cross-sections, like turning pages of a booshgs identifying tumors like this one that could have been missed. the study find they increase early detection by 29%, decrease the number of stressful false-positives and fewer women have to go back for repeat screenings. how significant is a development like this when it comes to diagnosing breast cancer? >> anything we can do to pick up cancers that are smaller and at an earlier stage is a huge improvement. >> reporter: these machines do omit more radiation than traditional mammograms since they're more expensive, they're relatively rare. doctors we spoke to hoping that will change. many seeing this as the wave of the future. mara schiavocampo, abc news, new york. and a sober announcement from former "good morning america" co-host joan lunden revealing the world that she has breast cancer. >> lunden told "gma's" robin roberts, the aggressive form of cancer was detected by a ultrasound. the 63-year-old mother of seven