MRI (Magnetic Resonance Imaging)
What is an MRI?
An MRI (magnetic resonance imaging) scan is a painless test that produces very clear images of the organs and structures inside your body. MRI uses a large magnet, radio waves and a computer to produce these detailed images. It doesn’t use X-rays (radiation).
Because MRI doesn’t use X-rays or other radiation, it’s the imaging test of choice when people will need frequent imaging for diagnosis or treatment monitoring, especially of their brain.
What is an open MRI?
An open (or “open bore”) MRI refers to the type of machine that takes the images. Typically, an open MRI machine has two flat magnets positioned over and under you with a large space between them for you to lie. This allows for open space on two sides and alleviates much of the claustrophobia many people experience with closed-bore MRI machines.
However, open MRIs don’t take as clear images as closed-bore MRI machines. Closed-bore MRI machines have a ring of magnets that forms an open hole or tube in the middle where you’d lie to get the images. Closed-bore MRIs are narrow with tight head-to-ceiling space. This can cause anxiety and discomfort for some people, but these MRI machines take the best quality images.
If you’re nervous about your MRI scan or have a fear of closed spaces, talk to your healthcare provider. If needed, your provider will discuss options for sedatives (medicines to make you feel relaxed) or even anesthesia if necessary.
What is an MRI with contrast?
Some MRI exams use an injection of contrast material. The contrast agent contains 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:
If your MRI requires a contrast material, a 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 drugs. Side effects ranging from mild to severe do occur, but severe reactions are very rare.
What’s the difference between an MRI scan and a CT scan?
Magnetic resonance imaging (MRI) uses magnets, radio waves and a computer to create images of the inside of your body, whereas computed tomography (CT) uses X-rays and computers.
Healthcare providers often prefer to use MRI scans instead of CT scans to look at the non-bony parts or soft tissues inside your body. MRI scans are also safer since they don’t use the damaging ionizing radiation of X-rays.
MRI scans also take much clearer pictures of your brain, spinal cord, nerves, muscles, ligaments and tendons than regular X-rays and CT scans.
However, not everyone can undergo an MRI. The magnetic field of MRI can displace metal implants or affect the function of devices such as pacemakers and insulin pumps. If this is the case, a CT scan is the next best option.
MRI scanning is usually more expensive than X-ray imaging or CT scanning.
What does an MRI show?
Magnetic resonance imaging (MRI) produces detailed images of the inside of your body. Healthcare providers can “look at” and evaluate several different structures inside your body using MRI, including:
- Your brain and surrounding nerve tissue.
- Organs in your chest and abdomen, including your heart, liver, biliary tract, kidneys, spleen, bowel, pancreas and adrenal glands.
- Breast tissue.
- Your spine and spinal cord.
- Pelvic organs, including your bladder and reproductive organs (uterus and ovaries in people assigned female at birth and the prostate gland in people assigned male at birth)
- Blood vessels.
- Lymph nodes.
When would I need an MRI?
Healthcare providers use magnetic resonance imaging (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 spinal cord MRIs can help evaluate and diagnose the following conditions:
- Brain aneurysms.
- Brain tumors and spinal tumors.
- Brain and spine injuries from trauma.
- Compression or inflammation of spinal cord and nerves (pinched nerve).
- Multiple sclerosis (MS).
- Spinal cord conditions.
- Spine anatomy and alignment.
Providers use cardiac (heart) MRIs for several reasons, including:
- To evaluate the anatomy and function of your heart chambers, heart valves, size of and blood flow through major vessels and the surrounding structures.
- To diagnose cardiovascular conditions, such as tumors, infections and inflammatory conditions.
- To evaluate the effects of coronary artery disease, such as limited blood flow to your heart muscle and scarring within your heart muscle after a heart attack.
- To evaluate the anatomy and function of the heart and blood vessels in children and adults with congenital heart disease.
Body MRIs can evaluate structures and diagnose several conditions, including:
- Tumors in your chest, abdomen or pelvis.
- Liver diseases, such as cirrhosis, and issues with your bile ducts and pancreas.
- Inflammatory bowel disease, such as Crohn's disease and ulcerative colitis.
- Malformations of blood vessels and inflammation of the vessels (vasculitis).
- A growing baby in the womb.
MRIs of bones and joints can help evaluate:
- Bone infections (osteomyelitis).
- Bone tumors.
- Disk abnormalities in your spine.
- Joint issues caused by injuries.
Is an MRI safe?
An MRI scan is generally safe and poses almost no risk to the average person when appropriate safety guidelines are followed.
The strong magnetic field the MRI machines emit is not harmful to you, but it may cause implanted medical devices to malfunction or distort the images.
There’s a very slight risk of an allergic reaction if your MRI requires the use of contrast material. These reactions are usually mild and controllable by medication. If you have an allergic reaction, a healthcare provider will be available for immediate assistance.
Healthcare providers generally don’t perform gadolinium contrast-enhanced MRIs on pregnant people due to unknown risks to the developing baby unless it’s absolutely necessary.
Who shouldn’t get an MRI?
In most cases, an MRI exam is safe for people with metal implants, except for a few types. Unless the device you have is certified as MRI safe, you might not be able to have an MRI. These devices may include:
- Metallic joint prostheses.
- Some cochlear implants.
- Some types of clips used for brain aneurysms.
- Some types of metal coils placed within blood vessels.
- Some older cardiac defibrillators and pacemakers.
- Vagal nerve stimulators.
If your healthcare provider recommends an MRI scan, they’ll ask detailed questions about your medical history and any medical devices or implants you may have in or on your body.
Who performs an MRI?
A radiologist or a radiology technologist will perform your 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 an MRI work?
Magnetic resonance imaging (MRI) works by passing an electric current through coiled wires to create a temporary magnetic field in your body. A transmitter/receiver in the machine then sends and receives radio waves. The computer then uses these signals to make digital images of the scanned area of your body.
What do I need to do to prepare for an MRI?
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 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 MRI scan. 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.
Please tell your provider and MRI technologist if you have any of the following:
- Heart pacemaker or defibrillator.
- Electronic or implanted stimulators or devices, including deep brain stimulators, vagus nerve stimulators, bladder stimulators, spine stimulators, neurostimulators and implanted electrodes or wires.
- Metallic joint prostheses.
- Cochlear implant or other ear implants.
- Implanted drug pumps, such as those that pump narcotic/pain medications or drugs to treat spasticity.
- Programmable shunt.
- Aneurysm clips and coils.
- Stents not located in your heart.
- Filters, such as blood clot filters.
- Metal fragments in your body or eye, such as bullets, shrapnel, metal pieces or shavings.
You won’t be able to wear the following devices during your MRI. Please coordinate your MRI appointment with the day you need to change your patch or device.
In addition, tell your provider if you:
- Are pregnant.
- Are not 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 MRI scan. 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.
How long does an MRI scan take?
Depending on the type of exam and the equipment used, the entire exam usually takes 30 to 50 minutes to complete. Your healthcare provider will be able to give you a more exact time range based on the specific reason for your scan.
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 experience anxiety from the closed-in space while in the MRI machine. 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 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.
- 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, a 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 provider may recommend a sedative drug so you feel more relaxed during the exam or even anesthesia.
What are the side effects of MRI contrast?
On very rare occasions, some people who have contrast material for their MRI experience side effects, including:
- Pain at the site of the injection.
It’s very rare to experience hives, itchy eyes or other signs of an allergic reaction to the contrast material. If you have allergic symptoms, tell the technologist. A healthcare provider will be available to provide immediate medical care.
Nephrogenic systemic fibrosis (NSF), which causes thickening of your skin, organs and other tissues, is a rare complication in people with kidney disease that undergo an MRI with contrast material. Because of this, people with severe kidney disease may not be able to have gadolinium-based contrast material for their MRI.
There’s evidence that tiny traces of gadolinium may stay in different organs of your body after contrast-enhanced MRI. While there are no known negative effects from this, your provider may take gadolinium retention into account when selecting a contrast agent.
What should I expect after an MRI?
If you didn’t have a sedative drug for the MRI scan, no recovery period is necessary. You can go home and resume your normal activities. If you had sedative drugs for the exam, you’ll need to recover from the effects of them before you can go home. You may need to have someone else drive you home.
Results and Follow-Up
When should I know the results of my MRI?
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. You may need a follow-up exam. If so, your provider will explain why.
A note from Cleveland Clinic
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 an MRI scan and are worried about the exam or have questions about it, don’t be afraid to ask your healthcare provider. They’re available to help and support you.
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