The FDA recently announced it will require new safety measures for certain contrast agents used to enhance magnetic resonance imaging (MRI) scans, reports Forbes.

Actor Chuck Norris and his wife Gena have probably been the most public critics of the MRI dyes (they don’t actually change the color of tissue), called gadolinium-based contrast agents (GBCAs). Last month, the couple filed a lawsuit in San Francisco Superior Court alleging that Gena Norris had been poisoned by GBCAs she had received intravenously before three MRI scans over a week in 2012. Contrast agents are sometimes given to patients before MRI scans to provide a clearer image of internal organs, blood vessels and tissue. Gadolinium is a rare earth metal with a number of uses in healthcare.