Nanoparticles of toxic metal in MRI scans can infiltrate human tissues: Study

Researchers from the University of New Mexico in the US, while studying the health risks posed by gadolinium, a toxic rare earth metal used in MRI scans, have found that oxalic acid, a molecule found in many foods, can generate nanoparticles of the metal in human tissues.

In a new paper published in the journal Magnetic Resonance Imaging, the team led by Brent Wagner, professor in the Department of Internal Medicine, sought to explain the formation of the nanoparticles, which have been associated with serious health problems in the kidneys and other organs.

"The worst disease caused by MRI contrast agents is nephrogenic systemic fibrosis," he said. "People have succumbed after just a single dose."

The condition can cause a thickening and hardening of the skin, heart and lungs and cause painful contracture of the joints.

Gadolinium-based contrast agents are injected prior to MRI scans to help create sharper images, Wagner said.

The metal is usually tightly bound to other molecules and is excreted from the body, and most people experience no adverse effects.

However, previous research has shown that even in those with no symptoms, gadolinium particles have been found in the kidney and the brain and can be detected in the blood and urine years after exposure.

Scientists are left with intertwined puzzles: Why do some people get sick, when most don't, and how do gadolinium particles become pried loose from the other molecules in the contrast agent?

"Almost half of the patients had been exposed only a single time, which means that there's something that is amplifying the disease signal," Wagner said.

Wagner's team focused on oxalic acid, which is found in many plant-based foods, including spinach, rhubarb, most nuts and berries and chocolate, because it binds with metal ions.

The process helps lead to the formation of kidney stones, which result when oxalate binds with calcium. Meanwhile, oxalic acid also forms in the body when people eat foods or supplements containing vitamin C.

In test tube experiments, the researchers found that oxalic acid caused minute amounts of gadolinium to precipitate out of the contrast agent and form nanoparticles, which then infiltrated the cells of various organs.

The finding points to a possible way to mitigate some of the risks associated with MRI scan.

"I wouldn't take vitamin C if I needed to have an MRI with contrast because of the reactivity of the metal," Wagner said. "I'm hoping that we're getting closer to some recommendations for helping these individuals."