Conditions + Treatments

Cardiovascular MRI In-Depth

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What is Magnetic Resonance Imaging (MRI)?

An MRI is a way to take pictures of the body using a large magnet, radio waves and a computer. It’s considered a "non-invasive" test because the machine takes pictures without touching the body. MRI doesn’t use x-rays or any radioactive radiation.

When is an MRI necessary?

MRI is done to evaluate the structure and function of the heart and blood vessels. Your child’s cardiologist (heart doctor) requests this test to find out more about the structure and function of the heart and blood vessels. An MRI may provide your child’s cardiologist with information that can’t be obtained by other tests.

How does an MRI work?

An MRI examination of the heart usually lasts 45 to 90 minutes. Here’s what you can expect:

  • The MRI machine sits in a large room and looks like a tunnel. Your child will lie down on a table that slides into the tunnel.
  • One parent can remain in the MRI room during the exam. No one who is pregnant can get an MRI or stay in the room for safety reasons.
  • A technologist operates the MRI machine from outside the room behind a glass window. He’ll talk and listen to your child through an intercom.
  • The MRI machine makes loud banging and clicking noises during most of the exam. We’ll give your child earplugs to soften the noise.
  • Your child can watch a movie or listen to music during the cardiovascular MRI.
  • During the exam your child may be asked to hold her breath for brief periods (10 to 20 seconds). This helps create clearer pictures.
  • Most patients receive a contrast dye, called gadolinium, during the exam to help obtain a better picture of blood vessels. The medicine is given through an intravenous line (IV) placed before the exam. A cream that numbs the skin may be applied before the IV is placed. Patients need to arrive an hour before the exam time to allow time for the cream to numb the skin.

Will my child need sedation or anesthesia?

To obtain clear pictures, your child needs to remain still in the MRI scanner during the test. Young children and some older patients who are unable to lie still or are too afraid of the machine need to have general anesthesia during the examination.

Patients who are scheduled for general anesthesia have an appointment at the Cardiology Pre-Op Clinic a few days before the MRI. During the visit, your child will have a physical check-up, and you will have a chance to meet the anesthesiologist and ask questions.

Some children may experience anxiety inside the tunnel (claustrophobia). Most of the time, this feeling disappears after they get used to the tunnel. If you feel your child might have claustrophobia, please let your doctor know well in advance.

Eating and drinking instructions if your child is receiving anesthesia

In the six hours before the scan, don’t give your child any solid foods or full liquids. For example, if the MRI is scheduled for 10 a.m., stop giving her solid foods and full liquids at 4 a.m.

Examples of solid foods are:

  • cereals
  • bread
  • candy

Examples of full liquids are:

  • milk
  • formula
  • orange juice

You may give your child clear liquids up to three hours before the time of the MRI. For example, if the MRI is scheduled for 10 a.m., stop giving clear liquids at 7 a.m.

Examples of clear liquids are:

  • water
  • ginger ale
  • tea without milk
  • broth

If you are nursing and your child is six months old or younger, you may give your child breast milk up to three hours before the MRI is scheduled.

Eating and drinking instructions if your child is not receiving anesthesia

Your child should not eat or drink one hour before the scheduled exam.

Do not wear

The following items can affect the way the magnet works, so please do not wear them:

  • metal zippers, buttons or snaps
  • Hanes' brand underwear
  • barrettes
  • hairpins
  • jewelry, other than 14k gold
  • watch


For children, it is helpful to explain in an age-appropriate way why the MRI is needed and what to expect. Let your child know that you will be nearby during the scan. Bring a favorite storybook or toy for the waiting time. Bring a special blanket or small stuffed animal for your child to hold during the MRI.

Kids can watch a movie or listen to music during the MRI, so feel free to bring along a favorite selection.


Please make your travel plans carefully to ensure that you arrive on time. Keep in mind that traffic around the medical area is very congested. If you are late, the MRI may have to be rescheduled or delayed. Every effort will be made to keep MRI exams on time, but sometimes an emergency may delay the schedule.

If you have to reschedule, please contact our scheduling office 617-355-2797 as soon as possible. Please keep in mind that many patients like you are waiting to get their MRI test, and if you miss the appointment or don’t let us know at least several days in advance, we can’t use the machine for another patient.

If your child is scheduled for anesthesia, please arrive no later than one hour before the exam time.

If your child is not scheduled for sedation or anesthesia, please arrive no later than 30 minutes before the exam time.

After arriving at the hospital, proceed to the 6th floor of the Main South building. Once you enter the hospital, take the Main elevators up to the sixth floor and look for the signs for 6 South.

Before the exam begins

After you fill out a screening form, a nurse will explain the exam, answer your questions and let you or your child know if you need to change into a hospital gown.

A nurse or technologist will then put ECG leads (stickers) on your child's chest or back.

All patients who need gadolinium (contrast dye), anesthesia or a drug test require an intravenous line (IV). A cream that numbs the skin may be applied before the IV is placed (patients need to arrive one hour prior to the exam time to allow time for the cream to take effect).

During the scan

You may stay with your child during the MRI. If you are pregnant, you may bring someone to stay with your child (only one person may stay). You will be asked to remove watches, credit cards and all jewelry, except 14k gold. These items will be kept in a locker.

Your child may watch a movie or listen to music or a radio program during the test. You can bring your child’s favorite film or music with you.

The technologist who operates the MRI machine will talk and listen to your child through a two-way speaker.

After the exam

If your child received anesthesia, she will go to the catheterization lab recovery room. When your child is fully awake and can drink, she’ll be ready to go home. This takes about one to two hours.

Older patients who receive anesthesia, sedation or Valium (or a similar medication) must have a responsible adult with them when they leave the hospital. Any patient who receives sedation isn’t allowed to drive home. If a ride has not been arranged, the procedure will be rescheduled.

How will we be informed of the results?

When the MRI scan is finished, the cardiac MRI specialist will review the images. We’ll report the results to your child's cardiologist, who will call you with the results, usually within several days.

Other information

If you must cancel the MRI appointment, please call 617-355-2797 at least three days before the scan. For cancellation the night before the scheduled test, please leave a message at 617-355-6300. This phone is answered throughout the night.

Patients with pacemakers, defibrillators and certain implants may not be able to have an MRI. If you have any questions, please discuss with your cardiologist or call us at 617-355-2797.

Boston Children’s is so much more than a hospital—it’s a community of researchers, clinicians, administrators, support staff, innovators, teachers, patients and families, all working together to make the impossible possible. ”
- Sandra L. Fenwick, President and CEO

Boston Children's Hospital
300 Longwood Avenue, Boston, MA 02115
For Patients: 617-355-6000
For Referring Providers: 844-BCH-PEDS | 844-224-7337