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Listen to the Cancer.Net Podcast: MRI–What to Expect, adapted from this content.
Magnetic resonance imaging (MRI) is a diagnostic examination that uses magnetic fields to create detailed, computer-generated pictures of internal organs and tissue, including the brain and spinal column. An MRI scan is often used to diagnose and evaluate tumors in the chest and abdomen. For example, this test may better identify a small mass within a woman's breast than a mammogram or ultrasound, particularly for women with very dense breast tissue. And, because it does not use radiation, it is frequently chosen as a diagnostic tool for the female and male reproductive systems.
The medical team
An MRI is performed at the radiology department of a hospital or at an outpatient imaging center. It is performed by a radiologist (a medical doctor who performs and interprets imaging tests to diagnose disease) or a radiology technologist who is specially trained and certified to perform, but not interpret, MRI scans.
Questions to ask your doctor
Before having an MRI, consider asking your doctor the following questions:
- Who will perform the MRI?
- What will happen during the MRI?
- How long will the procedure take?
- Can a friend or family member sit in the MRI room during my examination?
- What are the risks and benefits of having an MRI?
- Is the imaging facility accredited to perform MRIs?
- When will I learn the results?
- Who will explain the results to me?
- What further tests will be necessary if the test results indicate cancer?
Preparing for the procedure
When you schedule your MRI, you will get detailed instructions on how to prepare.
You may need to avoid eating for two or more hours before the examination, but generally you will not need to make any special preparations.
Tell your doctor about all medications you are taking, as well as any drug allergies or other medical conditions you have. Women should tell their doctors if there is any chance that they are pregnant.
In addition, it is important to tell your doctor and the technologist performing your MRI about any metal implants or metal fragments you have in your body. These can cause serious, and even fatal, complications when exposed to the strong magnetic pull generated by the MRI. People with pacemakers, for example, cannot have an MRI.
You will be asked to sign a consent form that states you understand the benefits and risks of the MRI and agree to have the test done. Talk with your doctor about any concerns you have about the MRI.
Also consider asking whether you can bring music with you to the scan; some facilities allow patients to listen to music through headphones during the examination.
During the procedure
When you arrive for your MRI, you will need to remove any jewelry or other metal objects you are wearing. You may need to change into a hospital gown, as well.
Depending on the part of your body to be scanned, you may be given a contrast material (a special dye) called gadolinium through an intravenous (IV) line. A nurse or doctor will insert a small needle into a vein in your arm or hand; saline solution will flow through the line until the contrast material is injected at a specific point during the examination. The dye will travel through your bloodstream and help to create a clearer picture of specific parts of your body.
A technologist will help position you on a moveable exam table outside of the MRI machine. You will lie on your back with your arms at your side and your head on a headrest. A “coil” will be positioned over or around the part of your body that will be studied to create a clear picture of that area.
When you are in the correct position, the table will slide into the MRI machine, which resembles a large donut. The standard MRI machine has a narrow, tunnel-like opening. Some facilities have less confining “short-bore” or “open” MRI machines.
The exam table will slide through the hole in the center of the machine. You will need to lie still during the MRI's two-to-six imaging sequences. Each sequence will last up to 15 minutes. You will know that the machine is taking images because you will hear loud tapping or knocking sounds. The part of your body that is being examined may feel warm during the MRI; this is normal.
An MRI is not painful. However, if you receive an IV, you may feel discomfort when the needle is inserted, and the saline solution in the IV may cause a cool feeling at the injection site. In addition, you will need to lie still for most of the scan, which could become uncomfortable. The loud sounds coming from the machine may also make you uncomfortable; you may be given earplugs to wear during the examination. Meanwhile, if you are claustrophobic, tell the technologist before beginning the examination. The radiologist may be able to give you a sedative to help you relax.
During the examination, the technologist will be in a nearby computer room, separated by a window. The technologist will be able to see you, and you will be able to communicate at all times through an intercom system.
The MRI will last up to 90 minutes. The technologist should be able to give you a time estimate before you begin.
When the MRI is complete, you may be asked to remain on the exam table while a radiologist reviews the images to determine if additional images are needed.
After the procedure
You can expect to resume your normal activities immediately after your MRI, including driving, unless you've been given a sedative.
Last Updated: February 23, 2011