Radiation doses for mammography have been overestimated

When asked to assess the amount of radiation a mammography patient will be exposed to, medical physicists may now have a more accurate answer. Modern breast imaging technology shows that radiation dose values used in mammography are lower than originally assumed, according to a study presented at the American Association of Physicists in Medicine (AAPM) Annual Meeting in Anaheim, Calif.

Andrew M. Hernandez, a doctoral candidate at the University of California, Davis, presented the findings. He said newer technologies have changed the way we look at radiation doses related to mammography.

“With the availability of 3D breast imaging techniques, we’re able to basically understand how the glandular tissue and the fat tissue are oriented within the breast,” Hernandez said. “Using this information, we’re able to assess that the arrangement of the glandular and adipose tissue has a really important impact on the resulting radiation dose.”

For the study, Hernandez and colleagues looked at glandular distributions from 219 patients with varying ages, breast sizes and breast densities. Previously, dose values had been estimated using a homogeneous assumption, which means it was assumed that fatty and fibroglandular tissues are uniformly distributed throughout the breast. Thanks to the 3D breast imaging techniques, however, the authors could see the tissues actually have a heterogeneous distribution. So they ran the numbers based on this new information and discovered a significant change in dose values.

“For the small, medium and large-sized phantom, there’s between a 20-40% difference when we assume the more realistic heterogeneous distribution,” Hernandez said. “On average, there’s a 34% decrease in the glandular dose when we have these more realistic depictions of the breast’s anatomy.”

These numbers show that, historically, radiation doses calculated for mammography have been overestimated by approximately 30%. 

Hernandez did note that further research is needed before any changes should be clinically implemented.