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.
Mammograms are probably the most important tool doctors have to help them diagnose, evaluate, and follow women who've had breast cancer. Safe and highly accurate, a mammogram is an X-ray photograph of the breast. The technique has been in use for about 30 years.
Still, mammograms aren't perfect. Normal breast tissue can hide a breast cancer, so that it doesn't show up on the mammogram. This is called a false negative. And mammography can identify an abnormality that looks like a cancer, but turns out to be normal. This "false alarm" is called a false positive.
The number of mammogram false positives have caused some debate about when breast cancer screening should start. Besides worrying about being diagnosed with breast cancer, a false positive means more tests and follow-up doctor visits. The process can be extremely stressful and upsetting.
Digital mammography uses the same technique as film mammography, except that the image is recorded directly into a computer. Stereoscopic digital mammography gives a three-dimensional view of breast tissue. But stereoscopic digital mammography is very new and is not widely available yet. The study reviewed here found that stereoscopic digital mammography helps reduce false positives.
Until stereoscopic digital mammography is available to more women, and to make up for mammography's limitations, more than mammography is needed. Women also need to:
Concern about false positives is NOT a good reason to skip mammograms. Work with your doctor to get the best quality mammogram you can:
For more information on mammograms and other tests to detect breast cancer, visit the breastcancer.org Screening and Testing section.
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