Contrast media (also known as contrast media) is one of the most commonly used drugs in diagnostic radiology, and is used for CT enhancement, interventional angiography, and excretory urography and other lumpectomy examinations. Contrast media are divided into negative contrast media and positive contrast media according to their molecular weight and the dose of absorbed X-rays. Negative contrast agents are mainly gases, such as air, oxygen and carbon dioxide. Positive contrast agents are mainly barium and iodine-containing contrast agents. Barium is barium sulfate, which is used for gastrointestinal contrast examination. There are many kinds of iodine-containing contrast agents. They are mainly used for CT enhancement, interventional contrast, urography and other lumen contrast examinations, all of which are organic iodine agents. The development and improvement of iodine-containing contrast agents have two main purposes: firstly, to increase the iodine content in order to obtain the best contrast, and secondly, to reduce toxicity and side effects so that patients can tolerate them. Early studies with these objectives focused on increasing iodine content, from the latest single iodine proton heterocycles to double iodine proton heterocycles to benzene ring derivatives containing three iodine protons. The products dissociate into anions and cations in solution and are called ionic contrast agents. It is stable in nature and has good contrast but the solution is hypertonic and patients often suffer from toxic side effects. Therefore, the non-ionic contrast agents that appeared after the 70s have reduced permeability and are even close to plasma, with small toxic side effects, high biosafety and low toxicity to the nervous system. (1) Ionic contrast agents refer to pantothenate and isopantothenate. Pantothenate has sodium pantothenate and pantothenic glucosamine. Sodium ion has damage to vascular endothelium and pain at intravenous injection. Glucosamine does not have this side effect. Pantethine may cause ventricular fibrillation and has a high viscosity, so the two are mixed to form a compound pantethine. We use 76% compounded pantopamine for cardiovascular imaging, urography, and direct introduction of bile ducts, uterine tubes, and fistulas. In some cases for oral gastrointestinal imaging or CT abdominal examinations for intestinal oral contrast. Isopantothenic acid is a tautomer of pantothenic acid, with isopantothenic sodium and isopantothenic glucosamine. The scope of application is approximately the same as that of pantothenate. (2) Non-ionic contrast agent In the 70’s, Naicomin first synthesized methylpantopamine (Amipak), which was generally welcomed because it dissolved in water without ionization, and its osmotic pressure, neurotoxicity and viscosity were reduced, but its storage and use were inconvenient and was later replaced by the development of new products. The products developed after the 80’s are iodophoresol (Onepak), iodopeptidol (Iopiol, Iopapol), iopromide (Uvirixin), iovisol (Anjali, Ioflurol), which are all non-iodine ionic monomer organic contrast agents. Compared with ionic contrast agents, they have the following advantages: they are not salts, no ionization in aqueous solution, and low osmotic pressure, which significantly reduces patients’ headache, burning sensation and discomfort caused by vasodilation in clinical application. The absence of carboxyl groups greatly reduces neurotoxicity, and the toxicity of intravenous administration is significantly reduced.ƒ The introduction of 4-6 alcohol groups in the molecular structure increases hydrophilicity, improves water concentration, and reduces viscosity. Contrast agent toxicity reactions are further reduced, and it is suitable for cardiovascular imaging and CT enhancement scans. We have three non-ionic dimeric organic iodine contrast agents, iodophorol, iopapol and iofluorol, whose molecular structure contains 8~12 alcohol groups and 2 triiodophenyl rings, and whose osmotic pressure is close to the plasma osmotic pressure, making them suitable for crestal medulla and brain pool imaging. There are iodotriptan (Isohexan) and iodidiol (Vistapac), which are not available in our hospital. 2, ionic and non-ionic contrast agent toxic side effects and biological safety comparison According to the statistical analysis of a large group of cases at home and abroad. The incidence of toxic side effects of intravenous injection of non-ionic contrast agent is 76.3% less than that of ionized type. The occurrence of reactions was mainly mild and moderate, and the reduction in the incidence of severe reactions was more obvious. The mortality rate of ionic contrast injection was 1:3000, while that of nonionic contrast was only 1:250,000, and the LD50 of mice tested intravenously showed that nonionic contrast was about 3 times higher than ionic contrast. Now, non-ionic contrast agents have low incidence of toxic side effects and high biosafety, so the use of non-ionic contrast agents is advocated.