Magnet Resonance Imaging
Magnetic resonance imaging (MRI) is a technique that uses a magnetic field
and radio waves to create detailed images of the organs and tissues within
Most MRI machines are large, tube-shaped magnets. When you lie inside an
MRI machine, the magnetic field temporarily realigns hydrogen atoms in
your body. Radio waves cause these aligned atoms to produce very faint
signals, which are used to create cross-sectional MRI images — like
slices in a loaf of bread.
The MRI machine can also be used to produce 3-D images that may be viewed
from many different angles.
Why it's done:
MRI is a noninvasive way for your doctor to examine your organs, tissues
and skeletal system. It produces high-resolution images that help diagnose
a variety of problems.
The presence of metal in your body may be a safety hazard or affect a portion
of the MRI image. Before receiving an MRI, tell the technologist if you
have any metal or electronic devices in your body, such as:
- Metallic joint prostheses
- Artificial heart valves
- An implantable heart defibrillator
- A pacemaker
- Metal clips, pins, screws, plates, stents or surgical staples
- Cochlear implants
- A bullet, shrapnel or any other type of metal fragment
- Intrauterine device
Before you schedule an MRI, tell your doctor if you think you're pregnant.
The effects of magnetic fields on fetuses aren't well understood.
Your doctor may recommend choosing an alternative exam or postponing the MRI.
It's also important to discuss any kidney or liver problems with your
doctor and the technologist, because problems with these organs may limit
the use of injected contrast agents during your scan.
How you prepare
Before an MRI exam, eat normally and continue to take your usual medications,
unless otherwise instructed. You will be asked to change into a gown and
- Hearing aids
- Underwire bras
- Cosmetics that contain metal particles
What you can expect
During the test
The MRI machine looks like a tube that has both ends open. You lie down
on a movable table that slides into the opening of the tube. A technologist
monitors you from another room. You can talk with the person by microphone.
The MRI machine creates a strong magnetic field around you, and radio waves
are directed at your body. The procedure is painless. You don't feel
the magnetic field or radio waves, and there are no moving parts around you.
During the MRI scan, the internal part of the magnet produces repetitive
tapping, thumping and other noises. Earplugs or music may be provided
to help block the noise. If you are worried about feeling claustrophobic
inside the MRI machine, talk to your doctor beforehand. You may receive
a sedative before the scan.
In some cases, a contrast material, typically gadolinium, may be injected
through an intravenous (IV) line into a vein in your hand or arm. The
contrast material enhances the appearance of certain details. The material
used for MRIs is less likely to cause an allergic reaction than the material
used for CT scans.
An MRI can last up to an hour or more. You must hold very still because
movement can blur the resulting images.
After the test
If you haven't been sedated, you may resume your usual activities immediately
after the scan.
A doctor specially trained to interpret MRIs (radiologist) will analyze
the images from your scan and report the findings to your doctor. Your
doctor will discuss any important findings and next steps with you.
Call the Diagnostic Imaging Department (815.780.3431) if:
You cannot make it to your MRI appointment on time.
You have questions or concerns about having an MRI.
If you have to take medicine for claustrophobia, call the MRI desk at
815.780.3280 before you take the medicine to make sure we are running on time.