Skip banner links and go to contentU.S. Department of Health & Human Services * National Institutes of Health
National Heart, Lung, and Blood Institute:  Diseases and Conditions Index
Tell us what you think about this site
  Enter keywords to search this site. (Click here for Search Tips)  
U.S. Department of Health & Human Services National Institutes of Health Diseases and Conditions Index NIH Home NHLBI Home About This Site NHLBI Home NHLBI Home Link to Spanish DCI Tell us what you think
 DCI Home: Lung Diseases: Chest CT Scan: What Is ...

      Chest CT Scan
Skip navigation and go to content
What Is ...
Other Names
Who Needs
What To Expect Before
What To Expect During
What To Expect After
What Does It Show
What Are the Risks
Key Points

What Is a Chest CT Scan?

A chest computed tomography (to-MOG-ra-fee), or CT, scan is a painless, noninvasive test. It creates precise images of the structures in your chest, such as your lungs. “Noninvasive” means that no surgery is done and no instruments are inserted into your body.

A chest CT scan is a type of x ray. However, a CT scan’s pictures show more details than pictures from a standard chest x ray.

Like other x-ray tests, chest CT scans use a form of energy called ionizing radiation. This energy helps create pictures of the inside of your chest.


Doctors use chest CT scans to:

  • Show the size, shape, and position of your lungs and other structures in your chest.
  • Follow up on abnormalities that are found on standard chest x rays.
  • Find the cause of lung symptoms, such as shortness of breath or chest pain.
  • See whether you have a lung problem, such as a tumor, excess fluid around the lungs, or a pulmonary embolism (PULL-mun-ary EM-bo-lizm; a blood clot in the lungs). The test also is used to check for other conditions, such as tuberculosis (tu-ber-kyu-LO-sis), emphysema (em-fi-SE-ma), and pneumonia.

The chest CT scanning machine takes many pictures, called slices, of the lungs and the inside of the chest. A computer processes these pictures; they can be viewed on a monitor or printed on film. The computer also can stack the pictures to create a very detailed, three-dimensional (3D) model of organs.

Sometimes, a special substance (called contrast dye) is injected into a vein in your arm. This substance highlights areas in your chest, which helps create clearer images.


Chest CT scans have few risks. Because the test uses radiation, there may be a slight risk of cancer.

Children are more sensitive to radiation than adults because they’re smaller and still growing.

The amount of radiation will vary with the type of CT scan. On average, though, the radiation will not exceed the amount a person is naturally exposed to over 3 years. The benefits of a CT scan should always be weighed against the possible risks.

Rarely, people have allergic reactions to the contrast dye that’s sometimes used for chest CT scans. If this happens, your doctor will give you medicine to relieve the symptoms.

March 2008


Email this Page Email all Sections Print all Sections Print all Sections of this Topic

Skip bottom navigation and go back to top
Department of Health and Human Services National Institutes of Health National Heart, Lung, and Blood Institute
Blood Diseases | Heart and Blood Vessel Diseases | Lung Diseases | Sleep Disorders
NHLBI Privacy Statement | NHLBI Accessibility Policy
NIH Home | NHLBI Home | DCI Home | About DCI | Search
About NHLBI | Contact NHLBI

Note to users of screen readers and other assistive technologies: please report your problems here.