Magnetic Resonance Imaging
(Imaging, Magnetic Resonance; MRI Scan; MRI)
An MRI scan uses magnetic waves and computers to make pictures of the inside of the body. It can make 2- and 3-dimensional pictures.
Reasons for Test
An MRI scan may be done to diagnose a problem or look for injuries. MRI scans can look at any body part. They can also be used to see if medicine or treatment is working for a disease.
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Problems are rare, but all procedures have some risk. The doctor will go over some problems that could happen. For example, MRI scans can be harmful in someone who has metal inside the body, such as:
- Devices likes pacemakers, ear implants, insulin pumps, and shunts
- Joint replacements, plates, or metal pins
- Metal objects or pieces
A contrast dye may be used to take clearer pictures. Some people may have a reaction to this dye. Talk to your doctor about any allergies you have. Tell your doctor if you have liver or kidney problems. These problems may make it hard for your body to get rid of the dye.
Pregnant women should talk to their doctors about the risks of having an MRI scan.
What to Expect
Prior to Test
The staff may meet with you to talk about:
- Anesthesia that may be used
- Any allergies you may have
- Current medicines, herbs, and supplements that you take and whether you need to stop taking them before the scan
- Whether you have something in or on your body that would cause problems with an MRI, such as a medical device, joint replacement, or metal object
- Fasting before the scan, such as avoiding food or drink
- Whether you need a ride to and from the scan
- Tests that will need to be done before the scan, such as an x-ray to check for metal objects in the body
Certain people may be given:
- Sedation—you will be relaxed
- General anesthesia—you will be asleep
Description of Test
The MRI machine makes a loud banging noise. You may be given ear plugs or headphones before the scan.
A contrast dye may be injected into your hand or arm. You will lie very still on a sliding table. Monitors may be used to track your pulse, heart rate, and breathing. The table will slide into a narrow, enclosed tube.
The technician will leave the room. You will be given directions through an intercom. You can reply through the intercom. The pictures will be taken. You will exit the machine. Any IV needles used will be removed.
How Long Will It Take?
40 to 90 minutes
Will It Hurt?
The exam is painless.
The images will be studied. A report will be sent to your doctor. Your doctor will talk to you about the results and any further tests or treatment.
Call Your Doctor
Call the doctor if you have:
- Any allergic symptoms, such as a rash or swelling if contrast dye was used
- Problems urinating
- Nausea or vomiting
- Worsening of symptoms
If you think you have an emergency, call for medical help right away.
NIH Clinical Center
Radiology Info—Radiological Society of North America
Canadian Association of Radiologists
Canadian Radiation Protection Association
Magnetic resonance imaging (MRI)—body. Radiology Info—Radiological Society of North America website. Available at: https://www.radiologyinfo.org/en/info.cfm?pg=bodymr. Accessed August 18, 2020.
National Institute for Health and Care Excellence (NICE). Prostate cancer: diagnosis and treatment. NICE 2019 May:NG131.
Prostate cancer diagnosis and staging. EBSCO DynaMed website. Available at: https://www.dynamed.com/evaluation/prostate-cancer-diagnosis-and-staging. Accessed August 18, 2020.
Last reviewed March 2021 by EBSCO Medical Review Board James P. Cornell, MD Last Updated: 3/3/2021