The emergence of magnetic resonance as a viable imaging tool for evaluating the breast presents new diagnostic possibilities for ob/gyns. But before you can use it wisely, you have to understand certain key clinical parameters, recognize the technical factors that affect the quality of breast MR images, and be familiar with current indications for the procedure.
Today's ob/gyns have several technologies available to capture images of a woman's breast. Mammography is the only approach proven to reduce mortality from breast cancer, by approximately 30%.1-3 These images can be acquired digitally or on conventional film-screen. Digital mammography is equivalent to conventional film-screen and apparently doesn't offer any significant clinical advantages, except that the images are less likely to be misplaced or lost.4-6
Ultrasound (U/S) is currently reserved for the evaluation of a palpable abnormality that has been detected on physical examination, for persistent focal area of breast pain, or for focal mammographic findings. Although preliminary evidence suggests that U/S may be valuable in screening women with dense breast tissue, it has not been shown to reduce mortality in any large, prospective screening study.7,8
Positron emission tomography (PET) uses radioactive 18fluorine-labelled glucose to detect breast malignancies; unfortunately its relatively low sensitivity of 60% limits its usefulness as a screening tool. It's most useful in detecting recurrent or metastatic breast cancer and possibly monitoring response to chemotherapy.9,10 With a sensitivity of 30% to 80% depending on tumor size, Sestamibi nuclear imaging is not very useful for breast imaging at this time.11,12
The history of MR imaging Research on MR for the detection and diagnosis of breast disease began in the late 1980s, initially focusing on the detection of silicone implant ruptures.15,16 At the time, there was a great deal of speculation on the possible link between free silicone and connective tissue disease-which later proved unfounded.
Since the early 1990s, with the addition of intravenous gadolinium, scientists recognized that they could see through dense tissue and study the neovascularity associated with breast malignancies.17,18 By the late 1990s, many tertiary cancer centers began to routinely use MR imaging for selected women with breast cancer, and more recently, for screening known carriers of the BRCA-1/2 genes.13,14,19-26
Despite all these advances, we still don't know what the false-negative rate of breast MR imaging is. Although it's a very sensitive tool for detecting invasive carcinoma, it does not avoid the need for biopsy of a suspicious clinical or imaging finding.27
Getting the most outof breast MR imaging To maximize the clinical value of breast MR imaging, physicians must understand several clinical and technical issues.