Magnetic resonance imaging (MRI) is a type of safe, painless testing that doctors
use to see the body's organs and structures. MRI uses a magnetic field and radio waves
to create detailed pictures of the body's insides. Unlike CAT scans or X-rays, MRI
doesn't use radiation.
An MRI scanner is a large doughnut-shaped magnet that often has a tunnel in the
center. You lie on a table that slides into the tunnel. Some hospitals and radiology
centers use what are called "open" MRI machines. They have larger openings and are
helpful for people who are afraid of being in tight, closed-in spaces.
Why Do You Need It?
MRI helps in several ways:
It gives clear images of body parts that can't be seen as well with an X-ray,
CAT scan, or ultrasound. MRI is helpful for looking at a person's eyes, ears, heart,
and circulation system. It also helps doctors see inside joints, cartilage, ligaments,
MRI lets doctors detect problems in the brain, spinal cord, skeleton, chest, lungs,
abdomen, pelvis, wrists, hands, ankles, and feet.
It helps doctors identify infections and conditions that cause swelling inside
It allows doctors to see when there isn't a problem
inside the body — like a tumor, for example. Doctors call this "ruling
out" a condition.
Preparing for Your MRI Exam
You don't usually need to do anything special (like fasting) before an MRI
exam. Because metal can leave a bright or blank spot on the MRI film, you will need
to take off anything you're wearing that has metal in it (like glasses, jewelry, or
belts) before you lie on the MRI table.
A specially trained technician (or "tech") operates the MRI machine. He or she may
ask if you have any metal clips from surgery or anything else that's metal inside
your body. These things might cause a problem near the strong magnetic field.
You won't be able to take your music player or other devices into the MRI
room. Electronics can interfere with the equipment.
Some people are given medicine so they fall asleep (called "sedation") during an
MRI exam. Sedation is usually used for infants and little kids who can't stay still
during MRI. Sometimes MRI techs sedate teens who have trouble relaxing inside the
If you need sedation, your doctor will ask you not to eat or drink for several
hours before the MRI. Before you get sedation, tell the MRI tech if you:
have every had a bad reaction to medicines
might be pregnant
An MRI exam usually takes between 20 and 90 minutes. How
long you stay in the machine depends on the type of study your doctor has ordered
and whether the tech needs to re-do any scans.
You'll lie on the scanning table. The technician will
move you into position. When you're ready, the table slides into the tunnel and the
tech takes the images. Each scan lasts a few minutes.
Some people get a contrast solution as part of an MRI exam. Contrast solution
is a liquid that goes inside the body to highlight things like blood vessels. It helps
doctors see specific problems that might not show up otherwise.
If you need contrast solution, the tech will probably use an IV to get it inside
your body. He or she will ask if you're allergic to any medicines or food before
giving you contrast solution.
If you feel cold lying on the MRI table, ask for a blanket before the test
starts. You'll need to stay still during the actual MRI so that the images come out
clearly. If an image is blurred, it may need to be done over.
The noises that an MRI machine makes can be loud! You can't bring your own
player into the MRI room, but some places give you special headphones so you can listen
The headphones also let you talk to the technician. If an MRI system doesn't have
headphones, it may have an intercom so the technician can talk to you and tell you
what to do during the test. Some machines have a call button that you can press if
you need help.
When the exam is over, the technician will help you off the table. If you've been
sedated, the tech will wheel the table to a recovery area and you'll stay there
until you're ready to stand up.
After the test, you'll probably be able to go back to your normal routine right
away. Most sedation wears off in 1-2 hours. Any contrast material should be gone from
your body in about 24 hours.
MRIs are safe and easy. Because they use low-energy radio waves instead of radiation,
doctors haven't found any health risks. People can get more than one MRI with no side
Because MRI techs ask questions before giving people sedation or contrast solution,
it's very rare to have an allergic reaction. If someone does have a reaction, the
technician and other staff are trained to handle it.
If you have kidney problems, tell the radiologist and technician before
they give you IV contrast solution. In very rare cases, people whose kidneys
don't work well can have problems after getting contrast solution.
Getting Your Results
You won't get MRI results right away. A radiologist (a doctor trained to understand
MRI scans) needs to look at the images. The radiologist will send a report to your
doctor. Your doctor will then call or make an appointment to talk to you about the
results and explain what they mean.