An MRI (magnetic resonance imaging) scan is an imaging test that uses powerful magnets and radio waves to create pictures of the body. It does not use radiation (x-rays).
Single MRI images are called slices. The images can be stored on a computer or printed on film.
One exam produces dozens or sometimes hundreds of images.
How the Test is Performed
You may be asked to wear a hospital gown or clothing without zippers or snaps (such as sweatpants and a t-shirt). Certain types of metal can cause blurry images.
You will lie on a narrow table, which slides into a large tunnel-shaped scanner.
Some exams require a special dye (contrast). Most of the time, the dye will be given through a vein (IV) in your hand or forearm before the test. The dye helps the radiologist see certain areas more clearly.
Small devices, called coils, may be placed around the head, arm, or leg, or other areas to be studied. These help send and receive the radio waves, and help the quality of the images.
During the MRI, the person who operates the machine will watch you from another room. The test lasts about 30 to 60 minutes, but may take longer.
How to Prepare for the Test
Tell your doctor if you are afraid of close spaces (have claustrophobia). You may be given a medicine to help you feel sleepy and less anxious, or your doctor may suggest an "open" MRI, in which the machine is not as close to the body.
Before the test, tell your health care provider if you have:
- Artificial heart valves
- Brain aneurysm clips
- Heart defibrillator or pacemaker
- Inner ear (cochlear) implants
- Recently placed artificial joints
- Vascular stents
- Worked with sheet metal in the past (you may need tests to check for metal pieces in your eyes
- Kidney disease or dialysis (you may not be able to receive contrast)
Because the MRI contains strong magnets, metal objects are not allowed into the room with the MRI scanner:
- Items such as jewelry, watches, credit cards, and hearing aids can be damaged.
- Pens, pocketknives, and eyeglasses may fly across the room.
- Pins, hairpins, metal zippers, and similar metallic items can distort the images.
- Removable dental work should be taken out just before the scan.
If you are over the age of 65 or have any kidney problems or diabetes you will need to obtain a creatinine level (lab work) at least one day before your scheduled exam date.
How the Test Will Feel
An MRI exam causes no pain. If you have difficulty lying still or are very nervous, you may be given a medicine to relax you. Too much movement can blur MRI images and cause errors.
The table may be hard or cold, but you can request a blanket or pillow. The machine produces loud thumping and humming noises when turned on. You can wear ear plugs to help reduce the noise.
An intercom in the room allows you to speak to someone at any time. Some MRIs have televisions and special headphones that you can use to help the time pass.
There is no recovery time, unless you were given a medicine to relax. After an MRI scan, you can resume your normal diet, activity, and medications.
Why the Test is Performed
Having MRIs with other imaging methods can often help your doctor make a diagnosis.
MRI images taken after a special dye (contrast) is delivered into your body may provide extra information about the blood vessels.
An MRA, or magnetic resonance angiogram, is a form of magnetic resonance imaging, that creates three-dimensional pictures of blood vessels. It is often used when traditional angiography cannot be done.
MRI does not use ionizing radiation. No side effects from the magnetic fields and radio waves have been reported.
The most common type of contrast (dye) used is gadolinium. It is very safe. Allergic reactions rarely occur. However, gadolinium can be harmful to people with kidney problems who are on dialysis. Tell your health care provider before the test if you have kidney problems.
The strong magnetic fields created during an MRI can cause heart pacemakers and other implants not to work as well. The magnets can also cause a piece of metal inside your body to move or shift.
We are located at Adventist Health St. Helena
10 Woodland Road
St. Helena, CA 94574
Please check in at the admissions office. Walk into the front entrance of the medical center and turn left at the front desk. Follow signs for admissions.
To learn more, please call us at (707) 963-6570