MRI (magnetic resonance imaging) is a diagnostic procedure that uses a combination of a large magnet, radio waves, 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 heart's structure
To assess blood flow to the heart muscle
To evaluate infections
To find tumors
To assess blood flow to and from the lungs and the body
To measure the size of the heart's chambers
To measure the size of the heart's major blood vessels
The MRI machine is a large, cylindrical (tube-shaped) machine that creates a strong magnetic field around the patient. This magnetic field, along with radio waves, alters the natural alignment of hydrogen atoms in the body. Computers are then used to form 2-dimensional images of the heart's structure based on the activity of the hydrogen atoms. Cross-sectional views can be taken to reveal more details. MRI does not use ionizing radiation, like X-rays or computed tomography (CT scans).
MRI does not pose any risks unless your child has any kind of implanted metal objects in the body. Be sure to let your child's health care provider know if your child has any of the following:
Implanted medicine device, like 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
Risks and possible complications include:
Problems with undetected metal implants or foreign bodies
Reaction, like headaches, shivering, and vomiting, to sedative or anesthesia
Allergic reaction, like hives, itching, or wheezing, to contrast dye
Rarely, kidney damage from IV contrast dye
Extremely rarely, an illness called nephrogenic systemic fibrosis that has been linked to MRI IV contrast material
Make sure your child is not wearing any metal jewelry, hair clips, or barrettes. These will have to be removed before the test.
If your child's health care provider schedules a MRI scan and decides to use contrast dye to enhance the pictures, your child may need to be NPO (fasting, nothing by mouth) for several hours prior to the procedure. You will receive instructions about this from your child's health care provider or another health care professional.
You will need to let your child's health care provider know if your child has ever had a reaction to any MRI contrast dye, or if he she is allergic to iodine. The risk of a serious allergic reaction to MRI contrast materials is rare, and radiology departments are equipped to handle them. A reported seafood allergy is not considered to be a reason not to use contrast. If your teenage daughter is pregnant or could be pregnant, you should notify the health care provider before 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. The procedure may last 30 to 60 minutes.
Parents may be able to stay with their child in the MRI room until he or she becomes sleepy. They are usually asked to wait in another area during the procedure. One or both parents may be allowed to stay with their child during the procedure under certain conditions.
You can help your child by preparing him or her in advance. How you do this depends on your child’s needs.
Explain the test to your child in brief and simple terms. Younger children have shorter attention spans, so do this shortly before the test. Older children can be given more time to understand the test in advance.
Make sure your child understands which body part(s) will be involved in the test.
As best you can, describe how the test will feel. An IV may be inserted into the arm or hand to give medicines or contrast dye. This may cause a brief sting. Your child won’t feel any discomfort once the medicines take effect. If awake, your child may become uncomfortable from lying still.
Allow your child to ask questions and answer these questions truthfully. Your child may feel nervous or afraid. He or she may even cry. Let your child know that you’ll be nearby during the test.
Many hospitals have a child life specialist. This person is specially trained to help children understand what to expect during their time in the hospital. Books, videos, dolls, and toys may be used to help explain the procedure to your child. Be sure to ask your child’s health care provider about the resources available at your hospital.
The MRI scanner is located in a large room. Your child will lie on a narrow table that slides into the hollow tube-shaped scanner.
The MRI technologist will be in a nearby room where the equipment controls are located. However, they will be able to see your child through a large window. They will be monitoring him or her constantly during the procedure. If your child is not sedated, he or she will be given a call bell device to let the staff know if he or she needs anything during the procedure.
The MRI scanning machine makes loud banging or knocking noises when adjustments are being made. Your child will wear a set of headphones to help protect his or her 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, your child will need to remain very still at all times. Movement will adversely affect the quality of the images. At certain times, he or she will be instructed to hold his or her breath, if possible, for a few seconds. He or she will then be told when to breathe. Your child should not have to hold his or her 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," your child will receive contrast medicine through an IV about halfway through the procedure. He or she 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 your child received medicine for relaxation or sleep, he or she will be monitored until the medicine wears off and he or she is awake again. If an IV was inserted, it will be taken out after the procedure is over and your child is awake.
The test normally takes approximately 30 to 60 minutes. Some may take a couple of hours.
Without sedation, your child should be able to resume normal activities right away, unless your child's health care provider instructs you otherwise.
With sedation, your 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 more diagnostic information.