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What Is a Chest CT Scan?

A chest computed tomography (to-MOG-ra-fee) scan, or chest CT scan, is a painless, noninvasive test. It creates precise pictures 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 detail 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 abnormal findings from standard chest x rays.
  • Find the cause of lung symptoms, such as shortness of breath or chest pain.
  • Find out whether you have a lung problem, such as a tumor, excess fluid around the lungs, or a pulmonary embolism (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 (nu-MO-ne-ah).

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 screen or printed on film. The computer also can stack the pictures to create a very detailed, three-dimensional (3D) model of organs.

Sometimes, a substance called contrast dye is injected into a vein in your arm for the CT scan. 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 amount of 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 during chest CT scans. If this happens, medicine is given to relieve the symptoms.

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Last Updated: February 29, 2012