Gadolinium is a rare earth metal with atomic number 64. It has a silvery-white appearance and is relatively stable in air compared to other rare earth metals. It has several important uses in industry, including the production of computer memory, nuclear reactor control rods, and phosphors for color television tubes.

One of the most important applications of gadolinium is in magnetic resonance imaging (MRI) technology. Gadolinium compounds are frequently used as contrast agents to enhance the magnetic resonance signal in medical imaging procedures. This makes it easier for doctors to detect and diagnose medical conditions such as tumors, infections, and cardiovascular disease. Recent research has suggested that some gadolinium-based contrast agents may cause adverse health effects in patients with reduced kidney function, so new contrast agents are being developed that are less likely to cause these side effects.