Gadolinium is the chemical element with symbol Gd and atomic number 64. It is a special heavy metal with a structure making it strongly paramagnetic. Paramagnetism is an intrinsic property of certain materials which causes the element to become temporarily magnetized when placed in an external magnetic field (an MRI). It is this unique property that makes gadolinium an ideal contrast agent for MR imaging.
Free gadolinium is toxic to humans. Gadolinium that is injected into your body for MR imaging is bound to another chemical, called a ligand. The binding of the gadolinium metal with the ligand is called a chelate. MRI chelates come in two flavors, macrocyclic and linear. The linear chelate binds Gd to the end and wraps around the heavy metal forming a shell. Linear agents also come in two flavors, non- ionic (Omniscan and Optimark) and ionic agents (MultiHance, Magnevist, and Eovist). The ionic agents are generally considered safer for patients than non-ionic agents. Macrocyclic ligands (Dotarem, Gadavist, ProHance) form a 3D cage around gadolinium encasing the metal.
A little more than a year ago Europe banned the use of linear agents. The FDA and US radiology community was in opposition to this decision. It is felt that each chelate has its own safety profile with linear ionic agents offering benefits not available with macrocyclics. For example, contrast agents are largely eliminated from the body by being filtered through your kidneys but Eovist has a significant amount processed by the liver making it valuable in the evaluation of liver lesions over other agents. MultiHance has properties that allow it to provide superior contrast to other agents, often requiring only half as much volume as the other contrast agents.
So why the scare? Gadolinium has been used in more than 100 million patients worldwide over the past 25 years. Gadolinium toxicity was first discovered in patients with severe chronic renal disease. In this extremely small subset of patients, gadolinium was discovered to cause nephrogenic systemic fibrosis (NSF). Nephro means kidney, systemic is everywhere, and fibrosis is scarring. The name illustrates the disease stemming from the kidney failure and causing your whole body to scar up eventually resulting in multiorgan failure and death. Okay, that sounds bad. Since the discovery of NSF, strict national guidelines have been implemented and the disease virtually eliminated. Blood tests are performed on patient’s depending upon certain demographics with increased risk for kidney damage (e.g. age, diabetic, hypertensive, known kidney disease). If the kidneys are severely impaired, then it is considered an absolute contraindication for intravenous contrast administration.
Recently, it has been discovered that Gd deposits in the brain. In fact, Gd deposits everywhere in the body, but builds up in higher concentrations in the kidneys and brain. That being said, as was mentioned earlier, over 100 million patients worldwide have received gadolinium, including yours truly. Other than NSF, gadolinium deposition in the tissues has not been shown to cause any other harm to date. Specifically, gadolinium deposition in the brain has not been shown to correlate with any neurologic symptoms, much less be the cause of any neurologic impairment.
Finally, you ask, “Do I need gadolinium for my MRI?” Well that depends on why your exam was ordered. In general, contrast is beneficial in the evaluation of patients with diagnoses or suspected conditions involving cancer, infection, and inflammation (think autoimmune diseases like Multiple Sclerosis and Crohn’s disease). Contrast agents are also helpful in the evaluation of postoperative patients and the identification of potential complications. Are there risk to receiving gadolinium? Well of course, but in a large majority of the circumstances, the benefits greatly outweigh the risks. If you have an MRI ordered and it is with contrast, what can you do to maximize your benefit to risk ratio? For one, if you are a patient being evaluated for postoperative complication, infection, inflammation, or cancer, then the answer is almost certain that you would benefit from a contrast agent. But if you are a patient without those concerns, then you might not need Gadolinium. As a radiologist, I speak to concerned patients almost daily discussing their individual case with them and evaluating their own risk-benefit profile. I have reviewed many cases with the patient still on the scanner to determine whether or not I see any obvious finding that should be further characterized with a contrast agent. In fact, this is routinely performed in our practice with patients having compromised kidney function and the pediatric patient population. I would suspect half of the cases I review with the patient on the scanner do not end up receiving contrast.
Well I hoped this provided some basic introductory information about Gadolinium and “gadolinium deposition disease.” Contrast agents are medicine regulated by the FDA. Just like any medication you are prescribed, there are potential risks and benefits. Many referring healthcare providers do not know when it is appropriate to utilize a contrast agent and that is okay. I do not always know what antibiotics to give or what surgical instrument is optimal for each case and that is normal. The study of medicine is highly complex, which is why we have so many specialists. I am a radiologist. I specialize in imaging studies, some of which use gadolinium contrast agents. It is my duty and responsibility to aid healthcare providers and patient’s in obtaining the most reasonable exam to try and answer the clinical question. I am here for you.
I hope you enjoyed this blog. I’ve attempted to jump on the bandwagon regarding medias current interest in gadolinium toxicity to ride the wave of popularity but also to dispel any myths and hopefully provide some comfort and anxiety relief. Let me know what you thought! Sound off in the comments.