An MRI contrast agent is a substance used during an MRI (Magnetic Resonance Imaging) scan to enhance the visibility of internal structures. These agents help differentiate between normal and abnormal tissues, making it easier for doctors to diagnose conditions such as tumors or inflammation. The most common type of contrast agent contains gadolinium, a rare earth metal that alters the magnetic properties of nearby water molecules in the body. When injected into a patient's bloodstream, the contrast agent improves the clarity of the images produced by the MRI machine. This allows for more accurate assessments of organs, blood vessels, and other tissues. While generally safe, some patients may experience allergic reactions or side effects, so medical professionals assess risks before use.