When an enhanced MRI is done, a needle called a contrast agent is injected through the patient’s vein. The most commonly used MRI contrast agent in clinical practice is gadopentetate monoglucosamine, which is an ionic, non-specific extracellular fluid contrast agent. It is currently a very safe contrast agent, with a very low incidence of side effects, and the majority of people have no problems with the allergy test that the physician performs on the patient before the test is done. By injecting contrast agent can help improve the signal-to-noise ratio and contrast-to-noise ratio of the image, which is beneficial to the detection of lesions, and can also help characterize lesions by different enhancement methods and types of lesions, so it is now more and more widely used in clinical applications.