Magnetic Resonance Imaging (MRI)

What is an MRI?

Magnetic resonance imaging (MRI) uses a large magnet, radio signals and a computer to produce detailed images of organs and structures within the body. MRI is used to help diagnose various health problems. Unlike X-rays or computed tomography (CT) scans, there is no radiation exposure during an MRI.

The MRI machine is a large, tube-shaped machine that creates a strong magnetic field around your body. Some look like narrow tunnels. Other machines are more open.

MRI uses strong magnets. Metal is affected by magnets and can distort the image. The magnet used in MRI can cause metal objects in your body to move. If you have a metal implant, you may not be able to have an MRI unless the implant is certified as MRI safe. People with these implants should not have an MRI:

  • Ear (cochlear) implants
  • Certain clips used for brain aneurysms
  • Certain metal coils put in blood vessels
  • Most defibrillators
  • Most pacemakers
Getting ready for an MRI

Your doctor will explain the procedure to you and give you a chance to ask questions.

Generally, there is no special restriction on diet or activity prior to an MRI procedure.

If your procedure involves the use of contrast dye, you will be asked to sign a consent form that gives permission to do the procedure. Read the form carefully and ask questions if anything is not clear.

Before the MRI, be sure to tell the technologist if any of the following apply to you:

  • You are claustrophobic and think that you will be unable to lie still inside the scanning machine
  • You have a pacemaker or have had heart valves replaced
  • You have any type of implanted pump, such as an insulin pump
  • You have metal plates, pins, metal implants, surgical staples, or aneurysm clips
  • You have any metallic fragments anywhere in the body
  • You have permanent eyeliner or tattoos
  • You are pregnant or think you may be pregnant
  • You have ever had a bullet wound
  • You have ever worked with metal (for example, a metal grinder or welder)
  • You have any body piercings
  • You have an intrauterine device (IUD)
  • You are wearing a medicine patch
  • You are allergic to X-ray dye (contrast medium), iodine, shellfish, or any medicines
  • Have any serious health problems. This includes kidney disease or a liver transplant. You may not be able to have the contrast material used for MRI.

There is a possibility that you may get a sedative before the procedure, so you should plan to have someone drive you home afterward.

Based on your medical condition, your doctor may request other specific preparation.

What happens during an MRI?
  • You'll be asked to remove your watch, jewelry, hearing aids, credit cards, pens, pocket knives, eyeglasses, and other metal objects. You may be asked to remove your makeup. Makeup may contain some metal.
  • You may be asked to wear a hospital gown.
  • You may be given earplugs or a headset with music to help block out the noise from the scanner. During the test, you will hear clicking and thumping noises.
  • You may be injected with a special dye (contrast) that improves the MRI image. 
  • You’ll lie down on a table that slides into the large circular opening of the MRI machine.
  • The technologist will be in another room where the scanner controls are located. However, you will be in constant sight of the technologist through a window. Speakers inside the scanner allow the technologist to talk to you and hear you. You will have a call button so that you can let the technologist know if you have any problems during the procedure. The technologist will be watching you at all times and will be in constant communication.
  • It will be important for you to stay very still during the exam. Any movement could cause distortion and affect the quality of the scan.
  • At intervals, you may be told to hold your breath, or not to breathe for a few seconds. You will then be told when you can breathe. You should not have to hold your breath for longer than a few seconds.
  • If contrast dye is used, you may feel some effects when the dye is injected into the IV line. These effects include a warm flushing sensation or a feeling of coldness, a salty or metallic taste in the mouth, a brief headache, itching, or nausea. These effects usually only last for a few moments.
  • You should tell the technologist right away if you feel any breathing difficulties, sweating, numbness, or heart palpitations.
  • Once the scan is done, the table will slide out of the scanner and you will be helped off the table.
  • If an IV line was put in, it will be removed.

While the MRI itself causes no pain, having to lie still for the length of the procedure might cause some discomfort or pain, particularly if you’ve recently been injured or had surgery. The technologist will use all possible comfort measures and complete the procedure as quickly as possible to reduce any discomfort or pain.

What happens after an MRI?
  • Move slowly when getting up from the scanner table to avoid any dizziness or lightheadedness from lying flat for the length of the procedure.
  • If any sedatives were used for the procedure, you may need to rest until the sedatives have worn off. You will also need someone to drive you home.
  • If contrast dye is used, you may be monitored for a period for any side effects or reactions to the contrast dye, such as itching, swelling, rash, or difficulty breathing. If you notice any pain, redness, and/or swelling at the IV site after you go home, tell your doctor as this could be a sign of infection or other type of reaction.
  • Your doctor may give you additional or alternate instructions after the procedure, depending on your particular situation.
  • You can get back to normal activities right away. If you were given contrast, it will pass naturally through your body within a day. You may be told to drink more water or other fluids during this time. 
  • Your doctor will discuss the test results with you during a follow-up appointment or over the phone.