Digital mammography interpretation takes longer than film reading

Researchers at the University of Texas M.D. Anderson Cancer Center in Houston have confirmed what mammographers have long suspected: Digital screening mammograms may take twice as long to read than film. Understanding all variables could boost or make up for interpretation speed.

According to the FDA's Center for Devices and Radiological Health, about a third of all breast imaging facilities in the U.S. have incorporated digital mammography system into their practices in the last decade. The clinical literature has established a number of advantages for digital mammography compared with film, such as acquisition time and storage costs savings and a small but significant boost in diagnostic accuracy. But the same data also suggest that digital studies take longer to read.

An investigative team led by Dr. Tamara Miner Haygood looked into this issue by assessing the time that four radiologists needed to interpret 268 digital screening mammograms and 189 screen-film mammograms. The investigators compared interpretation times for several different variables. They found that it took all readers an average of four minutes to interpret digital screening mammograms and slightly more than two minutes to read film studies. They published their findings in the January issue of the American Journal of Roentgenology (2009;192:216-220).

No previous studies have deeply investigated the multiple variables that affect interpretation times. Haygood and colleagues, however, identified factors that might have contributed to time differences. These variables accounted for BI-RADS code, number of images obtained, presence or absence of abnormalities, and availability of older studies for comparison. The investigators also observed individual radiologists' interpreting habits or techniques that may have affected interpretation time, such as whether the radiologist looked for and hung up additional films.

Previous studies have suggested that conversion of comparison studies from film to digital may speed interpretation times. The investigators also found, however, that digital mammogram interpretation times remained significantly longer than film even when they were matched with digital comparison studies.

Radiologists should be able to make a more informed choice about whether digital or screen-film mammograms are right for their practice. If they choose digital screening mammograms, they will have a better idea of how much time to allow for reading them, Haygood said.

"It will be very beneficial if manufacturers of digital equipment, in cooperation with radiologists, can improve equipment and reading techniques to bring interpretation speed for digital mammograms closer to interpretation speed for screen-film mammograms," she said.

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