What is magnetic resonance imaging (MRI)?
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.
How is an MRI used to diagnose breast cancer?
MRI may be used to distinguish between benign (non-cancerous) and malignant (cancerous) lesions. 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 better at detecting microcalcifications. The two techniques are used together in screening patients at increased risk for the development of breast cancer. MRI is also commonly used to assess the extent of breast cancer in a woman who has recently been diagnosed with the disease.
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 not seen on mammography or ultrasound.
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.
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 20-45 minutes, during which time several dozen images may be obtained.