The FDA is mandating a new class warning and labeling changes for all gadolinium-based contrast agents — as well as requiring manufacturers to conduct additional human and animal safety studies.

The agency listed concerns of gadolinium — a rare earth metal used during MRIs — remaining in patients’ bodies, including the brain, for months to years after injection.

However, the FDA said it concluded the benefits of all approved agents continue to outweigh any potential risks, and that gadolinium retention has not been directly linked to adverse effects in healthy patients.

The FDA is urging healthcare professionals to consider the retention characteristics of each agent when choosing a particular product, especially in patients requiring multiple lifetime doses, pregnant women, children and patients with inflammatory conditions, but advised them to not avoid or defer necessary scans.