A chest CT scan is a more detailed type of chest x ray. This painless imaging test takes many detailed pictures, called slices, of your lungs and the inside of your chest. Computers can combine these pictures to create three-dimensional (3D) models to help show the size, shape, and position of your lungs and structures in your chest. This imaging test is often done to follow up on abnormal findings from earlier chest x rays. A chest CT scan also can help determine the cause of lung symptoms such as shortness of breath or chest pain, or check to see if you have certain lung problems such as a tumor, excess fluid around the lungs that is known as pleural effusion, pulmonary embolism, emphysema, tuberculosis, and pneumonia.
Your chest CT scan may be done in a medical imaging facility or hospital. The CT scanner is a large, tunnel-like machine that has a table. You will lie still on the table and the table will slide into the scanner. Talk to your doctor if you are uncomfortable in tight or closed spaces to see if you need medicine to relax you during the test. You will hear soft buzzing or clicking sounds when you are inside the scanner and the scanner is taking pictures. You will be able to hear from and talk to the technician performing the test while you are inside the scanner. For some diagnoses, a contrast dye, often iodine-based, may be injected into a vein in your arm before the imaging test. This contrast dye highlights areas inside your chest and creates clearer pictures. You may feel some discomfort from the needle or, after the contrast dye is injected, you may feel warm briefly or have a temporary metallic taste in your mouth.
Chest CT scans have some risks. In rare instances, some people have an allergic reaction to the contrast dye. There is a slight risk of cancer, particularly in growing children, because the test uses radiation. Although the amount of radiation from one test is usually less than the amount of radiation you are naturally exposed to over three years, patients should not receive more CT scans than the number that clinical guidelines recommend. Another risk is that chest CT scans may detect an incidental finding, which is something that doesn’t cause symptoms but now may require more tests after being found. Talk to your doctor and the technicians performing the test about whether you are or could be pregnant. If the test is not urgent, they may have you wait to do the test until after your pregnancy. If it is urgent, the technicians will take extra steps to protect your baby during this test. Let your doctor know if you are breastfeeding because contrast dye can pass into your breast milk. If you must have contrast dye injected, you may want to pump and save enough breast milk for one to two days after your test or you may bottle-feed your baby for that time.
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The National Heart, Lung, and Blood Institute (NHLBI) leads or sponsors many studies aimed at preventing, diagnosing, and treating heart, lung, blood, and sleep disorders.