Magnetic resonance imaging (MRI) enhancement examination requires intravenous injection of contrast agent (commonly known as contrast), which can improve the sensitivity and specificity of MRI examination, help to detect lesions that are not detected by plain scan, help to determine the boundaries of lesions, and help to differentiate benign and malignant lesions. Current studies have shown that enhanced MRI examination has good safety and tolerability, but there is still a chance of local reactions and systemic toxic side effects, and even death, so it is necessary to pay attention to the following points: 1. For severe renal insufficiency and subjects with glomerular filtration rate less than 30 ml/min, the use of contrast agent is not recommended, because the use of contrast agent in renal insufficiency can lead to delayed discharge of contrast agent and increase The chance of contrast agent dissociation in vivo may cause adverse consequences, such as nephrogenic systemic sclerosis. 2. Patients with allergic tendency need to be cautious in using contrast agents because their chances of allergic reactions are higher than those of other patients. Allergic patients may experience nausea, vomiting and skin mucosal allergic reactions after contrast agent injection; transient warmth or pain may occur at the injection site during the injection process, which is due to the hypertonicity of contrast agent, so penetration into the paravalvular tissue may cause pain and swelling. In a few cases, systemic allergic-like reactions or even shock can occur, and in more serious cases, even death. 3. Before the injection of contrast agent, it is generally required to fast for 2 hours. Allergic reactions mostly appear within 20 minutes after drug injection, so patients should leave half an hour after the examination is completed for observation. Patients should go to the hospital quickly for consultation and treatment if discomfort occurs after discharge. 4.We should try to drink water within 24 hours after the examination according to the body condition to accelerate the excretion of contrast agent. 5.Clinicians can also be consulted to adopt the route of intravenous infusion according to the heart function and kidney function.