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Magnetic Resonance Imaging (MRI)

What is an MRI?

An MRI (magnetic resonance imaging) is a type of imaging test. It uses a large magnet, radio waves, and computers to make high-quality, detailed pictures of the inside of the body. 

Doctors may use an MRI to look at your child’s:

  • Brain 
  • Spine
  • Face and neck
  • Bone and Joints (knee, shoulder, hip, wrist, and ankle) 
  • Chest 
  • Abdomen and pelvic region 
  • Breast
  • Blood vessels 
  • Heart

Watch this video to learn about MRIs for childhood cancer.

The MRI scan is painless. Your child will not feel the magnetic field or radio waves.

Your health care provider may order an MRI scan with contrast. Contrast agents are clear liquids that are swallowed or injected into a vein by IV. The contrast material can highlight certain areas of the body on the scan. Sometimes a contrast agent is needed to make the images even more clear and detailed.

How MRI works 

MRI does not involve radiation. During an MRI exam, your child will be inside a strong magnetic field. Then radio waves are sent from and received by the machine. These signals make digital images of the scanned body part.  

How to prepare for an MRI scan

Patient positioned for MRI of her leg with Child Life specialist and two MRI technologists.

A typical MRI scan will take 20-90 minutes depending on the part of the body being imaged.

Each center has its own process. Talk to your care team about what to expect and how to prepare for your appointment.

Talk to your child about staying still: It is important that your child knows what to expect and understands they will need to lie still during the test. A child life specialist or other care team member might help your child with relaxation techniques. Some centers even have a mock MRI scanner where your child can practice getting an MRI before getting the scan. 

Comfort items: Some centers will allow your child to bring a comfort item, like a stuffed animal or a blanket, while others will not. Ask your care team if your child can bring a comfort item to the appointment.

Eating and drinking before the scan: Follow your care team’s instructions for what your child can eat or drink before the scan. If your child is going to have general anesthesia, they must not eat or drink for several hours before the test. You will get more specific instructions from your child’s care team.

Checking-in for your appointment: Be sure to arrive a few minutes early. Check in at the registration desk with your child. Then wait until your child’s name is called.

Be sure to let the care team know if your child:

  • Is uncomfortable in small spaces
  • Has trouble staying still or has certain behavior needs 
  • Might be pregnant
  • Is allergic to contrast agents or iodine
  • Has diabetes or kidney problems

What to wear: Be sure your child dresses in loose, comfortable clothing. Some care centers will require your child to change into an MRI-safe gown, pants, and socks. Both you and your child should avoid clothing and accessories that contain metal. That includes:

  • Belts
  • Zippers
  • Snaps
  • Rivets
  • Buttons
  • Hair accessories
  • Glitter
  • Watch
  • Jewelry
  • A non-permanent retainer 
  • Glasses 
MRI with metal artifact from braces cause bright and dark lines across the image (arrows) and a black shadow (curved arrows) that covers up the area of interest.

In this MRI, the patient’s metal braces cause bright and dark lines across the image. This makes it difficult to see the area being scanned.

Metal and the MRI

The staff will ask you to fill out a form that asks about any metal in your child’s body or on their clothing. Since the MRI uses a strong magnet to take pictures, your child will need to remove any metal before the scan. Let your care team know if your child has any medical implants. Your care team will let you know if your child is eligible for the MRI scan.

Objects that may interfere with image quality if close to the area being scanned include:

  • Metallic spinal rod
  • Plates, pins, screws, or metal mesh used to repair a bone or joint 
  • Joint replacement or prosthesis
  • Metallic jewelry, including that used for body piercing 
  • Some tattoos or tattooed eyeliner (there is also a chance of skin irritation or swelling)
  • Makeup, nail polish, or other cosmetics that contain metal 
  • Dental fillings, orthodontic braces (the center may require arch wires to be removed before the scan), and retainers

Metal detector at the treatment center

Pediatric cancer patient's father hands cell phone to MRI technologist after metal detector scan.

Anyone entering the MRI area must pass through a metal detector that is more sensitive than the ones in most airports.

Before the test, your child will be asked to change into a hospital gown. Then you and your child will go through a metal detector to make sure no metal objects are on you.

You will need to remove these items:

  • Purse, wallet, money clip, credit cards, cards with magnetic strips
  • Electronic devices such as cell phones
  • Hearing aids
  • Metal jewelry, watches
  • Pens, paper clips, keys, coins
  • Hair barrettes, hairpins
  • Any article of clothing that has a metal zipper, buttons, snaps, hooks, underwire, or metal threads
  • Shoes, belt buckles, safety pins
  • Medication patches

If the detector shows you have metal on your body, you will likely have to remove the metal and be screened again. If it cannot be removed, then you cannot enter the area until a safety specialist says you are “MRI safe.” 

MRI Scans with Anesthesia

Your child must stay still during the MRI scan so that images do not blur. In some cases, your child may get sedation medicines or general anesthesia for an MRI scan. 

  • Sedation uses medicines that cause relaxation or sleepiness
  • General anesthesia causes a complete loss of consciousness, like a very deep sleep

Anesthesia is safe for most patients. But health care providers try to limit the use of general anesthesia in children. Talk to your care team about options for your child. There might be other ways to help your child stay still during imaging tests.


What to expect during an MRI scan

Every center is different. But in general, your child’s MRI appointment will likely include the following:

  • The appointment begins when you and your child check in at the center. Most centers will ask that you arrive early.
  • When it is time for the test, an MRI technologist or nurse will take you back to the room where the MRI machine is.
  • You will see that the MRI machine looks like a large donut with a tunnel in the middle. It contains a padded table (sometimes called a bed) that slides in and out of the tunnel. 
  • Your child will lie on the table for the test and must stay still while the MRI is underway. The care team may use safety belts to place over your child. Moving during the test will blur the image. That means the test will have to be repeated. 
  • A child life specialist can work with your child on relaxation techniques. Your child may also listen to music or watch a movie using special goggles. 
  • If your child has issues staying still, the care team may suggest sedation medicines to help your child relax.
  • The MRI test is painless, but the test is noisy. There will be loud noise during the entire time that images are being taken. Your child will get earplugs or noise-reducing headphones to block the noise and protect hearing. Your child will also be given a squeeze-ball to use in case they need anything during the scan.
  • During the test, the technologist will move to another room. They will be able to see, hear, and talk to your child. Your child can talk with the technologist through a 2-way intercom. Each treatment center has different policies, but usually a parent is allowed to be in the next room with the technologist.
  • A typical MRI scan will take 60–90 minutes, depending on the part of the body that is scanned.

After the MRI scan

When the scan is complete, the technologist will unfasten safety belts and disconnect the IV, if one was used. Then your child may get off the table and leave the area. 

Your child can resume normal activities if they did not have sedation or general anesthesia. If your child did get these medicines, they will need to recover first. 

A doctor called a radiologist will prepare a report of the results for your child’s care team. The report may take a few days.

Your health care provider will discuss the results of the MRI scan with you. 

Possible risks of MRI scans

MRIs usually have no side effects. Minimal side effects may include: 

  • Hearing problems if ear protection is not used
  • Discomfort of being in tight enclosed spaces
  • Increased body temperature due to radio waves

Side effects of contrast

If a contrast agent is used for the MRI scan, your child might have minor side effects. These include:

  • Local pain where IV is inserted
  • Headache
  • Feeling dizzy
  • Feeling warm or flushed
  • Strange taste in the mouth
  • Nausea or vomiting
  • Allergic reaction (hives, itchy eyes)

If you have any questions about MRI side effects or safety, talk with your child’s care team. Learn more about types of imaging tests.

Questions to ask your care team

  • Why is the MRI scan needed?
  • How will the results be used?
  • How long will the scan take?
  • Does my child need to stop eating or drinking before the test?
  • Can my child listen to music or watch movies during the scan?
  • Can a caregiver be in the room during the scan?
  • Will my child get sedation medicines or general anesthesia?
  • What are the risks or side effects of the MRI?
  • When and how will we get the MRI results?

Key points about MRI scans

  • An MRI scan uses a large magnet, radio waves, and computers to make detailed pictures of the inside of the body. 
  • MRI tests are safe and painless. They can take 60–90 minutes.
  • MRI tests do not involve radiation.
  • Your child will have to stay still for the scan so that the images will be clear.
  • Follow any instructions from your child’s care team exactly.
  • Ask your child’s care team if you have questions about MRI tests.

The Together by St. Jude online resource does not endorse any branded product mentioned in this article.

Reviewed: January 2024