With more than 60 percent of U.S. breast imaging facilities offering digital mammography and more acquiring digital services each month, access to digital mammography is on a solid growth track.
Now with new clinical results showing digital mammography exposes patients to 22 percent less radiation than film mammography, digital is about to hit another growth spurt.
“As digital mammography has now been shown to significantly lower the radiation dose, it is likely that access to it will continue to grow,” said R. Edward Hendrick, Ph.D., lead author of the follow-up study using data from the Digital Mammographic Imaging Screening Trial (DMIST) published in 2005.
The DMIST trial was one of the largest mammography trials in history and marked a turning point for the adoption of digital mammography. The American College of Radiology Imaging Network (ACRIN) enrolled 49,528 women and found that digital mammography detected.
significantly (up to 28 percent) more cancers than film mammography in women younger than 50 years of age, premenopausal and perimenopausal women, and women with dense breasts.
In this latest study, using DMIST data and published in the February 2010 issue of the American Journal of Roentgenology, technical data from 5,102 DMIST participants were evaluated. Researchers found that the dose received by women imaged with digital mammography was significantly lower than that received by the same women imaged with standard film mammography. Researchers found that the average breast radiation dose per view was 2.37 mGy for film mammography and 1.86 mGy for digital, which was 22 percent lower for digital than film mammography.
“The ability to reduce the radiation dose for many women is another step forward for breast cancer screening with mammography — which saves thousands of lives each year,” said Hendrick.
To learn more about the impact of these recent findings, Imaging Technology News (ITN) asked Hendrick if these results would drive the adoption of digital mammography.
ITN: In the latest DMIST trial, you found that overall the radiation dose associated with digital mammography is on average 22 percent lower than that of conventional film mammography. How was the reduced radiation in digital mammography determined?
Hendrick: The follow-up study used the same data from the original DMIST study done a few years ago. It’s taking the technical data from the 10 percent of those women, or 5,102 DMIST participants, as a reasonable sample of the full set of data. We took 150 cases from each of the 33 sites.
It took time to analyze the data, and this was a secondary aim of the DMIST study all along. The data was prospectively collected and analyzed after it was collected.
ITN: You note that the reduction could be greater in women with larger and denser breasts? Why?
Hendrick: It is because of the difference between digital and film detectors. Digital can use a more energetic or harder X-ray beam than film screen because of the way image receptor captures X-rays. That difference is accentuated with thicker breasts. When a breast gets thicker and you are using film screen, you are still constrained to a narrow range of X-rays in order to capture enough with the film screen cassette. With digital detectors, when you go up in breast thickness you can go up in energy quite a bit more. It’s more efficient collecting X-rays at this higher energy.
ITN: Why did you say these results represent another step forward for breast cancer screening with digital mammography?
Hendrick: In addition to doing a better job in terms of accuracy, we are also better able to lower dose.
ITN: In your opinion, will this drive the adoption of digital mammography? If so, why?
Hendrick: They will help a little bit. But I think the adoption of digital mammography is well underway already. More than 60 percent of sites already have it. It will likely be the standard of care in the next several years.
It will be one more encouragement for women to get screened particularly with digital, because it is more accurate and has a lower dose.
Reference: Hendrick, E.; Pisano, E.; et al. Comparison of Acquisition Parameters and Breast Dose in Digital Mammography and Screen-Film Mammography in the American College of Radiology Imaging Network Digital Mammographic Imaging Screening Trial. DOI:10.2214/AJR.08.2114. AJR 2010; 194:362-369.