Magnetic resonance imaging (MRI) is a test that produces very clear pictures,
or images, of the human body without the use of X-rays. MRI uses a large magnet,
radio waves, and a computer to produce these images.
MRI to diagnose breast cancer
MRI may be used to distinguish between benign (non-cancerous) and malignant
(cancerous) lesions. Because of its high sensitivity, the MRI may cause
more breast biopsies to be performed. Although MRI can
detect tumors in dense breast tissue, it cannot detect microcalcifications
(tiny specs of calcium), which account for one-half of the cancers detected by
mammography.
Is a MRI examination safe?
Yes. The MRI examination poses no risk to the average patient if appropriate
safety guidelines are followed.
Post-cardiac surgery patients and patients with the following medical devices
can be safely examined with MRI:
- Surgical clips or sutures
- Artificial joints
- Staples
- Cardiac valve replacements (except the Starr-Edwards metallic ball/cage)
- Disconnected medication pumps
- Vena cava filters
- Brain shunt tubes for hydrocephalus
Some conditions may make a MRI examination inadvisable. Tell your doctor if
you have any of the following:
- Heart pacemaker
- Cerebral aneurysm clip (metal clip on a blood vessel in the brain)
- Implanted insulin pump (for treatment of diabetes), narcotics pump (for
pain medication), or implanted nerve stimulators ("TENS") for back
pain
- Metal in your eye or eye socket
- Cochlear (ear) implant for hearing impairment
- Implanted spine stabilization rods
- Severe lung disease (such as tracheomalacia or bronchopulmonary dysplasia)
- Gastroesophageal reflux
In addition, tell the doctor if you:
- Are pregnant
- Weigh more than 300 pounds
- Are not able to lie on your stomach for 30 to 60 minutes
- Have claustrophobia (fear of closed or narrow spaces)
How long is the MRI exam?
Allow 1 hour for your MRI exam. In most cases, the procedure takes
30-45 minutes, during which time several dozen images may be obtained.
Before the exam
Personal items such as your watch, wallet—including any credit cards with
magnetic strips (they will be erased by the magnet)—and jewelry should be left
at home, if possible, or removed prior to the MRI scan. Secured lockers are
available to store personal possessions.
During the exam
You will be asked to wear a hospital gown during the MRI scan.
As the MRI scan begins, you will hear the equipment making a muffled thumping
sound, which will last for several minutes. Other than the sound, you should
experience no unusual sensations during the scanning.
Certain MRI exams require an injection of a contrast material. This helps
identify certain anatomic structures on the scan images.
Please feel free to ask questions. Tell the technologist or the physician if
you have any concerns.
After the exam
Generally, you can resume your usual activities and normal diet immediately.
Your physician will discuss the test results with you.