Stereo Mammography Adds Tool for Finding Breast Cancer

A new radiological diagnostic tool called stereo mammography allows clinicians to detect more lesions and could significantly reduce the number of women who are recalled for additional tests following routine screening mammography.

A 3-D view of breast tissue may provide a more accurate method of detecting breast cancers, say researchers at a recent Radiological Society of North America (RSNA) meeting.

False-positive results [when results incorrectly show a problem] were almost cut in half with stereo digital mammography, says the technology's developer David Getty, Ph.D., a division scientist at BBN Technologies.

"These are women who at the moment are getting a call back from a radiologist saying something suspicious has been found," he explains.

Standard mammography is widely considered to be one of the most difficult exams to read because lesions may be disguised by normal tissue," says Dr. Carl D'Orsi, the director of Emory University's breast imaging center, who conducted the study.

"At the same time, false-positives can also occur because of the two dimensional images provided by the existing technology," he says.

However, after subsequent testing, "most of them are finding out there was nothing there," adds Dr. Getty.

Stereo mammography consists of two digital x-ray images of the breast acquired from two different points of view separated by about eight degrees.

When the images are viewed on a stereo monitor workstation, the radiologist is able to see the internal structure of the breast in three dimensions.

Combining Images Creates Better View

The five-year clinical trial, conducted at Emory University and scheduled to end in December of last year, focused on almost 1,100 women at elevated risk for breast cancer.

Results so far show that that stereo mammography reduced false-positives by 49 percent. The stereoscopic equipment failed to detect 24 out of 109 cancerous lesions, compared to 40 out of 109 lesions not found through standard digital mammography, notes Dr. Getty.

Another advantage of the stereoscopic digital mammography is that it "is much better at picking up cluster calcifications [that] can be associated with malignancy," adds Dr. Getty.

This technology also allows radiologists to get a picture of the entire breast volume in a slice-by-slice view.

"It certainly helps, because you're seeing all of the tissue in depth," says Dr. Getty.

The capacity of mammography to detect problems in dense breasts is not an issue with the stereoscopic digital equipment because it "doesn't look as dense, because tissue is being spread out in depth," he says.

A stereoscopic mammogram image works on principles similar to the old View-Master® slide viewers used by children, explains Dr. Getty.

Each of two images inserted in the View Master were channeled to a different eye, and the brain's "visual cortex - the magician in all this - then combines the two images, artificially recreating what your two eyes normally create when you walk around in a three-dimensional world."

Similarly, the viewing monitor for stereo mammography merges two distinct images to create a 3-D look at tissue.

Technology on the Horizon May Improve

Experts say stereo mammography does show promise, but more work is needed.

"Stereo mammography is a step in the right direction, but it is not a breakthrough," says Dr. David Bluemke, at Johns Hopkins Medical Institutions in Baltimore, Md. "True 3-D tomographic imaging of the breast is ultimately needed."

By giving the radiologist a view of slices through the breast, 3-D tomography would allow the radiologist to see lesions that are otherwise obscured by being superimposed on normal breast tissue, he explains.

Stereoscopic digital mammography "seems very promising," adds Dr. Kristin Byrne, chief of breast imaging at Lenox Hill Hospital in New York City. "It would make mammography that much better."

With current technology, the problem of calling back a woman whose breasts show a suspicious area is that radiologists often cannot find that same suspicious tissue in a second view, so the woman has to follow-up with further monitoring in another six months or have a biopsy.

According to Dr. D'Orsi, increasing the use of stereo mammography at many institutions across the country would require simple upgrades to existing digital mammography equipment and software.

The stereo digital exam currently takes the same amount of time to read as a standard mammogram, and researchers are working toward making radiation exposure in stereo scans comparable.

Always consult your physician for more information.