What is a brain MRI?
A brain MRI (magnetic resonance imaging) scan, also called a head MRI, is a painless procedure that produces very clear images of the structures inside of your head — mainly, your brain. MRI uses a large magnet, radio waves and a computer to produce these detailed images. It doesn’t use radiation.
What is a brain MRI with contrast?
Some brain MRI exams use an injection of contrast material. The contrast agent is often gadolinium, which is a rare earth metal. When this substance is present in your body, it alters the magnetic properties of nearby water molecules, which enhances the quality of the images. This improves the sensitivity and specificity of the diagnostic images.
Contrast material enhances the visibility of the following:
- Certain organs’ blood supply.
- Blood vessels.
The contrast can also help diagnose multiple sclerosis, stroke, dementia and infection.
If your brain MRI requires a contrast material, your healthcare provider will insert an intravenous catheter (IV line) into a vein in your hand or arm. They’ll use this IV to inject the contrast material.
Contrast materials are safe intravenous (IV) drugs. Side effects, ranging from mild to severe, do occur, but severe reactions are very rare.
What is the difference between a head MRI and a brain MRI?
A head MRI and a brain MRI are the same procedure. They both provide images of the inside of your head. While healthcare providers most often use head and brain MRIs to assess your brain, these imaging procedures provide images of other structures in your head, too, such as facial bones, blood vessels and nerves.
What does a brain MRI show?
A brain or head MRI shows the structures inside of your head, including:
- Your brain.
- Blood vessels that connect to your brain.
- Your skull and facial bones.
- Structures in your inner ear.
- Your eyes and their supporting tissues, such as your optic nerves.
- Other nerves (large nerves in your head, called cranial nerves).
- Surrounding soft tissues and skull-based structures, such as fat, bones, muscle and connective tissue.
More specifically, a brain or head MRI can show if there are any abnormalities in your brain or the surrounding tissues, including, but not limited to:
- Inflammation and swelling.
- Structural issues.
- Abnormal growths or masses.
- Fluid leaks.
- Hemorrhage (bleeding inside your brain).
- White matter disease.
Why would a neurologist order an MRI of the brain?
Neurologists and other healthcare providers order brain MRIs for several different reasons, including helping diagnose new neurological conditions based on certain symptoms or to monitor existing conditions.
Some of the conditions a brain MRI can help diagnose or monitor include:
- A blood clot in your brain.
- Brain aneurysm.
- Brain hemorrhage.
- Brain infections (encephalitis).
- Brain damage associated with epilepsy.
- Brain tumors and cysts.
- Certain chronic neurological conditions, such as multiple sclerosis (MS).
- Pituitary gland issues, such as a pituitary adenoma.
- Issues with brain development or structure, such as Chiari malformation, and malformations of cortical development. (The term “cortical” refers to the outer layer of your cerebrum.)
- Traumatic brain injury (TBI).
Your healthcare provider may also order an MRI of your head if you have any combination of the following signs and symptoms:
- Migraines and/or chronic headaches.
- Vertigo and frequent episodes of severe dizziness.
- Hearing loss with an unexplainable cause.
- Vision issues not explained by an eye exam.
- Hormonal imbalances related to your hypothalamus and/or pituitary gland.
- Significant changes to your thinking and behavior
- Extreme weakness and fatigue.
Healthcare providers also use brain and head MRI scans before surgeries involving your head to better prepare for the surgery. They also use these scans to ensure that healing from the surgery is going well. Any significant injuries involving your head also prompt healthcare providers to order brain MRI scans to check for injuries, bleeding and swelling.
Who performs a brain MRI?
A radiologist or a radiology technologist will perform your brain (head) MRI. A radiologist is a medical doctor who performs and interprets imaging tests to diagnose conditions. A radiology technologist is a healthcare provider who’s specially trained and certified to perform an MRI scan.
How does a brain MRI work?
Magnetic resonance imaging (MRI) works by passing an electric current through coiled wires to create a temporary magnetic field in your body — in this case, your head. A transmitter/receiver in the machine then sends and receives radio waves. The computer then uses these signals to make digital images of the structures inside of your head, including your brain.
How do I prepare for a brain MRI?
Guidelines about eating and drinking before a brain MRI vary based on the reason for your MRI. Eat and take your medications as usual unless your healthcare provider tells you otherwise.
The magnetic resonance imaging (MRI) scanner uses strong magnets and radio wave signals that can cause heating or possible movement of some metal objects in your head and/or body. This could result in health and safety issues. It could also cause some implanted electronic medical devices to malfunction.
If you have metal-containing objects or implanted medical devices in your body, your healthcare provider needs to know about them before your brain MRI. Certain implanted objects may require additional scheduling arrangements and special instructions. Other items don’t require special instructions but may require an X-ray to check on the exact location of the object before your exam.
It’s important to tell your healthcare provider and MRI technologist if you have any of the following:
- Cardiac pacemaker.
- Middle ear prostheses.
- Cochlear implant.
- A clip used for brain aneurysms.
- Vagal nerve stimulator.
- Metal fragments in your head or within your eyeball.
In addition, tell your healthcare provider if you:
- Are pregnant.
- Aren’t able to lie on your back for 30 to 60 minutes.
- Have claustrophobia (fear of enclosed or narrow spaces).
Leave all jewelry and other accessories at home or remove them before your brain MRI. Metal and electronic items aren’t allowed in the exam room because they can interfere with the magnetic field of the MRI unit, cause burns or become harmful projectiles. These items include:
- Jewelry, watches, credit cards and hearing aids — all of which can be damaged.
- Pins, metal hair accessories, underwire bras and metal zippers, which can distort MRI images.
- Removable dental work, such as dentures.
- Pens, pocketknives and eyeglasses.
- Body piercings.
- Cell phones, electronic watches and tracking devices.
What should I expect during a brain MRI?
Most brain MRI exams are painless, but some people find it uncomfortable to remain still for 30 minutes or longer. Others may experience anxiety due to the closed-in space while in the MRI machine. The machine can also be noisy.
The general steps of a brain MRI scan and what to expect include:
- You’ll change into a hospital gown for the MRI scan.
- You’ll lie face up for most exams on the MRI scanning bed.
- Once you’re lying on the table, the technologist will position a special helmet-like device called a head coil around your head. Some head coils have a mirror attached to them that allows you to see outside of the scanning machine or a small screen that allows you to watch television. This can help prevent feelings of claustrophobia.
- The technologist will then slide you and the scanning bed into the MRI machine.
- As the MRI scan begins, you’ll hear the equipment making a variety of loud knocking and clicking sounds while it’s taking the images. Each series of sounds may last for several minutes. You’ll be given earplugs or headphones to wear to protect your hearing before the procedure begins. You may also be able to listen to music through the headphones.
- It’s important to be very still during the exam to ensure the best quality of images.
- It’s normal for the area of your body being imaged to feel slightly warm. If it bothers you, tell the radiologist or technologist.
- The MRI technologist will be able to see you and can talk with you at all times. An intercom system allows two-way communication while you’re inside the scanner. You’ll also have a call button in your hand that you can push to let the technologist know if you’re having any problems or concerns.
In some cases, your MRI may require contrast. If this applies to you, your healthcare provider will give you an IV injection of contrast material before you undergo the MRI. The IV needle may cause some discomfort but this won’t last long. You may have some bruising afterward. Some people experience a temporary metallic taste in their mouth after the contrast injection.
If you have claustrophobia, your healthcare provider may recommend a sedative drug so you feel more relaxed during the exam, or even anesthesia.
Does your whole body go into the machine for a brain MRI?
In most cases, your whole body won’t go into the MRI machine tunnel if you’re only getting a head or brain MRI.
How long does a brain MRI take?
A brain MRI can take about 30 minutes to an hour to complete. It may take longer if you’re getting a brain MRI with contrast.
Your healthcare provider will be able to give you a more exact time range based on the specific reason for your scan.
Results and Follow-Up
When should I know the results of the test?
After your MRI scan, a radiologist will analyze the images. The radiologist will send a signed report to your primary healthcare provider, who will share the results with you. The report is usually ready for your healthcare provider within one or two days.
You may need a follow-up exam. If so, your healthcare provider will explain why.
A note from Cleveland Clinic
Brain magnetic resonance imaging (MRI) is a very useful and generally safe imaging test that healthcare providers use for a variety of reasons. If you need a brain MRI scan and are worried about the exam or have questions about it, don’t hesitate to ask your healthcare provider. They’re available to answer your questions and support you.
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