Spotting tumors in dense breast tissue.

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Molecular breast imaging (MBI), a new screening method for breast cancer, identifies tumors in dense tissue that often are not visible with mammography, points out Deborah Rhodes, a researcher at the Mayo Clinic, Rochester, Minn., who helped develop the technology.

MBI overcomes a shortcoming of mammography, which is taken with X-rays. The X-ray imagery does not differentiate between tumors and dense breast tissue. On a mammogram, they both appear white.

"With MBI, a tumor is easy to see, even if it's in dense breast tissue," explains Rhodes. Here's why: with MBI, a woman is given an injection of a short-lived radioactive agent. This material accumulates in tumor cells more than it does in normal cells. Using a radiation-detecting camera, tumors show up as hot spots on the resulting image.

In a Mayo Clinic study comparing MBI with mammography, MBI detected three limes as many cancers in women with dense breast tissue and an increased risk of...