A new study has found why MRI scans may leave harmful metals behind in a person’s body.

The University of New Mexico (UNM) study explored health risks caused by toxic rare earth metal gadolinium, which is used in MRI imaging.

Gadolinium-based contrast agents, which create sharper images of the scan, are injected into the body before an MRI to explore any potential issues in the body.

And while the metal is usually excreted from the body, and most people experience no adverse side effects, previous research has shown some gadolinium particles have been left behind. These particles have been found in the brain, kidney, and even in the blood and urine years after an MRI.

According to the US Food and Drug Administration (FDA) the main adverse health effect related to gadolinium retention is a condition called nephrogenic systemic fibrosis (NSF), found in patients with pre-existing kidney failure.

NSF can cause a thickening and hardening of the skin, heart and lungs—and cause painful contracting of the joints.

The FDA has logged reports of adverse events involving multiple organ systems in patients who had had normal kidney function, but a causal association between these events and gadolinium retention could not be established.

Now the new study, led by UNM professor Brent Wagner, MD, has found a connection between gadolinium and oxalic acid, a molecule found in foods which binds with metal ions, leading to medical issues such as kidney stones.

The research team used test tube experiments and found that oxalic acid caused tiny amount of gadolinium to precipitate from the contrast agent and form nanoparticles, which infiltrated cells of different organs.

Oxalic acid also forms in the body when people eat foods or take supplements containing vitamin C, and Wagner said in a statement that he “wouldn’t take vitamin C if I needed to have an MRI with contrast because of the reactivity of the metal.”

He said a person’s “metabolic milieu” may determine whether a patient forms the nanoparticles.

“It might be if they were in a high oxalic state or a state where molecules are more prone to linking to the gadolinium, leading to the formation of the nanoparticles,” he said. “That might be why some individuals have such awful symptoms and this massive disease response, whereas other people are fine.”

In their study, it was found that almost 50 percent of the patients with gadolinium traces in the body had only been exposed to the contrast agent one time, meaning there was “something that is amplifying the disease signal.”

The nanoparticle formation “might explain why there’s such an amplification of the disease. When a cell is trying to deal with this alien metallic nanoparticle within it, it’s going to send out signals that tell the body to respond to it.”

Wagner’s team is currently researching ways to identify who may be at the biggest risk from gadolinium contrast agents, by building an international patient registry including blood, urine, fingernail hair samples to gather evidence of gadolinium accumulation in the body.

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Reference

Henderson, I. M., Benevidez, A. D., Mowry, C. D., Watt, J., Bachand, G. D., Kirk, M. L., Dokładny, K., DeAguero, J., Escobar, G. P., & Wagner, B. (2025). Precipitation of gadolinium from magnetic resonance imaging contrast agents may be the Brass tacks of toxicity. Magnetic Resonance Imaging, 119. https://doi.org/10.1016/j.mri.2025.110383