Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) is a painless test that produces detailed images of organs and tissues inside the body without using X-rays. During an MRI, strong magnets and radio waves work together to form images. MRI images may provide more details about a medical condition than X-rays, CT scans, and ultrasounds can provide.

For a standard MRI, you will lie on a table that slides into a tunnel. In an open MRI, the tunnel will be open at the sides. In some cases, dye (contrast material) may be injected into your bloodstream to make the MRI images even clearer.

Tell a health care provider about:

Any allergies you have.
All medicines you are taking, including vitamins, herbs, eye drops, creams, and over-the-counter medicines.
Any surgeries you have had.
Any medical conditions you have.
Any metal you may have in your body. The magnets used in an MRI can cause metal objects in your body to move. Metal can also make it difficult to get clear images. Objects that may contain metal include:
- Any joint replacement (prosthesis), such as an artificial knee or hip.
- An implanted defibrillator, pacemaker, or neurostimulator.
- A metallic ear implant (cochlear implant).
- An artificial heart valve.
- A metallic object in the eye.
- Metal splinters.
- Bullet fragments.
- A port for delivering insulin or chemotherapy.
Any tattoos you have. Some of the darker inks can cause problems with testing.
Whether you are using a birth control implant such as an intrauterine device (IUD).
Whether you are pregnant, may be pregnant, or are breastfeeding.
Any fear of cramped spaces (claustrophobia). If this is a problem, it usually can be managed with medicines given prior to the MRI.

What are the risks?

Generally, this is a safe test. However, problems may occur, such as:

If you have metal in your body and it is close to the area being tested, it may be hard to get high-quality images.
If you are pregnant, you should avoid MRI tests during the first three months of pregnancy. An MRI may affect an unborn baby.
If dye is used:
- You may need to stop breastfeeding until the dye leaves your body naturally, if this applies.
- There is a risk of an allergic reaction to the dye. You can take medicines to prevent this reaction or to treat it if you have allergy symptoms.
- The dye can cause damage to your kidneys. Drinking plenty of water before and after the procedure can help prevent this problem.

What happens before the procedure?

You will be asked to remove all metal, including:
- A watch, jewelry (including jewelry in piercings), and other metal objects.
- Hearing aids.
- Dentures.
- An underwire bra.
- Makeup. Some makeup contains small amounts of metal.
Braces and fillings are normally not a problem.
If you are breastfeeding, ask your health care provider if you need to pump before your test. You may need to stop breastfeeding temporarily if dye will be used.

What happens during the procedure?

You may be given earplugs or headphones to listen to music. The MRI machine can be noisy.
You will lie flat on your back on a long table.
If dye will be used, an IV will be inserted into one of your veins. Dye will be injected into your IV and travel through your bloodstream.
The table will slide into a tunnel that has magnets inside. When you are inside the tunnel, you will still be able to talk to your health care provider.
You will be asked to lie very still while images are taken. Your health care provider will tell you when you can move. You may have to wait a few minutes to make sure that the images produced during the test are clear.
When all images are produced, the table will slide out of the tunnel.

The procedure can last from 30 minutes to over an hour.

The procedure may vary among health care providers and hospitals.

What can I expect after the procedure?

You may be taken to a recovery area if sedation medicines were used. Your blood pressure, heart rate, breathing rate, and blood oxygen level will be monitored until you leave the hospital or clinic.
If dye was used:
- It will leave your body through your urine within a day. You may be told to drink plenty of fluids to help flush the dye out of your system.
- Do not breastfeed your child until your health care provider says that this is safe.

Follow these instructions at home:

You may return to your normal activities right away, or as told by your health care provider.
It is up to you to get your test results. Ask your health care provider, or the department that is doing the test, when your results will be ready.
Keep all follow-up visits. This is important. Talk with your health care provider about what your test results mean.

Summary

Magnetic resonance imaging (MRI) is a painless test that produces detailed pictures of the inside of your body without using X-rays. Strong magnets and radio waves work together to form very detailed and clear images.
In some cases, dye (contrast material) may be injected into your body to make MRI images even clearer.
Before your MRI, be sure to tell your health care provider about any metal you may have in your body.
Talk with your health care provider about what your test results mean.