What Is Magnetic Resonance Imaging (MRI)?

What to expect when undergoing this test

Woman getting ready for an MRI
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Magnetic resonance imaging (MRI) is a pain-free, noninvasive medical test used to produce two- or three-dimensional images of the structures inside your body using a strong magnetic field and radio waves. MRI gives detailed views of your organs, tissues, and skeleton, which can be used to help diagnose and monitor a wide variety of medical conditions.

Purpose of Test

An MRI scan allows your healthcare team to see the internal structures of your body without making an incision via detailed, high-resolution images. All areas of the body can be scanned from any direction or angle using MRI technology, which means this test can be used for both the diagnosis and monitoring of many health conditions.

MRI can be ordered with or without contrast. Contrast medium is a liquid that's injected into your bloodstream through an IV and can allow more detailed images to be obtained. To provide doctors with a point of comparison, many patients have an MRI scan without contrast immediately followed by another with contrast.

Diagnosis

The detailed images produced by an MRI can be helpful in diagnosing an illness that may be affecting your muscle, organs, or other types of tissues. If your physician suspects that you have an illness or disease process, an MRI may be ordered to help identify the problem. In some cases, a diagnosis can be made with an MRI and may prevent or indicate the need for surgery. It's particularly useful for brain and spinal cord conditions.

Some of the many conditions MRI is used to help diagnose include:

  • Brain and spinal cord conditions such as multiple sclerosis (MS), stroke, brain or spinal cord injuries, brain aneurysms, tumors, and brain injuries
  • Tumors or abnormalities in organs like the liver, spleen, pancreas, reproductive organs, kidneys, bile ducts, bladder, heart, bowel, and adrenal glands
  • Heart and blood vessel structure issues, such as the abnormal size of aortic chambers, damage from a heart attack or heart disease, inflammation, blockages, congenital heart disease, aneurysms, and other heart problems
  • Inflammatory bowel diseases like Crohn's disease or ulcerative colitis
  • Liver diseases like cirrhosis
  • Breast cancer
  • Joint and bone irregularities, tumors, abnormalities, and infections

There's a special type of MRI that's used to evaluate brain activity called functional magnetic resonance imaging (fMRI). It can be used to look at your brain structure, as well as blood flow in your brain, which increases in areas that are active. A fMRI scan can then assess which areas of your brain handle different functions like movement, planning, and language, which can be helpful if you need brain surgery or to check for brain damage from a head injury, brain tumor, stroke, or from the effects of diseases like Alzheimer's.

Monitoring

If you have any of the conditions mentioned above, your doctor may recommend periodic MRI to keep an eye on any changes and to see how well your treatment is working.

Differences and Limitations

An MRI scan is different from a computed tomography (CT) scan, which uses X-rays instead of magnets to produce images. While both tests show images of structures of your body, an MRI is better at showing contrast and details of soft tissue like the brain, muscles, tendons, ligaments, nerves, and spinal cord, while a CT scan is typically better for imaging bones.

For conditions that require frequent imaging, especially brain conditions, MRI is the best choice because it doesn't use X-rays or radiation. For emergency situations, a CT scan is much quicker, so MRI is typically reserved for situations in which there's time to get detailed pictures.

A few other limitations of MRI include:

  • Movement results in blurry, low-quality pictures, so the utility of the images will depend on your ability to lie completely still and hold your breath when asked. If you're in pain or feeling claustrophobic or anxious, this may be difficult to accomplish.
  • If you're having an MRI of your chest, abdomen, or pelvis, breathing and motion in the bowel can cause distortions in the images. However, this isn't as big of a problem with newer machines.
  • MRI can't always show the difference between cancer tissue and fluid buildup (edema), which means additional and/or different testing may be needed.
  • If you're on the large side, you may not fit in the MRI machine, which includes a tube-like enclosure. An open scanner, which doesn't have sides, may be an option instead.
  • In general, MRI scans take longer and cost more than other imaging tests such as a CT scan or X-ray.

Risks and Contraindications

There is no radiation generated by the MRI machine, so the risks of having an MRI are very minimal for the average person.

In the past, people with shellfish allergies could not have contrast as it contained iodine. The most commonly used type of contrast now is a gadolinium-based contrast agent, which can be safely used by people with shellfish or iodine allergies.

That said, there are some things to consider:

  • Infants and young children usually need to be sedated for an MRI, since they may have a hard time holding still during the scan, which is required. This may be necessary for some adults, too. If sedation or anesthesia is used, there's a risk of oversedation.
  • If you have the contrast injection with your MRI, there's a tiny risk of an allergic reaction.
  • If you're claustrophobic or prone to anxiety, you may have a difficult time being in an MRI tube for the time it takes to perform the scan.

Possible Disqualifications

Situations and conditions that may affect your safety should be discussed with your doctor before having an MRI. They include:

  • Metal in your body: If you have a metal device or implant, such as a pacemaker, defibrillator, cochlear implants, or metal clips or coils, you may not be able to have MRI. Since the machine uses very powerful magnets to obtain the images needed, the magnets can potentially attract the metal that's in your body. This restriction applies to other metal objects in your body, such as bullet fragments, metal shards, and similar objects. If you or your doctor are uncertain about the presence of metal in your body (say, she's evaluating you when you are unconscious), she may perform an X-ray to check before proceeding with MRI. Titanium in your body is typically acceptable for an MRI.
  • Implanted medical or electronic devices: These can interfere with imaging results or even create a risky situation for you by causing your device to malfunction. Some implants are safe for MRI once a certain period of time has passed after implantation. Examples of implants you should tell your doctor about are artificial heart valves, metal joint prostheses, nerve stimulators, and metal pins, plates, staples, screws, and stents.
  • Pregnancy: It's unclear what effects strong magnetic fields may have on developing fetuses, especially in the first three to four months, so your doctor may recommend a different imaging test if you are or think you could be pregnant. That said, MRIs have been used since the 1980s on pregnant women and no negative effects for either mother or baby have been reported, so this scan is sometimes used to look at fetuses when necessary. Pregnant women shouldn't have the contrast injection that sometimes accompanies an MRI unless they absolutely need to.
  • Tattoos: Some dark inks have metal in them, so ask your doctor if your body art could impact your test results.
  • Kidney or liver disease: If you have a history of kidney or liver disease, you may not be able to have the contrast injection with your MRI, as this can lead to complications.

Before the Test

If your doctor recommends that you have an MRI scan, she may ask you about some of the above conditions to make sure this is an appropriate test for your situation. This is the time to ask questions about the test and what your doctor is looking for, as well as what the findings might mean for you.

If you have issues with claustrophobia or extreme anxiety, or you're of a larger size, talk to your doctor about the possibility of an open, rather than a traditional, MRI. This type of scanner is open on the sides, allowing for more space and lessening the feeling of being enclosed.

Being able to have an open MRI depends on if your facility has one available and if the open scanner can image the part of your body your doctor wants to learn more about. These scanners are more limited in the types of images they can produce, and older ones don't generate as high-quality imaging as newer versions.

If you are concerned about your reaction while being tested, you may also want to inquire about the possibility of taking a mild sedative like Valium (diazepam), Xanax (alprazolam), or Ativan (lorazepam) before your MRI to help you relax. If one is prescribed, you will need to take it according to your doctor's instructions, usually 30 to 40 minutes before your MRI.

Also ask about the likelihood of sedation/anesthesia and whether or not the test can be done without it. There are some facilities that can perform MRIs while a patient is conscious, so the necessity for this will depend on where the test is being done, what type of MRI is being ordered, and, if a child is being scanned, his or her age and development.

Timing

The whole procedure may take anywhere from 45 minutes to four hours, depending on whether or not you're having anesthesia.

You may spend a few minutes filling out forms before your MRI scan. If you're having an MRI with contrast and/or you're being sedated or having anesthesia, you will have an IV put in before you have the scan as well, so preparation time may take 15 to 20 minutes or so.

The MRI scan itself can take 15 minutes to over an hour, depending on what you're having scanned. For specifics, ask the MRI technologist how long your scan is expected to take.

There is no recovery time unless you've had anesthesia, in which case, it may take another hour or two until you're ready to leave.

You won't need to wait for your test results, which may take a few days to come back.

Location

MRIs are performed at hospitals or imaging centers; your doctor will tell you where to go. The test is performed in one room while the MRI technologist is in another room with the computer equipment. You will be able to communicate with each other while in separate rooms.

What to Wear

Typically, people wear a gown for the MRI scan, but if you have loose fitting clothes that don't have metal fasteners, you may be able to wear that. Be sure to leave any metal jewelry or accessories, as well as electronics, at home or remove them before you enter the MRI room. These objects can interfere with the MRI scans or end up being drawn to the magnetic field and become projectile objects that can be damaged or hurt you or others.

Examples of metal jewelry and accessories you should not have in the MRI room include:

  • Eyeglasses
  • Jewelry and watches
  • Credit cards
  • Hearing aids
  • Pins, hairpins, and zippers
  • Dentures
  • Wigs
  • Body piercings
  • Underwire bras

Food and Drink

For most MRIs, you can eat, drink, and take your medications normally beforehand. Your doctor will let you know if this isn't the case.

If you or your child will be having anesthesia or using a sedative, you will likely need to fast for a specific period of time before the MRI. Be sure to follow your doctor's instructions exactly or the MRI will have to be rescheduled.

Cost and Health Insurance

MRIs are known to be on the expensive side. Hospitals tend to charge more than imaging centers, though many hospitals may have newer equipment, which is a noteworthy positive. Depending on where the test is being done and what part of the body you're having imaged, the cost can be anywhere from $400 to $3,500.

If you have health insurance, your MRI will likely be covered as any diagnostic test would be. You may have to pay a co-pay and/or coinsurance, depending on your plan. For some insurance plans, you may also need to get pre-authorization for an MRI before you have it performed. Contact your insurance agent or the number on your insurance card to be on the safe side.

If you don't have health insurance, you may be eligible for a discount as long as you can pay the total within a certain number of days. Talk to the business or accounting office at the facility at which you'll be getting your test to find out more.

If you have some time before your MRI, it doesn't hurt to get price quotes from different facilities in your area.

What to Bring

If you have a medical device or implant, bring along any information you have about it, such as a pamphlet or card you may have received. This can help the technologist in assessing the safety of the procedure.

Bring your ID and your insurance card, in case the facility where you're having the MRI doesn't have your information.

If you will be sedated or have anesthesia, bring someone along who can drive you home after the MRI.

During the Test

For this test, you will be working with an MRI technologist who will perform the scan and tell you what to do. If you or your child are having anesthesia, you may also be working with a nurse and an anesthesia team.

Pre-Test

You may need to fill out paperwork like a safety screening questionnaire and a consent form before your MRI. The technologist may also review your health and medication history with you, as well as check your heart rate, temperature, and blood pressure.

To prepare for your MRI, you will change into a gown, unless your clothing is deemed safe to wear, and remove all jewelry, glasses, etc. You will then lie down on a table that slides in and out of the MRI scanner. The technologist may use straps to help hold you in the right position and keep you still.

If you're having contrast, an IV sedative, or anesthesia, an IV will be placed in a vein in your hand or arm at this time. The sedative or anesthesia, if ordered, will be administered. This may feel like a sharp pinch or poke, but if it keeps hurting, let the technologist know.

You may have the contrast now or later, after you've had some scans without it. You may experience a cold feeling when the contrast enters your bloodstream. Some people also get a metallic taste in their mouths for a while. If the contrast will be used later, a saline solution is often run through the IV to keep the line open.

Throughout the Test

The actual MRI scan can take anywhere from 15 minutes to over an hour. It's usually completed in 30 to 50 minutes.

When you're in position, the table will be slid into the tube and the technologist will leave the room, but you will be able to talk to him or her at any time, and he or she will be able to see, hear, and speak with you too. The scanner is well-lit and air-conditioned.

To ensure the best quality images, you must hold as still as you can throughout the test. Aside from the discomfort of being in one position until the test is completed, the MRI is not painful. You may feel some warmth in the area of your body that's being scanned, but this is normal. The machine can be rather loud when it's in operation, so earplugs or headphones are usually available or offered; you may also be able to listen to music.

At times, you may be asked to hold your breath for a bit to get good, clear pictures. Let the technologist know if you're experiencing claustrophobia, anxiety, discomfort, or pain from lying still.

After the scans are taken, if you need to have another set done with contrast, you will receive the injection through your IV. Scans may be taken as this is happening or afterward.

Very rarely, people have an allergic reaction to the contrast that causes mild hives and itchy eyes and/or skin. Let the technologist know if you experience any of these symptoms after the contrast is administered. Allergic reactions usually occur within a few minutes after the contrast injection and are easily controlled with medication.

If you're having a functional MRI, you will be asked to perform some tasks like answering easy questions, tapping your fingers together, or listening to sounds.

Post-Test

When your MRI is finished, you may be asked to wait for a few minutes while the technologist or radiologist, a doctor that specializes in reading images like MRI, makes sure they don't need to take any more images.

Once all the imaging is complete, the table will be slid out of the MRI tube, your IV will be taken out (if applicable), and you can get dressed and go home. If you took a sedative, remember that you'll need someone else to drive you.

If you had anesthesia, you will be taken to a recovery room where you will be woken up and allowed to recover before you go home with a family member or friend.

In the extremely rare event that you had an allergic reaction to the contrast injection, you will be allowed to leave as soon as your symptoms are gone.

After the Test

Once you are cleared to leave, you can go home and resume your normal activities and diet.

If you're breastfeeding your baby and you had a contrast injection, the contrast manufacturers recommend that you wait for 24 to 48 hours after your MRI before feeding your baby again to be on the safe side. However, the American College of Radiology says that available evidence points to breastfeeding immediately after receiving contrast being safe.

Managing Side Effects

If you had a contrast injection, you may experience some mild side effects for a few hours that can include a headache, nausea, dizziness, and pain where your IV was, but this is rare.

If you had an IV for any reason, you may have some bruising and/or swelling in the area where your IV was placed. This should go away after a few days, but if it doesn't or it gets worse, call your doctor.

Interpreting Results

MRI results may take a few days to come back, but this varies from facility to facility. Ask your doctor or the MRI technologist about how long you should expect to wait and what you might need to think about in terms of potential results.

A radiologist will look at and interpret your MRI scans. He or she will then write up and send a radiology report detailing the results to your doctor, who will then share the main findings of the MRI with you and talk to you about your next steps.

Unless you're able to access the radiology report in your online medical chart, you probably won't see it. If you do, if may be difficult to make sense of it without some advanced medical knowledge. Your doctor or radiologist can answer any questions you have.

A typical radiology report includes a number of sections (exam type, clinical history, etc.), one of which is the radiologist's findings of each of the areas in your body that were scanned in your MRI. Each area is classified as normal, abnormal, or potentially abnormal.

In the impression section, the most important part of the report, the radiologist combines your medical history with the findings of the MRI and reason for the test and gives a diagnosis based on these factors. If there isn't enough information for a specific diagnosis, the radiologist lists possible diagnoses (differential diagnoses) that may fit your situation.

Follow-Up

You may need to follow-up with your doctor if your MRI results weren't normal. Here are common scenarios:

Abnormal or potentially abnormal: If there is an abnormal or potentially abnormal finding, depending on the circumstances, the radiologist may recommend steps such as:

  • Additional imaging, such as a repeat MRI, a CT scan, ultrasound, X-ray, or nuclear medicine imaging, such as positron-emission tomography (PET)
  • Biopsy
  • Comparing the MRI finding with lab results and/or your symptoms
  • Comparing the MRI to past imaging scans, if possible

Your doctor will discuss a plan regarding how to proceed with you.

Inconclusive: If the MRI didn't find what your doctor was looking for, you will probably have a repeat MRI scan that uses different views or with a special imaging technique, such as a magnetic resonance angiography (MRA) to look at your blood vessels, an fMRI, or MRI with contrast to look more in-depth for whatever your doctor is trying to find. You may also have one of the imaging tests mentioned above instead of or in addition to MRI.

A potentially abnormal finding on your MRI may also warrant a follow-up MRI to see if the area has changed. In either of these situations, your doctor may schedule these as soon as possible.

Diagnosis: In cases where your MRI helped diagnose a specific medical condition, your doctor will talk to you about a treatment plan. You may also have another MRI (or more than one) so that your doctor can monitor the abnormality for changes and see if your treatment is working. This may be scheduled for a later time.

A Word From Verywell

Waiting for test results can be nerve-wracking. Try to find ways to keep your mind off of it, if you can. Go out with a friend, participate in activities you love. Be sure to keep lines of communication open with your doctor and his or her staff so you can ask questions as you go along. Being proactive in your healthcare is important both because it helps you feel less anxious about the process and because you know yourself and what you're going through better than anyone else.

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