyzes FMRI brain images
Q. Should I have a brain imaging scan?
A. When used with other medical tests, they can provide useful information about:
- Brain tumors, infections, and other brain diseases
- Bleeding, blood clots, or other signs of stroke
- Skull fractures or brain damage from head injuries
- Diseases or disorders affecting the skull or blood vessels in the brain.
Q. What types of brain scans, or neuroimaging tests, are there?
A. There are two main types of neuroimaging tests: structural and functional.
- Structural imaging creates a "snapshot" of the brain's structure, including bone, tissue, blood vessels, tumors, infection, damage, or bleeding such as from a stroke.
- Functional imaging reveals the brain's ever-changing activity and chemistry by measuring the rate of blood flow, chemical activity, and electrical impulses in the brain during specific tasks.
Patient enters PET scan machine.
Q. Are there risks associated with brain scans?
A. Brain scans are relatively safe and do not cause any pain. However, risks include exposure to magnetic fields and radiation. Safety measures are used to limit these risks such as using the lowest possible radiation or magnetic level to do the scan.
Children and teens may be more sensitive to these risks. If your child needs a brain scan, ask if there are special precautions you can take or whether a different type of brain scan can be used. Ask the doctor doing the scan if the machine's settings have been adjusted for a child.
Women who are pregnant or breastfeeding should also talk with their doctor about how to prepare for any type of brain scan. While most types of scans pose little risk to the developing fetus, the doctor may make different recommendations to accommodate pregnancy.
Another possible risk is claustrophobia, or a fear of small spaces. Many brain scanning machines look like large tubes or giant "donuts" that are open on both ends. The machines can be very loud while scanning takes place. Some people feel scared or nervous when inside the machines. Sometimes, an injury or other medical condition can make it uncomfortable or painful for a person to hold a certain position.
It is important to stay still in order to get a clear picture. Tell your doctor if you are afraid of being inside the brain scanning machine or think you cannot stay still for any other reason. The doctor can give you a sedative to help you lie still, or may suggest a different type of test entirely.
Talk with your doctor to make sure you understand the possible risks and benefits before deciding to get a brain scan. In general, a person should not need more than one of the same type of brain scan. If a doctor recommends a brain scan that you've already done in the past, ask if you really need to get the test repeated.
Patient in MEG scanner
Q. What can research using brain imaging technologies tell us about disease risk?
A. As they continue to learn more about how the healthy brain develops and which processes may contribute to specific diseases, scientists are building a more complete picture of how to detect which people are at risk of common diseases.
This research also is helping to reveal biological pathways that guide thoughts and emotions, and how experiences, medications, or environmental substances affect the brain. Scientists can use this information to design better screening and prevention for specific disorders, and improve on the delivery and effectiveness of mental health treatments.
Technician checks MRI machine.
|Risk from magnetic fields:*||Risk from radiation:|
|These scans use strong magnets to develop pictures of the brain. This means that a person must remove all jewelry, piercings, and clothing with metal before entering the scanning machine.|
Medication patches, such as nicotine patches or ones that release hormones, sometimes contain metal in the sticky backing, which can burn the skin if worn during an MRI. If you use such patches, talk to your doctor about if and when you should remove them.
It's important to tell your doctor if you have any metal in your body, such as metal braces or metal fillings in your teeth, embedded bullets, shrapnel, or implanted medical devices - pacemakers, aneurysm clips, medication pumps, metal plates, screws, or pins.
If located close to the head, they may distort the scanned image. Sometimes, the strong magnetic field causes these objects to move, which can cause an injury. If you're not sure about your risk, check with the doctor before getting this type of brain scan.
|These scans expose people to low levels of radiation. For example, the amount of radiation from one CT scan of the head is about the same as the amount that the average person receives from natural sources of radiation over eight months.1 Natural sources of radiation include naturally occurring radioactive materials and cosmic rays such as emitted by the sun.|
Also, some people may be allergic to the chemicals, called contrast dyes or tracers, used to make sure brain structures show up in these types of scans. In some cases, these chemicals are radioactive but lose their potency fairly quickly.
If you have ever had a bad reaction to a contrast dye or tracer, tell the doctor before you get the scan. In general, children should not have PET or SPECT scans.
|* Magnetoencephalography (MEG) scanning does not carry these risks because it does not use magnets.||1Computed Tomography (CT) â€” Head.External Link: Please review our disclaimer.. Accessed on June 18, 2008.|
For more detailed descriptions of the different types of brain scans and other tests used to diagnose brain disorders, see the booklet "Neurological Diagnostic Tests and Procedures," distributed by the National Institute on Neurological Disorders and Stroke.
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U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES
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National Institute of Mental Health
NIH Publication No. 09-7460