Non ionic contrast medium is the second generation of CT contrast medium. For advantages of non ionic contrast media, compared with the first generation of ionic contrast medium, the non ionic contrast medium has greater water solubility. In addition, it does not ionize in water, which has the advantages of low viscosity and low osmotic pressure. Clinically, the incidence and severity of toxic side effects of the non-ionic contrast medium are significantly lower than that of the ionic contrast medium.
(1) Iohexol: It is a water-soluble non ionic X-ray contrast medium developed in the 1980s. It has the advantages of high water solubility, low viscosity, low osmotic pressure, and low toxicity. It is clinically used in cerebral angiography, coronary angiography, etc.
Iohexol injection has an excellent molecular structure, which can greatly improve user safety and significantly reduce adverse reactions. The iodinated contrast medium has excellent clinical feedback and good imaging effects. In 1998, Beilu's iohexol injection was launched.
(2) Iodophor: It has a better chemical structure than that of the nonionic iodinated contrast, it is considered to be the most hydrophilic non ionic contrast medium and it has a wide range of clinical applications.
(3) Iopamidol: Iopamidol has high iodine content and a good imaging effect. It has low toxicity to blood vessel walls and nerve tissues, and is stable in nature. It is suitable for various types of angiography, enhanced CT scans, urography, myelography, cisternography, etc.
(4) Iopromide: It can be used for enhanced CT examination, digital subtraction angiography (DSA), arteriography, venography, intravenous urography and body cavity angiographies such as arthrography, gastrointestinal angiography and hysterosalpingography.
(5) Iodixanol: Iodixanol visipaque is a new type of isotonic dimer contrast medium. According to the visipaque package insert, iodixanol is a non ionic dimer that contains hexaiodine. It has a common name of iodixanol injection, the trade name of Visipaque.
(6) Iomeprol: Iomeprol has low osmotic pressure, good tolerability, stable performance, and a good imaging effect. It has been widely used and the trade name is Iomeprol.
Compared with the ionic contrast medium, the advantages of non ionic contrast agents are as follows:
(1) Osmotic pressure: The non ionic contrast medium replaces the carboxyl group attached to the benzene ring in the ionic contrast medium with an amide group. The change in the chemical structure prevents ionization in the solution.
(2) Charge: The non ionic contrast medium does not have the carboxyl group in the molecular structure, and it does not generate charged ions in the aqueous solution. Therefore, the toxic side effects caused by the charge can be eliminated.
(3) Water solubility: The non ionic contrast medium introduces multiple hydrophilic side chains containing hydroxyl groups into the benzene ring. It has symmetrical spatial distribution and it is surrounded the iodine atom, which can remove the ionic toxicity. Also, the hydroxyl group on the side chain ensures strong water solubility.
(4) Viscosity: Due to the good water solubility, it disperses quickly in the blood and is not easy to aggregate. Therefore, it rarely causes microvascular obstruction.