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
You may have an MRI scan 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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MRI scans can be harmful if you have metal inside your body, such as:
- Devices likes pacemakers, ear implants, insulin pumps, and shunts
- Joint replacements, plates, or metal pins
- Metal objects or pieces
Make sure your doctor knows of any internal metal before the test.
If you are pregnant or think you may be pregnant, talk to your doctor before the MRI scan about whether this test is right for you.
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.
What to Expect
Prior to Test
Follow your doctor's directions about eating and drinking before the test. This will depend on what part of the body is being viewed.
At the MRI center:
Your doctor may give you a sedative medicine to calm you if you are worried about the test. If your doctor gives you this medicine, you will need to arrange for a ride home. Be sure to follow your doctor's directions on when to take it. This may be 1-2 hours before the exam.
You will be asked:
- Medical and surgical history
- Other problems that you may have—If your MRI scan involves contrast dye, your doctor will ask about the health of your kidneys. There is a risk of problems in people who have kidney disease.
You will be asked if you have something in your body that would cause problems with the MRI scan such as:
- Pacemaker or implantable defibrillator
- Ear implant
- Metal pieces in your eyes or in any other part of your body. Tell your doctor if your work involves metal filings or particles.
- Implanted port device such as an insulin pump
- Metal plate, pins, screws, or staples
- Joint replacement
- Metal clips from aneurysm repair
- Retained bullets
- Any other large metal objects in your body—dental fillings and braces are usually fine
- An x-ray may be taken to check for any metal objects in your body.
- The radiologist will decide if it is safe to have the test.
- You will be asked to remove any metal objects such as, jewelry, hearing aids, or glasses.
- You will also be asked to remove all skin patches that contain medicine. They may contain metal and cause skin burns.
You may be:
- Given ear plugs or headphones. The MRI machine makes a loud banging noise.
- Given an injection of contrast dye into your vein
- Allowed to have a family member or friend with you during the test
Description of Test
If a contrast dye is used, a small plastic IV needle is placed into your hand or arm.
You will lie very still on a sliding table. You may have monitors to track your pulse, heart rate, and breathing. The table will slide into a narrow, enclosed tube. In some machines, the sides are open, so you can look out into the room.
The technician will leave the room. Through the intercom, the technician will give you directions. You can talk to the technician through this intercom. The technician will take the pictures. When the exam is done, you will slide out of the machine. If you have an IV needle, it will be removed.
There are open MRI machines for people who do not like small places or can’t lie on a flat table. There are also machines that let you sit during the test. This may be an option for people with problems, such as painful back.
After the Test
You will be asked to wait while the images are studied. More images may be needed.
If you took a sedative, do not drive, use machinery, or make important decisions until it wears off.
If you are breastfeeding and get contrast dye, you and your doctor should talk about when you should resume breastfeeding. Data has not found any problems to the baby of a breastfeeding mother who has had contrast dye.
How Long Will It Take?
Will It Hurt?
The exam is painless. If you have dye, there may be stinging when the IV needle is placed. You may also feel a slight cooling feeling as the dye is injected.
After the exam, a radiologist will study the images. 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 your doctor if you have:
- Any allergic or unusual symptoms, like getting a rash or swelling if you had contrast dye
- Worsening of symptoms
If you think you have an emergency, call for emergency medical services right away.
NIH Clinical Center
Radiology Info—Radiological Society of North America
Canadian Association of Radiologists
Canadian Radiation Protection Association
Expert Panel on MR Safety, Kanal E, Barkovich AJ, et al. ACR guidance document on MR safe practices: 2013. J Magn Reson Imaging. 2013;37(3):501-530.
Magnetic resonance imaging (MRI)—body. Radiology Info—Radiological Society of North America website. Available at: https://www.radiologyinfo.org/en/info.cfm?pg=bodymr. Updated May 24, 2016. Accessed March 14, 2018.
5/17/2014 DynaMed Plus Systematic Literature Surveillancehttp://www.dynamed.com/topics/dmp~AN~T114252/Routine-prenatal-care: Patenaude Y, Pugash D, Lim K, et al. The use of magnetic resonance imaging in the obstetric patient. J Obstet Gynaecol Can. 2014;36(4):349-355. Available at: https://sogc.org/wp-content/uploads/2014/04/gui306PPG1404E.pdf.
Last reviewed March 2018 by EBSCO Medical Review Board Marcie L. Sidman, MD Last Updated: 5/22/2018