Cardiac CT is usually a choice between injecting a contrast agent or leaving an IV needle in place. 1. Injection of contrast agent: If a patient has a heart problem, he or she can go to the hospital for a cardiac CT examination. Before the examination, patients need to be injected with contrast agent in advance. The contrast agent may cause allergic reactions to some patients, and skin tests need to be routinely carried out before the drug is administered. If the patient has no usual abnormalities and has no abnormalities in liver or kidney function, intravenous injection of the contrast agent may be considered before the coronary CT scan. With the help of the contrast agent, the shape of the coronary arteries of the heart can be clearly seen after cardiac CT imaging, which helps to determine the location and severity of coronary artery disease of the heart. 2. Indwelling intravenous needle: About 5 ml of contrast agent is injected into the indwelling needle for sensitivity testing and is usually observed for 10-20 minutes. If there is no rash, itching or generalized allergy, the test can be performed. Lie flat on the CT table with the contrast-filled high-pressure syringe and indwelling needle attached. It is recommended to consult a doctor for relevant examinations in time and, depending on the specific situation, to carry out symptomatic treatment under the doctor’s guidance.