Doctors perform CT scans of the lungs to seek evidence of lung conditions such as tuberculosis, find causes of lung symptoms, and follow up on abnormal chest X-ray findings, states the National Heart, Lung, and Blood Institute. They see the lungs' shape, size and position clearly using a noninvasive method.
Chest CT scans, also known as lung imaging tests or computed axial tomography, or CAT, scans, are painless and non-invasive with only a slight risk of radiation, adds the NHLBI. After taking X-ray pictures of the lungs and chest interior with a large, tunnel-shaped scanner, a computer uses the information to create series of pictures called slices. There are two types of CT scans: the high-resolution scan, which provides numerous razor-thin slices with a single rotation, and the spiral chest or helical scan, where the X-ray beam follows a spiral pattern as it rotates.
Chest CT scans provide a more detailed picture of the lungs than standard X-rays, can pinpoint a tumor, and may show something that is not visible in an X-ray, explains the NHLBI. Thus, doctors recommend them to patients who have breathing trouble or chest pain or who show other symptoms of lung problems when X-rays are unable to help with the diagnosis.