Thoracic CT (computed tomography) is an imaging method that uses x-rays to create cross-sectional pictures of the chest and upper abdomen.
The test is done in the following way:
The complete scan takes 30 seconds to a few minutes.
Certain CT scans require a special dye, called contrast, to be delivered into the body before the test starts. Contrast highlights specific areas inside the body and creates a clearer image. If your doctor requests a CT scan with intravenous contrast, you will be given it through a vein (IV) in your arm or hand. A blood test to measure your kidney function may be done before the test. This test is to make sure your kidneys are healthy enough to filter the contrast.
Some people have allergies to IV contrast and may need to take medications before their test to safely receive this substance.
Contrast can be given in several ways, depending on the type of CT being performed.
If contrast is used, you may also be asked not to eat or drink anything for 4 to 6 hours before the test.
If you weigh more than 300 pounds, have your doctor contact the scanner operator before the exam. CT scanners have a weight limit. Too much weight can damage the scanner's working parts.
Because it is hard for x-rays to pass through metal, you will be asked to remove jewelry and wear a hospital gown during the study.
Some people may have discomfort from lying on the hard table.
Contrast given through an IV may cause a slight burning sensation, a metallic taste in the mouth, and a warm flushing of the body. These sensations are normal and usually go away within a few seconds.
There is no recovery time, unless you were given medicine to relax. After a CT scan, you can go back to your normal diet, activity, and medications.
CT quickly creates detailed pictures of the body. The test may be used to get a better view of the structures inside the chest.
A thoracic CT may be done:
Thoracic CT may show many disorders of the heart, lungs, or chest area, including:
Other conditions under which the test may be performed:
CT scans and other x-rays are strictly monitored and controlled to make sure they use the least amount of radiation. CT scans use low levels of ionizing radiation, which has the potential to cause cancer and other defects. However, the risk from any one scan is small. The risk increases as many more studies are done.
In some cases, a CT scan may still be done if the benefits greatly outweigh the risks. For example, it can be more risky to not have the exam if your doctor thinks you might have cancer.
The most common type of contrast given into a vein contains iodine. If a person with an iodine allergy is given this type of contrast, nausea, sneezing, vomiting, itching, or hives may occur. In rare cases, the dye can cause a life-threatening allergic response called anaphylaxis. If you have any trouble breathing during the test, you should notify the scanner operator immediately. Scanners come with an intercom and speakers, so the operator can hear you at all times.
In people with kidney problems, the dye may have harmful effects on the kidneys. In these situations, special steps may be taken to make the CT scan safer.
A CT scan is one of the best ways of looking at soft tissues such as the heart and lungs.
Chest CT; CT scan - lungs; CT scan - chest
Gotway MB, Elicker BM. Radiographic techniques. In: Mason RJ, Broaddus CV, Martin TR, et al, eds. Murray & Nadel's Textbook of Respiratory Medicine. 5th ed. Philadelphia, PA: Elsevier Saunders; 2010:chap 19.
Stark P. Imaging in pulmonary disease. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 84.
Updated by: Denis Hadjiliadis, MD, Associate Professor of Medicine, Pulmonary, Allergy, and Critical Care, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.
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