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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 produce high-quality, detailed pictures of the inside of the body. 

How Do Doctors Use an MRI?

Doctors use MRI to examine:

  • The brain 
  • The spine
  • Joints (knee, shoulder, hip, wrist, and ankle) 
  • Abdomen
  • Pelvic region 
  • Breast
  • Blood vessels 
  • Heart

It can help your child’s doctor: 

  • Diagnose cancer
  • See if cancer treatment is effective 
  • Monitor remission after cancer treatment

Does an MRI Hurt?

The MRI test is painless. Your child won’t feel the magnetic field or radio waves.

Does an MRI Use Radiation?

MRI does not involve ionizing radiation. MRI scanners use strong magnetic fields and radio waves (radiofrequency energy) to make images. 

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. 

A contrast agent may be used to enhance the quality of the images.

How Long Does an MRI Test Take?

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.

A typical MRI scan will take 60-90 minutes depending on the part of the body being imaged.

How Do You Prepare for an MRI Scan?

Be sure to talk with your child about the upcoming scan. It’s important that your child understands they’ll need to lie still during the test (so it doesn’t have to be repeated). A child life specialist can help.

If you or your child’s care team think staying still may be difficult for your child, a sedative may help. Talk with your child’s care team about it. 

If your child is going to be sedated, they must not eat or drink for several hours before the test. You’ll get more specific instructions from your child’s pediatric center.

The staff will ask you to fill out a screening form that asks about any metal in your child’s body or on their clothing. Let your care team know if your child has any medical implants. 

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 those 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, and retainers
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.

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.

MRI of a femur shows metal artifact that looks like a black shadow over the right femur (arrows). Compare it to the normal left femur (curved arrows) that does not have metal artifact.

MRI of a femur shows metal artifact that looks like a black shadow over the right femur (arrows). Compare it to the normal left femur (curved arrows) that does not have metal artifact.

Because of the MRI’s powerful magnet, you and your child should, if possible, avoid wearing clothing with metal.

It is best to wear clothing without: 

  • Metal snaps
  • Zippers
  • Rivets

At the center

In most pediatric centers, you’ll pass through a metal detector that is more sensitive than the ones in most airports before entering the MRI area. 

Before the test, your child will be asked to change into a hospital gown. You’ll also go through a metal detector to ensure no metal objects are on you or your child.

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.

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

You’ll 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 can’t be removed, then you won’t be allowed to enter the area until a safety specialist says you’re “MRI safe.” 

What Happens During an MRI Test?

Every pediatric center is different, but here’s a look at what you and your child can expect in general:

  • The appointment begins when you and your child check in at the center. If possible, try to arrive a few minutes early.
  • When it’s time for the test, an MRI technologist or nurse will escort you back to the room where the MRI machine is.
  • You’ll 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. 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, sedation to encourage relaxation or sleep may help.
  • The MRI test is painless, but the test is noisy. Your child will get earplugs or noise-reducing headphones to block the noise. They also 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 an adjoining room. They’ll will be able to see, hear, and talk to your child. Your child can communicate with the technologist through a two-way intercom. Each pediatric center has different policies, but usually a parent is allowed to be in the adjoining 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 scan, your child can resume normal activities if they did not have sedation. If your child did receive a sedative, they’ll need to recover first.

Contrast

Your child might receive a contrast agent to help the MRI images appear clearer and brighter. The contrast is given through an IV. If your child doesn’t already have an IV or port, a nurse will start an IV.

A contrast agent called gadolinium is typically used during an MRI. Your child may sense a temporary metallic taste in their mouth after the contrast injection. 

Gadolinium should not be given to anyone who is:

  • Who is pregnant
  • Has had a previous allergic reaction to it 
  • Has severe kidney disease. 

Also, let the care team know if your child has a history of:

  • Heart disease
  • Asthma
  • Diabetes
  • Thyroid problems. 

A few patients experience side effects from the contrast material, including nausea and local pain. Very rarely, patients are allergic to the contrast and experience hives, itchy eyes or other reactions.

 If this happens, a radiologist or other physician will be available to help. 

 

How Do Patients Get Test Results?

A radiologist, a doctor who has special training in reading MRI scans, will look at the images and prepare a report for your child’s doctor. You’ll receive the results during your follow-up appointment.

Childhood cancer patient positioned for full body MRI scan with Dad and two MRI Technologists next to her.

The MRI test is painless, and neither the magnetic field nor the radio waves are felt. 


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does not endorse any branded product mentioned in this article.


Reviewed: October 2021