New technique: 3-D breast tomosynthesis may improve cancer detection.(Gynecology)

NEW ORLEANS -- Breast tomosynthesis, a new three-dimensional extension of conventional mammography, has the potential to improve detection of breast cancers while reducing the rate of false-positive findings, Dr. Elizabeth Rafferty reported at the annual meeting of the American Society of Clinical Oncology.

The technique employs conventional mammographic x-ray tubes and digital imaging plates, but the x-ray source is movable, and swings over the breast in a 50-degree arc, creating 11 discrete images that can be combined or analyzed in many different ways, explained Dr. Rafferty, a radiologist at the Avon Foundation Comprehensive Breast Evaluation Center, Massachusetts General Hospital, Boston.

The hospital has been developing this technology for several years, and is the only facility in the country with an apparatus designed for breast tomosynthesis. However, the center has licensed the technology to General Electric, which will likely launch tomosynthesis equipment for wider use within the next 18 months. Hologic/Lorad is also working on tomosynthesis technology.

According to Dr. Rafferty, there is no doubt that conventional screening mammography has improved early detection and treatment of breast cancer, resulting in an overall 50% decrease in mortality. Still, approximately 20% of all breast cancers are found in women who have had a screening mammogram in the prior 12 months. In the vast majority of cases, these cancers were not unusually fast growing, but were masked or undetectable with conventional mammographic technology.

The accuracy of standard mammography is limited by the fact that a three-dimensional structure is represented in a single two-dimensional image. A lot of "structured noise" is created by the overlap of normal radiographically dense structures. This overlap can obscure existing neoplastic tissue, and also can create the illusion of a lesion where no true lesion is present.

Many breast cancer specialists believe magnetic resonance imaging is a far better tool than mammography for detecting breast cancers, and there is considerable data to show that it gives much greater accuracy. However, the cost of MRI, the relatively small number of centers that can offer it, and the inconvenience it imposes on patients make it impractical as a first-line screening tool.

Though it is still too early to tell where breast tomosynthesis will fit into the pecking order of breast cancer screening techniques, it certainly has great potential. Dr. Rafferty said it creates a strong platform for digital subtraction angiography, and described the device as "the poor woman's MRI."