Mammograms have entered a new dimension, literally. At some screening centers, women are now being offered a 3-D technology that costs more and involves more radiation, but may provide a better look.

The Food and Drug Administration approved the 3-D mammography device last year, and the technique is becoming more common. Radiologists who use 3-D, also known as tomosynthesis, say its drawbacks are worth the greater accuracy.

By itself, 3-D mammography delivers about the same amount of radiation as standard digital 2-D mammograms. But when the FDA approved the new device, it said 3-D could be used only as an add-on to standard mammograms, essentially doubling the low radiation dose.

The FDA made 3-D an add-on only because there is not enough information yet about whether 3-D screenings detect cancers as well as 2-D mammograms do.

"The 3-D image doesn't replace the standard 2-D mammogram," says Julianne Greenberg of Washington Radiology Associates, which has begun telling women who come in for their standard 2-D screening that they can add a 3-D mammogram for $50. "Three-D is added value to an already existing, really good technology."

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When looking at a 2-D and a 3-D image together, radiologists showed a 7 percent improvement in ability to distinguish between cancerous and noncancerous cases, studies show.

More accurate detection reduces the rate of false positives. In the United States, about 10 percent of those who have a mammogram will be called back for additional imaging, the FDA said. The vast majority do not have breast cancer, but they have to cope with the anxiety of perhaps undergoing more invasive testing.

-- The Washington Post