It is a phone call that women dread. Something is not quite right on the mammogram: come back for another one. But don’t worry, the script goes, most repeat tests wind up normal. Still, most women know someone who has breast cancer, and even the calmest, most rational minds may think the worst when summoned back to the clinic. At many centers, these nerve-racking calls are on the rise, at least temporarily — 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...