Techniques Assessed for Measuring Breast Density

Two new studies have evaluated three different methods for effectively measuring breast density--the relative portion of tissue to fat in a woman's breasts and a strong indicator of breast cancer risk.

Both studies were conducted by a group of medical physicists from the University of California, Irvine (USA), led by Dr. Sabee Molloi, and were presented at the 52nd annual meeting of the American Association of Physicists in Medicine (AAPM) in Philadelphia, PA (USA). The first study compared two existing techniques for measuring breast density--cone-beam computed tomography (CT) and breast magnetic resonance imaging (MRI). The research revealed that both techniques gave highly similar estimates of the density of 20 pairs of breasts scanned post-mortem. The second study showed the promise of a third technique called dual-energy mammography for measuring breast density.

"A better measure of breast density should yield a more accurate assessment of risk for developing breast cancer,” said medical physicist Dr. Justin Ducote, who presented the study on dual-energy mammography on July 19, 2010.

Doctors have known since the 1970s that women who have dense breasts are at greater risk for developing breast cancer. Moreover, tumors may be hard to detect when imaging dense breast, since they have a greater portion of glandular tissue relative to the amount of fatty tissue, and the glandular tissue can obscure the tumors.

Measuring breast density is made difficult by the fact there is no currently accepted gold-standard method for doing so, according to Dr. Ducote. In Dr. Ducote's study, the research applied dual-energy mammography to 20 pairs of postmortem breasts. The technique makes use of dual energy X-ray imaging, where overlapping tissue signals can be isolated and quantified by exploiting the change in X-ray attenuation at different energies. According to Dr. Ducote, this allowed breast density to be measured from digital mammograms.

Dr. Ducote's colleague Dr. Huy Le presented related research at the meeting. In Dr. Le's study, the group analyzed the ability of cone-beam CT and breast MRI to measure breast density in the same 20 pairs of postmortem breasts. They discovered that breast density measurements using these two techniques were highly correlated. "If we can get agreement of breast density measured on multiple imaging modalities, our confidence in the accuracy of the value we obtain will increase,” concluded Dr. Le.

The next step, according to the researchers, is to quantify the exact density of the breasts in the study through chemical composition analysis--a destructive technique, which is why the research was conducted using postmortem tissue.

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