What is an MRI?

female physician looks at mri scans on computer screens

The MRI machine is a large, tube-shaped machine that uses a large magnet, radiofrequencies, and computers to form two-dimensional (2D) images of the body area being studied. Cross-sectional views can be done to show more details. MRI does not use radiation, like X-rays or computed tomography (CT scans), and may be used instead of a CT scan when organs or soft tissue are being studied. An MRI may be done with or without “contrast.” Contrast refers to a substance taken by mouth or injected into an intravenous (IV) line that causes the particular organ or tissue under study to show up more clearly on the scan.

Who cannot undergo an MRI?

What information should you share before an MRI?

What happens during an MRI?

An MRI may be done on an outpatient basis or as part of your stay in a hospital. Generally, an MRI scan follows this process:

You will be asked to remove any clothing, jewelry, eyeglasses, hearing aids, hairpins, removable dental work, or other objects that may get in the way of the procedure.
If you are asked to remove clothing, you will be given a gown to wear.
If you are to have an MRI with contrast, an intravenous (IV) line will be started in your hand or arm for injection of the contrast dye.
You will lie on a narrow table that slides into the large circular opening of the scanning machine. Pillows and straps may be used to help prevent movement during the scan.
The technologist will be in another room where the scanner controls are located. However, you will be in constant sight of the technologist through a window. Speakers inside the scanner allow technologist to talk to you and hear you. You will have a call button so that you can let the technologist know if you have any problems during the procedure. The technologist will be watching you at all times and will be in constant communication.
You will be given earplugs or a headset to wear to help block out the noise from the scanner. Some headsets may provide music for you to listen to. During the scanning process, you will hear clicking and thumping noises as the magnetic field is created and pulses of radio waves are sent from the scanner.
It will be important for you to stay very still during the exam. Any movement could cause distortion and affect the quality of the scan.
At intervals, you may be told to hold your breath, or to not breathe for a few seconds. You will then be told when you can breathe. You should not have to hold your breath for longer than a few seconds.
If contrast dye is used, you may feel some effects when the dye is injected into the IV line. These effects include a warm flushing sensation or a feeling of coldness, a salty or metallic taste in the mouth, a brief headache, itching, or nausea. These effects usually only last for a few moments.
You should tell the technologist right away if you feel any breathing difficulties, sweating, numbness, or heart palpitations.
Once the scan is done, the table will slide out of the scanner and you will be helped off the table.
If an IV line was put in, it will be removed.
While the MRI itself causes no pain, having to lie still for the length of the procedure might cause some discomfort or pain, particularly if you’ve recently been injured or had surgery. The technologist will use all possible comfort measures and complete the procedure as quickly as possible to reduce any discomfort or pain.
On occasion, some people with metal fillings in their teeth may experience some slight tingling of the teeth during the procedure.

How do I find out my test results?