PET-CT contrast agent is injected, not drunk, but you should drink more water before and after the examination, on the one hand, it can speed up the metabolism of the drug, shorten the retention time of the drug, and reduce the radiation damage; on the other hand, it can improve the quality of the image, and better distinguish between physiological uptake and pathological uptake. 1h after drug injection, drink about 500~1000ml of water (plain water or pure water) intermittently at a normal rate, part of which fills up the gastrointestinal tract to make the image clearer, and part of which enters into the kidneys to promote the excretion of the contrast agent that is not ingested; drink 300~500ml of water quickly before the examination to fill up the stomach as much as possible, and drink as much water as possible after the examination to promote the excretion of the contrast agent. If there are patients with lesions in the esophagus and stomach, or if they are physically weak and should not drink more water, they need to inform the doctor in a timely manner, so as not to be negligent, so as not to delay the condition.