Contrast agents are often used in diagnostic technologies like MRIs. There are many different types of contrast agents, which can make tissues much easier to see against the background fluids of the body. These agents can include iodine-based agents or gold nanoparticle agents in CT scans, or gadolinium chemicals in magnetic resonance imaging (MRI). The use of these agents is widespread, and as they become more common, so have concerns about their safety.
The US Food and Drug Admiinistration (FDA) warned in 2018 that gadolinium-based contrast agents can hang around in the body, though at that time, they noted that the impacts of this retention were unclear.
Now, scientists who study gadolinium health risks have determined that oxalic acid, which is found in many foods, can produce gadolinium nanoparticles in human tissues. The findings have been reported in the journal Magnetic Resonance Imaging.
Gadolinium is often attached very tightly to other molecules and the body can excrete the substances without harm. But studies have also identified gadolinium particles in the kidney and the brain. They have also been detected in blood and urine years after a person was initially exposed.
Unresolved questions include why gadolinium becomes unbound from its attachment to other molecules, and why some people have an adverse reaction while others don't.
The most serious disease that MRI contrast agents might cause is nephrogenic systemic fibrosis, noted Brent Wagner, MD, professor at University of New Mexico. About 50% of patients have gotten this disorder after only one exposure, said Wagner. This disorder can cause the skin, heart, and lung tissue to thicken and harden, and painful joint problems.
In this study, the researchers focused on a molecule called oxalic acid since it binds to metal ions (and was suspected to bind to gadolinium). Oxalic acid is also found in many foods, like nuts, berries, chocolate, spinach, and rhubarb. It may also be generated by the intake of foods or supplements that contain vitamin C. When oxalate attaches to kidney stones, kidney stones form.
The research suggested that oxalic acid can cause tiny bits of gadolinium to precipitate from contrast agents and go on to form nanoparticles. These can then penetrate various tissues. But this process may also not happen in every patient.
Wagner suggested that people carrying high levels of oxalic acid may be more likely to be affected.
"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."
Now the researchers want to learn who is impacted by this phenomenon so that these problems can be avoided.
Sources: University of New Mexico, Magnetic Resonance Imaging
