Contrast medium is a liquid that contains iodine ions and helps to perform imaging examinations to clearly visualize blood vessels and other areas. Contrast medium is used only for enhanced CT, and also for various contrast examinations such as coronary angiography and intracranial angiography. The contrast medium is viscous and liquid, and contains elemental iodine, so that the vessels in the ducts are clearly visible under X-ray when the contrast medium is administered. When performing contrast examinations, patients need to be asked if they have a history of iodine allergy, and if there is a history of iodine allergy, they should be especially vigilant and perform that test and perform an iodine allergy test if necessary. Contrast agents are prone to have harmful effects on the thyroid gland and kidneys, especially in patients with hyperthyroidism, who are prone to induce hyperthyroid crisis after exposure to iodine-containing contrast agents, so screening for thyroid function should be perfected before performing the imaging. If hyperthyroidism is present, it should be treated first and only after the condition has stabilized should imaging-related tests be performed. Contrast agents can also affect the kidneys, especially in patients with abnormal kidney function, which can easily induce contrast nephropathy, so before and after contrast, hydration therapy should be performed.