The news that the American Cancer Society is recommending mammograms starting at age 45 instead of 40 sent shares of Hologic ($HOLX) down more than 5%, though they've since recovered somewhat. Hologic is betting on advanced, 3-D mammography to overcome some of the deficiencies of traditional mammography, such as false positive findings of breast cancer. Hologic accounts for about half of the $2 billion in annual sales for mammography machines, but its share of the 14,000 machines in the U.S. is less 2,000. The devices for 3-D images cost about $400,000, compared to $150,000 to $300,000 for traditional machines. A 2014 study in the Journal of American Medical Association found that 3-D mammography is more effective than the traditional version. But Hologic faces challenges in the segment from new entrants GE and Siemens. Devicemakers are no doubt trying to figure out if the change in guidelines will have a significant effect on the number of mammograms conducted, and whether advanced 3-D images can dispel some of the doubts about the procedure. JAMA said there was not enough data to make a specific recommendation for the advanced modality. Imaging bigwigs GE ($GE), Siemens, and Philips ($PHG) did not respond to a request for comment on the guidelines. More | The new guidelines | The accompanying JAMA editorial