By DENISE GRADY

It is a phone call that women dread. Something is not quite right on the mammogram: come back for another one.
At many centers, these nerve-racking calls are on the rise - the price of progress as more and more radiologists switch from traditional X-ray film to digital mammograms, in which the X-ray images are displayed on a computer monitor.
Problems can arise during the transition period, while doctors learn to interpret digital mammograms and compare them to patients’ previous X-ray films.
Comparing past and present to look for changes is an essential part of reading mammograms. But the digital and film versions can sometimes be hard to reconcile, and radiologists who are retraining their eyes and minds may be more likely to play it safe by requesting additional Xrays - and sometimes ultrasound exams and even biopsies - in women who turn out not to have breast cancer.
The rush to digital is occurring in part because for certain women - younger ones and others with dense breast tissue - it is better than film at finding tumors. Digital is especially good at picking up tiny calcium deposits, or calcifications, which are sometimes - but by no means always - a sign of cancer.
In the long run, radiologists say, digital technology will make mammograms more accurate for many women.
There have been no studies yet to measure what happens during the transition period, but many radiologists say they do find themselves calling more women back.
Dr. Mary Mahoney, a professor of radiology and the director of breast imaging at the University of Cincinnati Medical Center, said, “I am living through the pain of this transition period on a daily basis.”
Dr. Mahoney’s center recently opened an entirely digital clinic for breast cancer screening. Regarding the higher callback rates, Dr. Mahoney said: “I know it’s not a small thing, the anxiety. Patients are practically in tears because they’re so worried. But I think in the long run it’s going to be to everybody’s benefit.”
Dr. Margarita Zuley, the director of breast imaging at Magee-Women’s Hospital at the University of Pittsburgh Medical Center, said it could take six months to a year to learn to interpret the images.
Lecturing in New York recently , Dr. Zuley told an audience of radiologists: “When you first start out, you may feel a little anxious and recall more patients because everything looks like a cancer to you. It’s O.K. Just bring the patients back. It’s part of the learning curve.” Meanwhile, patients or their insurers are paying for the extra tests.
Radiologists say digital technology lets them adjust features like contrast and magnification, and see things that were blurry or maybe even invisible on film. In the long run, doctors say, the increased clarity of digital mammograms may lead to fewer callbacks of healthy women - but it still takes time to learn how to use them properly.