After a careful review of existing research, the National Institutes of Health (NIH) believe there is enough information regarding gadolinium dissociation in the brain to warrant a review of institutional protocols regarding its use in contrast-enhanced imaging procedures. The opinion was published online Jan. 23 in the Journal of the American College of Radiology.
Gadolinium, a rare-earth metal cytotoxic to humans, is present in nine different contrast agents (GBCAs) currently approved for use by the FDA. Those agents utilize one of two distinct molecular structures—linear or macrocyclic—with varying degrees of stability within the body.
“Macrocyclic-type GBCAs are more stable than linear agents in terms of in vivo dissociation from gadolinium,” wrote lead author Ashkan Malayeri, MD, and his colleagues from NIH. “The highest degree of dissociation has been observed in nonionic linear chelates, followed by ionic linear. The lowest degree of dissociation has been observed with macrocyclic chelating agents.”
Despite alarms from former patients about the dangers of repeated exposure to GBCAs and warnings from respected leaders within the radiology community, there is no confirmed evidence of negative patient consequences stemming from dissociation or gadolinium retention in the brain.
However, recent developments merit a review of best practices and protocols for deciding when and how to utilize GBCAs, according to NIH, who issued the following recommendations after a thorough analysis of existing research.
- GBCAs should be used only when clinically indicated or when specified in an institutional review board-approved protocol.
- When GBCAs are required, consider the use of a macrocyclic GBCA (eg, gadobutrol, gadoteridol, gadoterate meglumine) rather than a linear agent.
- For patients with documented sensitivity (e.g., hives) to macrocyclic agents, it is appropriate to use linear agents when clinically indicated.
- MRI protocols should always consider FDA label indications and dosing schemes for administration of GBCAs.
- Encourage intra- and interdepartmental research programs to evaluate T1 shortening in the brain and other organs in patients who have received multiple doses of GBCAs.
While more research is needed into GBCAs and the long-term effects of gadolinium retention in patients, balancing the continued use of this valuable imaging resource with a cautious eye toward patient safety is the best path forward, according to NIH.
“GBCAs are indispensable adjuncts to MRI, with numerous studies showing their efficacy in improving the accuracy of MRI studies,” wrote Malayeri et al. “Although it is not yet known if there is a clinical implication of brain deposition of gadolinium, concerns for patient safety are of paramount importance, and thus internal review of institutional policies on GBCA use are warranted.”