WASHINGTON (March 30, 2010)--Former Food and Drug Administration scientist Dr. Julian Nichols says he was fired after he raised concerns about the risks of radiation exposure from high-grade medical scanning.

Nicholas told an audience of imaging specialists that he and other FDA staffers "were pressured to change their scientific opinion," by managers.

Nicholas made his remarks at a public meeting designed to kick off the FDA's campaign to reduce radiation exposure from medical scanning.

The agency is seeking input from physicians and manufacturers on additional safety controls and training to improve CT scanners and other medical imaging devices.

The amount of radiation to which an average American's is exposed has nearly doubled in the last three decades, largely because of imaging tests, according to the FDA.