CT scans, X-rays and other imaging methods save lives, but they also expose patients to high cumulative levels of radiation. In a study published in the New England Journal of Medicine, researchers surveyed more than 950,000 U.S. adults in the 18-to-64 age group for two years. In that period, nearly 70% of the subjects underwent at least one imaging procedure that involved radiation. Moderate levels of radiation were experienced by 194 subjects per 1,000 per year, while 19 per 1,000 got high doses. The study raises anew concerns about how to balance the good the tests can do with the concern that the radiation exposure increases lifetime cancer risk. Canada is taking steps to correct the problem: the government is partnering with the private health care industry to establish a national radiation-dosage registry in which records of patients' radiation exposure would be stored. This could then become part of their permanent medical record, allowing doctors to consider whether a nonradiative scan like ultrasound would be a better choice. The U.S. could initiate a similar system — one that would become all the more effective as the country switches from paper to electronic medical records.