Urgent warnings by government experts about the risks of routinely using powerful CT scans to screen patients for colon cancer were brushed aside by the Food and Drug Administration, according to agency documents and interviews with agency scientists. Such scans can deliver the radiation equivalent of 400 chest X-rays. An estimated 70 million CT scans are performed in the United States every year, up from three million in the early 1980s. As many as 14,000 people may die every year of radiation-induced cancers as a result, researchers estimate. The use of CT scans to screen healthy patients for cancer is particularly controversial. The internal dispute [at the FDA] has grown so heated that a group of agency scientists who are concerned about the risks of CT scans say they will testify ... that F.D.A. managers ignored or suppressed their concerns, and that the resulting delay in making these concerns public may have led hundreds of patients to be endangered needlessly. Scores of internal agency documents made available to The New York Times show that agency managers sought to approve an application by General Electric to allow the use of CT scans for colon cancer screenings over the repeated objections of agency scientists, who wanted the application rejected.