The Food and Drug Administration announced today it is investigating the risk of brain deposits for patients who are given repeated MRIs using imaging drugs that contain a heavy metal.

The FDA did not announce any label changes for the nine medicines that contain the metal, gadolinium, saying there was a “need for additional information.” However, “to reduce the potential for gadolinium accumulation,” the safety announcement asked health care professionals to “consider limiting” their use and to reexamine “the necessity of repetitive” MRIs involving these drugs.

ProPublica has extensively reported on the potential risks of contrast agents, including a call by two prominent radiologists for more research following recent studies that unexpectedly found gadolinium in the brain tissues of patients. The patients each underwent at least four scans using two of the nine agents currently on the market. It is not known if the deposits are harmful.

Gadolinium-based contrast agents have been on the market for a few decades and enhance the scanned images. About one-third of the 20 million MRIs in the United States each year use one of the nine agents. The FDA’s call to doctors to limit use of the agents seeks to make sure the “additional information provided by the contrast is necessary.”

Normally, the gadolinium is largely eliminated from the body via the kidneys following the drug’s injection. As such, patients are screened to ensure they do not have kidney disease. But the recent studies found that gadolinium can remain in the brain even in patients whose kidneys function normally.

In the past, the FDA has been slow to move in this area.

In 2007, it ignored the advice of two of its medical reviewers who wanted to ban one of the drugs, Omniscan, made by GE Healthcare, for patients with severe kidney disease. In 2010 the agency reversed course and recommended that Omniscan and two other drugs shouldn’t be used in patients with impaired kidneys. The other drugs were Magnevist, made by Bayer HealthCare, and Optimark, sold by Mallinckrodt Pharmaceuticals.

The gadolinium brain deposits discovered in the new research involved patients who had been administered Magnevist and Omnsican, leading some experts to suggest doctors should think twice about which of the nine agents to prescribe.

GE Healthcare and Bayer say their primary concern is patient safety and that they have been examining the issue in light of the new research. The FDA said its toxicology research center “will study the possible safety risk further” in conjunction with industry and outside scientists.

Sarah Peddicord, an FDA spokeswoman, declined to say when the research would be completed but said the agency would “update the public when more information is available.” She added that manufacturers have been asked to report any problems with gadolinium retention and that “some manufacturers have already initiated animal and clinical studies” to further investigate the issue.