To do a coronary CT test requires an intravenous injection of contrast agent, usually iodine contrast agent, such as iohexol and Uvexan. The contrast agent enters the body and is developed in the coronary arteries, and computer processing is performed on the coronary arteries to obtain a complete image of the coronary arteries. There is no uncomfortable symptom in the process of coronary CT itself. In the process of injection, a needle needs to be stuck in the hand and injected into the body through a high-pressure syringe, and the body will feel feverish for ten or several seconds, and the heart rate will speed up accordingly. But other than that, there is generally no discomfort, so it is not very uncomfortable to have a coronary CT. Some people may be more nervous, thinking that it may be more risky and more damaging to the body, and that the symptoms of anxiety may easily amplify the symptoms of discomfort, or even some people may not be well rested and scared the night before, so they may feel uncomfortable, but in fact, these are unnecessary. Because coronary CT itself is a non-invasive test designed to replace coronary angiography, it is much better than coronary angiography in terms of safety and comfort. A few people may have allergic reactions, mostly occurring about 5 minutes after drug injection. Minor reactions mainly manifest as hives, flushing, salivation, sneezing, lacrimation, chest tightness, shortness of breath, nausea, vomiting, etc. Most of them can be eliminated on their own within a short period of time without special treatment, and only in a very few cases may there be serious allergic reactions, or even shock, with life-threatening effects. In order to facilitate the observation of possible allergic reactions and other situations, patients are usually asked to leave the CT room 30 minutes after the examination, and they will be instructed to drink as much water as possible after the examination to promote the excretion of the contrast agent and reduce its impact on the body.