Breast magnetic resonance imaging (MRI) uses magnetic fields to create a three-dimensional image of the breast. A contrast agent is given through an IV during the procedure. At this time, breast MRI is mostly used to assess the extent of disease in a patient who is diagnosed with breast cancer, and in breast cancer screening for women who are at increased risk. There is no radiation involved.
Close surveillance or screening for cancer uses tests to try to detect cancer in its early stages, when it is most treatable. The American Cancer Society recommends that women with a high risk of breast cancer undergo MRI screening in addition to mammography, as MRI is more sensitive in detecting the disease.
Because of its high sensitivity, MRI may also pick up areas of the breast that attract blood flow but are not cancerous, leading to "false positives" and unnecessary biopsies. Although MRI can detect tumors in dense breast tissue, mammography is still the only test that shows microcalcifications, which may be the earliest sign of breast cancer. The two techniques are used together in screening patients at increased risk for developing breast cancer.
MRI is also commonly used to measure the extent of breast cancer in women who have recently been diagnosed with the disease, particularly in:
Women with mammographically dense breast tissue;
Suspected disease in more than one part of the breast, or in both breasts, or;
Cases of invasive lobular breast cancer which may be difficult to assess mammographically.
Because MRI is still a relatively expensive test, it is important to see if the test will be covered by insurance, a process called "pre-authorization." Further, not all facilities have MRI machines specifically made for imaging the breast, or radiologists capable of interpreting breast MRI results. A center should have the capability of performing MRI-guided biopsies to sample areas of concern that are not seen on mammography or ultrasound.
Some conditions may make a MRI examination inadvisable. Tell your doctor if you have any of the following:
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)
In addition, tell the doctor if you:
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 20-45 minutes.
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 before 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 have no unusual sensations during the scanning.
To have a breast MRI exam, you will receive an injection of a contrast material called gadolinium. Patients who have poor kidney function should not receive gadolinium.
Please feel free to ask questions. Tell the technologist or the physician if you have any concerns.
After the exam
You can resume your usual activities and normal diet immediately.
Your doctor will discuss the test results with you.
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