The Basics
Magnetic resonance imaging (MRI) is a non-invasive medical test that uses magnetic field and radio wave energy to create detailed images of organs and structures inside the body. This test is performed when a doctor needs to see cross-sectional images of the inside of the body to detect problems with the body that other methods may not be able to determine.
The MRI test can identify a number of health problems such as injury, tumors, infections, bleeding, blood clots, and blood vessel problems. It can also detect damage to the head, nerves, heart, lung, reproductive system, liver, bladder, pancreas, kidney, bones, joints, and spine.
Sometimes, you may be asked to take a special dye (also called contrast material, contrast dye, or contrast medium) to make images of the problematic areas clearer. Your doctor will determine whether this test is needed.
Risks and precautions
There is a small risk of developing allergic reactions to the contrast material used in the test. Therefore, it is crucial to tell your health care provider if you have any allergies. In addition, there is also a small risk that the injection site for the contrast material may become infected.
There are no known harmful effects of the magnetic field used for the MRI. However, there is limited information on the effects of MRI on unborn babies. Therefore, you should tell your doctor or the person performing the test if you are or may be pregnant.
The magnet can damage metal objects. You should remove any unsecured metal objects such as watches or jewelry. People that carry certain medical devices may not be able to undergo an MRI scan, or they may have to take extra precautions to avoid problems. It is crucial to tell the technologist if you carry any of them. Examples of such devices may include but are not limited to:
- artificial heart valve
- artificial limb
- braces
- body piercing
- cochlear implant
- hearing aid
- dental implant
- intrauterine device
- iron pigments in tattoos or "permanent makeup"
- medications in the form of a patch
- metallic joint prostheses
- metal pins, screws, plates, stents
- metal parts in the eyes
- nerve stimulators
- other medical devices (e.g., medication infusion pump)
- pacemakers
It is important that you understand all the risks of complications and side effects of the test, and what you or your doctor can do to avoid them. Make sure that your doctor is aware of all your concerns.
Before the test
It is important that you fully understand what the test involves beforehand. Ask your doctor to explain the risks, benefits, and drawbacks of the test, and don't be shy to probe further until you are comfortable with your doctor's responses.
Tell your doctor or MRI technologist if you:
- are allergic to any medications, especially contrast material
- are or might be pregnant
- are uncomfortable in small spaces
- carry any metal devices on your body (as mentioned above)
- had recent surgery on blood vessels
- have any medical conditions (people with certain conditions should not use the MRI test dyes)
- worked around metal (you may have small metal fragments in your body)
You will need to remove all metal objects including hearing aids, dentures, jewelry, and hairpins. Otherwise, these objects will be attracted to the powerful magnet used during the MRI and cause damage. You may be asked to not eat or drink a few hours before the test, depending on the body part being examined.
If you are taking any prescription or over-the-counter (non-prescription) medications, supplements, or herbal products, make sure you inform your doctor or pharmacist. Ask them whether it is necessary for you to stop taking any of these medications and products before the test. It is also important to tell them if you have allergies to certain medications or have certain medical conditions.
Plan to have someone drive you home after the test.