MRI (Magnetic Resonance Imaging)

An MRI (magnetic resonance imaging) scan is an imaging test that produces clear pictures of the inside of your body. MRI uses a large magnet, radio waves and a computer to make these detailed images. It’s especially useful for looking at soft tissues, like muscles, ligaments and nerves. It can help diagnose conditions affecting your brain, spine, joints and organs.

A traditional MRI scanner is a large, tunnel-shaped machine with an opening. You’ll lie on a table that slides into the tunnel while the machine takes images.

Healthcare providers can “look at” several different structures inside your body using MRI, including:

• Your brain and surrounding nerve tissue
• Organs in your chest and abdomen, like your heart, liver, kidneys, spleen, bowel, pancreas and adrenal glands
• Breast tissue
• Your spine and spinal cord
• Pelvic organs, including your bladder and reproductive organs
• Blood vessels

An MRI scan is generally safe and low risk when you follow safety guidelines. Unlike X-rays and CT scans, MRI doesn’t use radiation. The strong magnetic field isn’t harmful, but it can affect implanted medical devices and metal objects. Before the MRI, your provider will ask you about any implants, medical devices or metal in your body to help keep you safe.

What does an MRI show?

Healthcare providers use MRI to help diagnose or monitor the treatment for many different conditions. There are also different types of MRIs based on which area of your body your provider wants to examine.

Brain and spine MRIs can help diagnose:

• Brain and spinal tumors
• Brain aneurysms
• Stroke
• Multiple sclerosis (MS)
• Spine and spinal cord conditions, including injuries and pinched nerves

Functional MRI (fMRI) measures brain activity by tracking changes in blood flow. Providers often use it for brain mapping before surgery.

Heart MRIs (cardiac MRI) can help evaluate:

• Heart structure and function
• Blood flow through your heart and major blood vessels
• Heart damage from coronary artery disease or a heart attack
• Congenital heart disease
• Heart tumors, infections and inflammation

Body MRIs can help diagnose:

• Tumors in your chest, abdomen or pelvis
• Liver, pancreas and bile duct conditions
• Inflammatory bowel diseases
• Blood vessel abnormalities and inflammation

Bone and joint MRIs can help evaluate:

• Bone tumors and infections
• Joint injuries
• Spine and disk problems

Other specialized MRI scans include:

• Your provider may use breast MRIs with mammograms to help detect breast cancer if you’re at high risk for the disease.
• Magnetic resonance angiography (MRA) creates detailed images of blood vessels and can help detect aneurysms, narrowing or blockages.

How does an MRI work?

MRI uses an electric current in coiled wires to create a temporary magnetic field. This magnetic field works with radio waves sent from a transmitter/receiver in the scanner. The radio waves cause certain atoms in your body to produce signals, which the scanner detects. A computer then processes these signals to create detailed digital images of the area being scanned.

What happens during your MRI may be different depending on if you’re having an open MRI or an MRI with contrast.

An open MRI refers to the type of machine that takes the images. Open MRI machines have a more spacious design than traditional MRI machines. This can help people who feel anxious in enclosed spaces (claustrophobia). It’s open on two sides. Some facilities have a stand-up (or upright) MRI scanner. This means you can sit, stand or bend during the test.

MRI with contrast uses a contrast dye to make certain tissues and structures easier to see. Contrast can help highlight tumors, inflammation, blood vessels and blood flow. If your MRI requires contrast, a healthcare provider will inject it into a vein in your arm or hand through an IV. Contrast is generally safe, and serious reactions are rare. Let your provider know if you’re pregnant before getting an MRI with contrast.

What do I need to do to prepare for an MRI?

MRI uses strong magnets and radio wave signals that can interfere with metal objects and implanted devices. If you have metal-containing objects or implanted devices in your body, your healthcare provider needs to know about them before the MRI. This lets them take additional precautions so your test is safe.

Tell your provider and MRI technologist if you have any of the following:

• Heart pacemaker or defibrillator
• Electronic or implanted stimulators or devices
• Metallic joint prostheses
• Cochlear implant or other ear implants
• Implanted drug pumps
• Programmable shunt
• Aneurysm clips and coils
• Stents not located in your heart
• Filters, like blood clot filters
• Metal fragments in your body or eye, like bullets, shrapnel, metal pieces or shavings

Also, you won’t be able to wear certain devices during the MRI. Ask your healthcare provider about how to schedule the MRI if you use:

• A continuous glucose monitor (CGM)
• An insulin pump
• Medication patches

Tell your provider if you:

• Are pregnant or might be pregnant
• Can’t lie on your back for 30 to 60 minutes
• Have claustrophobia

Leave all jewelry and other accessories at home or remove them before the MRI scan. Metal and electronic items aren’t allowed in the exam room because they can interfere with the MRI machine or cause burns. These items include:

• Jewelry, watches, credit cards and hearing aids
• Pins, metal hair accessories, underwire bras and metal zippers
• Removable dental work, like dentures
• Pens, pocketknives and eyeglasses
• Body piercings
• Cell phones, electronic watches and tracking devices

What should I expect during an MRI?

Most MRI exams are painless, but some people find it uncomfortable to remain still for 30 minutes or longer. Others may have anxiety from being in a tight space. The machine can also be noisy.

The general steps of an 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. The MRI scanning bed will slide into the MRI machine.
• As the MRI scan begins, you’ll hear the equipment making loud knocking and clicking sounds while it’s taking the pictures. Each series of sounds may last for several minutes. A provider will give you earplugs or headphones to wear to protect your hearing.
• It’s important to be very still during the exam so the images are clear.
• 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. 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, an MRI may require contrast. If this applies to you, a provider will give you an IV injection of contrast material before the MRI. The IV needle may cause some discomfort, but this won’t last long.

If you have claustrophobia, your provider may recommend giving you medicine that helps you relax during the exam.

How long does an MRI take?

It usually takes 30 to 60 minutes. Your healthcare provider will be able to give you an exact time range based on the specific reason for your scan.

What are the risks and side effects of MRI?

The benefits of getting an MRI outweigh the possible risks. MRI providers take many precautions to keep you safe and comfortable during the test.

Risks of an MRI include:

• Safety concerns related to metal objects or implanted devices
• Claustrophobia or anxiety in the scanner
• Discomfort from noise or lying still during the exam

On very rare occasions, some people who have contrast material for an MRI have mild side effects. These can include nausea, feeling warm or having a metallic taste in your mouth.

What to expect after the test

If you didn’t get medicine to help you relax for the test, there’s no recovery time needed. You can get back to your normal activities right away.

If you did get medicine, you’ll need some time to recover before going home. You’ll also need someone to drive you.

If you had contrast with the MRI, you may have mild side effects. But these effects go away quickly.

When should I know the results of the MRI?

A radiologist will analyze the images and look for growths, inflammation or signs of injury or disease. This can take up to a few days. The radiologist will send a report to your healthcare provider. The report will explain what they saw and whether you need a follow-up appointment.

What type of results do you get and what do the results mean?

MRI results depend on the reason for the scan. It’s usually either normal or abnormal.

Normal results mean nothing concerning was seen. Abnormal results don’t always mean something serious. You may need more testing depending on what is found. Your healthcare provider will go over your results and explain what they mean for you.