The FDA is warning that gadolinium-enhancing contrast agents used in MRI imaging .
Although there are no known health risks at the time, the agency is investigating whether these brain deposits could become problematic.
The investigation follows recent reports that deposits of gadolinium-based contrast agents remain in the brains of some patients who have four or more contrast MRI scans, long after their last dose.
The FDA said physicians should consider limiting the use of these agents to "clinical circumstances in which the additional information provided by the contrast is necessary," also urging them to reassess the necessity of repetitive contrast MRIs in established treatment protocols.
The warning doesn't affect contrast-enhancing agents, such as those that use iodine or other radioisotopes.
The FDA will investigate the risk in conjunction with the National Center for Toxicological Research, and it's not requiring any label changes for gadolinium-enhancing contrast agents at this time.