During X-ray examinations of the upper gastrointestinal tract, such as the esophagus or stomach, the doctor will give the examinee a contrast agent called barium sulfate suspension, which is a contrast agent prepared with barium sulfate powder and potable water in a certain proportion, and can help the doctor to better observe the tissue structure of the gastrointestinal tract, so as to determine whether there is a disease or not and to locate the location of the disease. In addition, there also exists a non-conventional contrast agent, in some special cases, the examinee can not completely exclude whether there is an absolute contraindication, another non-ionic iodine contrast agent will be used for the patient to drink.