Gd-DTPA is a very safe contrast agent, its LD50 is about 20mmol/kg body weight, its conventional dose is 0. 1mmol/kg body weight, and its safety factor (LD50/effective dose) is as high as 200 (the safety factor of iodine contrast agent is 8~ 10). The incidence of side effects of Gd-DTPA is very low, which is reported as 1.5% ~ 2.5%. Most of them are dizziness, transient headache, nausea and vomiting, rash and so on. The incidence of serious adverse reactions is extremely low, about one million to two million, which can be manifested as dyspnea, decreased blood pressure, bronchial asthma and pulmonary edema, and in severe cases, it can lead to death. Most patients with severe reactions have a history of respiratory diseases or allergies. The mechanism of side effects of gadolinium gluconate is not clear. At present, most authors believe that it is mainly related to the chemical toxicity of gadolinium itself. The high risk factors and prevention of side effects of Gd-DTPA are similar to those of water-soluble iodine-containing contrast agents. Some manufacturers have successively developed nonionic extracellular fluid MR contrast agents, such as Gd-DO3A-butrol of Schering Company, Gd-DTPA-BMA of Nike Ming Company, Gd-HP-DO3A of Blach Company, etc. These nonionic contrast agents have low permeability and further improve their safety. Among them, Ou Naiying has been sold in the domestic market.