3-D mammography cuts false-positive rates by half

CHICAGO (Reuters Health) - Stereoscopic digital mammography, which gives a 3-dimensional view of the inner structures of the breast, cuts the number of falsely diagnosed tumors in half, compared with conventional mammography, researchers reported here this week.

Preliminary results with stereoscopic digital mammography were described at the meeting of the Radiological Society of North America by one of its developers, Dr. David J. Getty of BBN Technologies of Cambridge, Massachusetts.

The technique involves capturing two images 6 to 10 degrees apart that are cross-polarized and then superimposed, in much the same way as two images are used to create 3-D movies.

"Two-dimensional imaging masks subtle lesions," Getty explained. "With 3-D mammography, this is greatly reduced. Lesions can be seen as lying at different depths."

In the study, 1,093 women referred for evaluation of suspected breast cancer were each examined with conventional mammography and the stereoscopic digital technique.

There were 259 abnormalities detected with one or both approaches, with 109 true positives and 150 false positives. Compared with conventional mammography, stereoscopic digital imaging reduced the false-positive rate by 49 percent.

"A 15 percent drop would have been a significant reduction, so this is a highly statistically significant finding," Getty said. "It cuts the false-positive rate in half, resulting in fewer patient recalls, less anxiety and less cost."

Data on approximately 1500 women are expected to be analyzed by the end of the year, at which point the trial will be complete.