An MRI uses magnetic waves and computers to make pictures of the inside of the body. It can make two-dimensional and three-dimensional pictures.
You may have an MRI to diagnose a condition or look for internal injuries. MRIs can look at any body part, from your head to your toes. MRIs can also be used to see if medication or treatment is working for a specific disease like cancer.
MRI of Brain Injury
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MRIs can be harmful if you have metal inside your body including:
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 an MRI scan is right for you.
A contrast dye may be used to enhance some images. Some people may have a bad reaction to this dye. Talk to your doctor about any allergies you have or if you have liver or kidney problems. Liver and kidney problems may make it difficult for your body to get rid of the contrast.
Follow your doctors instructions regarding eating and drinking before the test. This will depend on what part of the body is being examined.
At the MRI center:
Your doctor may give you a medication to calm you if you are anxious about the test. If your doctor prescribes a sedative you will need to arrange for a ride home. Be sure to follow your doctor's instructions on when to take the sedative. It may need to be taken 1-2 hours before the exam.
You may be:
If a contrast dye is used, a small IV needle is inserted into your hand or arm.
You will lie very still on a sliding table. Depending on your condition, you may have monitors to track your pulse, heart rate, and breathing. The table will slide into a narrow, enclosed cylinder. 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 as well. 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.
If you are claustrophobic or unable to lie on a flat table, there are open MRI machines available. They allow you to have the test done without being put in a narrow cylinder. There are also MRI machines that allow a patient to be in a sitting position. This may be important for patients with concerns, like a painful back.
You will be asked to wait at the facility while the images are examined. The technician may need more images.
If you took a sedative, do not drive, operate machinery, or make important decisions until it wears off completely.
If you are breastfeeding and receive a contrast dye, you and your doctor should discuss when you should resume breastfeeding. Information available has not found any ill effects to the baby of a breastfeeding mother who has had contrast dye.
The exam is painless. If you have dye injected, there may be stinging when the IV needle is inserted. You may also feel a slight cooling sensation as the dye is injected.
After the exam, a radiologist will analyze the images and send a report to your doctor. Your doctor will talk to you about the results and any further tests or treatment.
NIH Clinical Center
RadiologyInfo—Radiological Society of North America, Inc.
Public Health Agency of Canada
Hailey D. Open magnetic resonance imaging (MRI) scanners. Issues Emerg Health Technol. 2006 Nov;(92):1-4.
Kanal E, Barkovich A.J., et al. ACR Guidance Document for Safe MR Practices: 2013. J Magn Reson Imaging. 2013;37(3):501-530.
Magnetic resonance imaging (MRI)—body. Radiology Info—Radiological Society of North America, Inc. website. Available at: http://www.radiologyinfo.org/en/info.cfm?pg=bodymr. Updated February 12, 2014. Accessed January 26, 2015.
1/4/2011 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed: US Food and Drug Administration. New warnings required on use of gadolinium-based contrast agents. US Food and Drug Administration website. Available at: http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm225286.htm. Updated September 9, 2010. Accessed January 26, 2015.
5/17/2014 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed: Patenaude Y, Pugash D, et al. The use of magnetic resonance imaging in the obstetric patient. J Obstet Gynaecol Can. 2014 Apr;36(4):349-355. Available at: http://sogc.org/wp-content/uploads/2014/04/gui306PPG1404E.pdf. Accessed January 26, 2015.
Last reviewed January 2015 by Michael Woods, MD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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