MRIs are conducted with your body stretched out on a flat surface inside a metal tube. "You lie facedown and let your breasts hang through these huge holes," recalls Kim Heier, 42, of Simi Valley, Calif. The hollows in the table contain coils for picking up the MRI's magnetic signal. You may be given an injection of a dye that makes the mass in your breast easier to see.
If you've been diagnosed with breast cancer in one breast, don't be surprised if your doctor suggests an MRI for your other breast. A 2007 study by the American College of Radiology Imaging Network found that for women who'd been diagnosed with cancer in one breast, MRI scans picked up more than 90% of cancers in the opposite (aka contralateral) breast that had been missed by mammography and a clinical breast exam at initial diagnosis.