How Are Ultrasound & MRI Scans Used to Diagnose Breast Cancer?
In addition to mammography, two screening tools that may be used to view the breast tissue are ultrasound and magnetic resonance imaging (MRI).
Ultrasound is an imaging technique that uses sound waves to produce a picture. Breast ultrasound may be used to further evaluate a lump found by the patient or her doctor or to evaluate an abnormal finding from a mammogram. Ultrasound can help differentiate between a fluid-filled lump (such as a harmless cyst) or a solid lump. If the lump is determined to be solid, additional tests (like a biopsy) may be needed, as an ultrasound cannot distinguish between a cancerous solid lump and a non-cancerous solid lump.1,2
During a breast ultrasound, the patient is asked to undress from the waist up and given a gown to wear. The sonographer or radiologist will use a gel on the skin of the breast to help the ultrasound wand (called a transducer) glide and to improve the conduction of the sound waves through the tissue. The test is generally painless unless the lump itself is tender. The lights in the room may be dimmed to help the sonographer see the screen, on which black and white images of the breast tissue will be viewable. In addition to the breast, the ultrasound may also be used to view the lymph nodes under the arm, called the axillary lymph nodes. A special type of ultrasound, Doppler ultrasound, may also be used to view potential blood flow to the lump or abnormal area in the breast.1,2
Ultrasound may also be used to help guide a needle for a needle biopsy, in which small amounts of the tissue are removed to be examined under a microscope. In some cases, ultrasound may also be used as a screening technique (in women who are not having symptoms of breast cancer), such as women who are pregnant and cannot be exposed to x-rays from a mammogram or women who have dense breast tissue.1
MRI is an imaging test that uses powerful magnets and radio waves to generate pictures of the internal structures of the body. An MRI can produce detailed images of the structures within the breast and may be used on the breast to further evaluate abnormalities found on a mammogram, to screen women who are at high risk for breast cancer, or to determine the extent of a diagnosed breast cancer. MRI is also the best technique to determine if a breast implant has ruptured.3
Because an MRI uses magnets, patients should tell their technician about any medical devices or implants. (Orthopedic implants, like those used in joint replacements, are usually fine, but should still be mentioned to the technician before the MRI.) Patients are asked to remove all jewelry and wear a gown during the MRI. An MRI is typically not painful, but it may cause claustrophobia or anxiety as the body lays on a movable table that slides into the machine. Some people may find it helpful to talk to their doctor about potentially getting a prescription for a mild sedative before the exam.3
During a breast MRI, the patient lays face down with the breasts fitting into a hollow depression. While the MRI machine is running, it is normal to hear tapping and thumping noises. These can be loud, and the patient may receive earplugs to wear during the MRI.4