Cardiac Magnetic Resonance Imaging (cMRI)

Cardiac MRI for children

The Children's Sibley Heart Center is one of the few pediatric healthcare systems in the nation to offer advanced cardiac magnetic resonance imaging (cMRI). This new and exciting cardiology field focuses on improving pediatric cardiac surgery and treatment, and enables doctors to evaluate children with complex heart defects. MRI programs at Children's are accredited by the American College of Radiology (ACR).

What is cMRI?

cMRI is a diagnostic procedure that uses a combination of a large magnet, radiofrequencies and a computer to produce detailed images of organs and structures within the body. MRI of the heart can be used for the following reasons, to:

  • Evaluate the structure/anatomy of the heart and surrounding blood vessels
  • Assess blood flow to the heart muscle
  • Evaluate infections
  • Detect tumors

The MRI machine is a large, tube-shaped machine that creates a strong magnetic field around the patient. This magnetic field, along with a radiofrequency, alters the natural alignment of hydrogen atoms in the body. Computers are then used to form two-dimensional (2-D) images of the heart’s structure based on the activity of the hydrogen atoms. Cross-sectional views can be obtained to reveal further details. MRI does not use radiation, like X-rays or computed tomography (CT) scans.

MRI does not pose any risks unless a child has any kind of implanted metal objects in the body. Parents need to to tell their child’s doctor know if their child has any of the following:

  • Implanted pacemaker
  • Implanted medication device, such as an insulin pump
  • Metal clips or pins, or other metal objects in the body
  • Any bullet wounds, particularly if the bullet remains in the body
  • Any metal joint replacements or heart valve replacements

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What is the preparation for a cMRI?

Parents should make sure their child is not wearing any metal jewelry, hair clips, or barrettes, as these will have to be removed prior to the test.

If the child’s doctor schedules a MRI scan and decides to use contrast dye to enhance the pictures, the child may need to be NPO (fasting, nothing by mouth) for several hours prior to the procedure. Parents will receive instructions about this from the child’s doctor or another healthcare professional.

Parents will need to let their child’s doctor know if their child has ever had a reaction to any contrast dye, or if he is allergic to iodine or seafood. If a teenage daughter is pregnant or could be pregnant, parents should notify the doctor prior to the procedure.

Children may receive a mild sedative before the procedure to make them feel more comfortable, and to help them to remain still and quiet during the procedure, which may last 30 to 60 minutes.

Parents may be able to stay with their child in the MRI room until he becomes sleepy, but are usually asked to wait in another area during the procedure to avoid exposure to unnecessary radiation.

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How is a cMRI performed?

The MRI scanner is located in a large room. The child will lie on a narrow table that slides into the hollow tube-shaped scanner.

The MRI doctor and staff will be in an adjacent room where the equipment controls are located. However, they will be able to see the child through a large window and will be monitoring him constantly during the procedure. If the child is not sedated, he will be given a call bell device to let the staff know if he needs anything during the procedure.

The MRI scanning machine makes loud banging or knocking noises when adjustments are being made. The child will wear a set of headphones to help protect his ears from the noise of the scanner and to hear instructions from the MRI staff. Music may be played in the headphones when instructions are not being given.

Once the procedure begins, the child will need to remain very still at all times so that movement will not adversely affect the quality of the images. At intervals, he will be instructed to hold his breath, if possible, for a few seconds. Then, he will be told when to breathe. The child should not have to hold his breath for longer than a few seconds, so this should not be uncomfortable. Young children who cannot remain still for the procedure will be given medicine to help them relax or sleep during the MRI scan.

If the MRI scan is being done with and without contrast, the child will receive contrast medicine through an I.V. about halfway through the procedure. He may feel a warm or flushed sensation just after the dye goes into the vein—this is a normal sensation and it will go away shortly.

Once the procedure is finished, the table will slide out of the scanner. If the child received medicine for relaxation or sleep, he will be monitored until the medicine wears off and he is awake again. If an I.V. was inserted, it will be taken out after the procedure is done and your child is awake.

The test normally takes approximately 30 to 60 minutes.

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What happens after the procedure?

Without sedation, the child should be able to resume normal activities immediately, unless the child’s doctor instructs him otherwise.

With sedation, the child may feel groggy, tired or sleepy for a period of several hours after the procedure. However, the sedation effects should disappear within a day or so.

Depending on the results of the MRI, additional tests or procedures may be scheduled, to gather further diagnostic information.

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