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Magnetic Resonance Imaging (MRI)

What is an MRI?

MRI (magnetic resonance imaging) uses a large magnet, radio waves, and computers to produce high-quality, detailed pictures of the inside of the body. The MRI test is painless. Patients do not feel the magnetic field or radio waves.

Physicians use MRI to examine the brain, spine, joints (knee, shoulder, hip, wrist, and ankle), abdomen, pelvic region, breast, blood vessels, heart, and other body parts. MRIs can be used to help diagnose disease, including cancer; observe the progress of treatment; and to monitor remission in patients who have completed treatment.

MRI does not involve ionizing radiation. A contrast material may be used to enhance the quality of the images.

MRI scanners use strong magnetic fields and radio waves (radiofrequency energy) to make images. During an MRI exam, the patient is placed inside a strong magnetic field. Then radio waves are sent from and received by a transmitter/receiver in the machine to examine the part of the body under study, and these signals are used to make digital images of the scanned area of the body.

What Happens During an MRI?

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.

  • An MRI appointment begins with the patient and parent checking in at the registration desk and waiting to be called back for the test. It is important to arrive a few minutes before the appointment to allow for check-in.
  • When it’s time for the test, a MRI technologist or nurse will escort the patient and parent back to the room that houses the MR system or “scanner.”
  • An 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. The patient lies on the table for the test and must stay still while the MRI is underway. Moving during the test will blur the acquired image, and the test will have to be repeated. A child life specialist can work with patients on relaxation techniques. Patients may also listen to music or watch a movie using special goggles. Patients who have problems with remaining still may receive sedation so they can relax or sleep during the process.
  • The MRI test is painless, and neither the magnetic field nor the radio waves are felt. But the test is very noisy. Patients will be given earplugs or noise-reducing headphones to block noise and protect hearing.
  • During the test, the technologist will move to an adjoining room and will be able to see, hear, and talk to the patient. The patient 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 20-90 minutes, depending on the part of the body being imaged.
  • After the scan, patients can resume normal activities if they did not have sedation. Patients who did receive a sedative will need to recover first.

MRI with Contrast

In some cases, patients will receive a contrast agent to help the MRI images appear even clearer and brighter. The contrast is given through an IV. If the patient does not already have an IV or port, a nurse will start an IV.

A contrast agent called gadolinium is typically used during an MRI. Gadolinium should not be given to patients who are pregnant, have had a previous allergic reaction to this substance, or who have severe kidney disease. Also, parents should let the medical team know if the patient has a history of heart disease, asthma, diabetes, or thyroid problems. Some patients may sense a temporary metallic taste in their mouth after the contrast injection. 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 for immediate assistance.

MRI of the abdomen or abdomen and pelvis combined

If the doctor schedules a MRI scan of the abdomen or abdomen and pelvis, the patient may be given a drug called hyoscyamine (Levsin®) intravenously (by vein). This medicine will decrease the motion of the bowel during the MRI scan and make the MRI picture clearer.

Possible side effects of hyoscyamine (Levsin®) include flushing of the skin, increased heart rate, mild stomach pain, and constipation. These side effects are usually mild. Patients will not be given hyoscyamine (Levsin®) if they have certain known medical conditions, or are taking a medicine that might increase the chance of a bad reaction.

How to Prepare for an MRI

If patients will be sedated, they must not eat or drink for several hours before the test. Patients and families will be given specific instructions at their pediatric center.

Because of the MRI’s powerful magnet, patients and parents (if accompanying) must remove any metallic items before entering the area with the MRI.

Before the patient or parent enters the MRI area, the staff will ask the parent to fill out a screening form that asks about any metal in the patient’s body or clothing. It is best to wear clothing without metal snaps, zippers, or rivets. Parents should inform the medical team about any medical implants used in the patient. Patients may be given a hospital gown to wear.

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.

Items that must be removed include:

  • 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

In most pediatric centers, anyone entering the MRI area must pass through a metal detector that is more sensitive than the ones in most airports. If the detector shows that the person has metal on or in the body, this person will have to remove the metal and be screened again. If the metal cannot be removed, the person must not enter the area, until a qualified MR safety specialist determines that it is “MRI safe.”

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

MRI with metal artifact from braces

MRI of a femur that shows metal artifact

MRI of a femur that shows metal artifact

MRI Results

A radiologist, a doctor who has special training in reading MRI scans, will analyze the images and prepare a report for the referring physician. The referring physician will go over the results of the test during the patient’s next 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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Reviewed: June 2018