When doctors counted the number of medical scans patients underwent in the emergency room at Brigham and Women's Hospital, some patients clearly stood out. One 45-year-old woman with a history of kidney stones had 70 CT scans over 22 years. The cumulative radiation exposure from those scans, the researchers estimated, raised her lifetime risk of cancer by about 10%. Partly because of these results—overall 5% of patients studied underwent at least 22 scans in the 22-year study period—the hospital plans to become one of the first in the United States to notify doctors of their patients' imaging histories, and resulting cancer risk.