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CT scan
CT scan


Thyroid cancer - CT scan
Thyroid cancer - CT scan


Pulmonary nodule, solitary - CT scan
Pulmonary nodule, solitary - CT scan


Lung mass, right upper lobe - CT scan
Lung mass, right upper lobe - CT scan


Bronchial cancer - CT scan
Bronchial cancer - CT scan


Lung mass, right lung - CT scan
Lung mass, right lung - CT scan


Lung nodule, right lower lung - CT scan
Lung nodule, right lower lung - CT scan


Lung with squamous cell cancer - CT scan
Lung with squamous cell cancer - CT scan


Vertebra, thoracic (mid back)
Vertebra, thoracic (mid back)


Normal lung anatomy
Normal lung anatomy


Thoracic CT

Definition:

Thoracic CT (computed tomography) is an imaging method that uses x-rays to create cross-sectional pictures of the chest and upper abdomen.



Alternative Names:

Chest CT; CT scan - lungs; CT scan - chest



How the test is performed:

You will be asked to lie on a narrow table that slides into the center of the scanner.

Once you are inside the scanner, the machine's x-ray beam rotates around you.

Small detectors inside the scanner measure the amount of x-rays that make it through the part of the body being studied. A computer takes this information and uses it to create several individual images, called slices. These images can be stored, viewed on a monitor, or printed on film. Three-dimensional images of organs can be created by stacking the individual slices together.

You must be still during the exam, because movement causes blurred images. You may be told to hold your breath for short periods of time.

Generally, complete scans take only a few minutes. The newest multidetector scanners can image your entire body in less than 30 seconds.

Certain CT scans  require a special dye, called contrast, to be delivered into the body before the test starts. Contrast can highlight specific areas inside the body, which creates a clearer image. If your doctor requests a CT scan with contrast, you will be given it through a vein (IV) in your arm or hand.



How to prepare for the test:

Some people have allergies to IV contrast and may need to take medications before their test in order to safely receive this substance.

Contrast can be given several ways, and depends on the type of CT being performed.

  • It may be delivered through a vein (IV) in your hand or forearm.
  • It may be given through the rectum using an enema.
  • You might drink the contrast before your scan. When you actually drink the contrast depends on the type of exam being done. The contrast liquid may taste chalky, although some are flavored to make it taste a little better. The contrast eventually passes out of your body through your stools.

If contrast is used, you may also be asked not to eat or drink anything for 4-6 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 cause damage to the scanner's working parts.

Since x-rays have difficulty passing through metal, you will be asked to remove jewelry and wear a hospital gown during the study.



How the test will feel:

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.



Why the test is performed:

CT rapidly creates detailed pictures of the body, including the brain, chest, spine, and abdomen. The test may be used to better view the structures inside the chest.

A thoracic CT may be done:

  • After a chest injury
  • When a tumor or mass (clump of cells) is suspected
  • To determine the size, shape, and position of organs in the chest and upper abdomen
  • To look for bleeding or fluid collections in the lungs or other areas


Normal Values:



What abnormal results mean:

Thoracic CT may show many disorders of the heart, lungs, or chest area, including:

Additional conditions under which the test may be performed:



What the risks are:

CT scans and other x-rays are strictly monitored and controlled to make sure they use the least amount of radiation. CT scans do use low levels of ionizing radiation, which has the potential to cause cancer and other defects. However, the risk associated with any individual scan is small. The risk increases as numerous additional studies are performed.

In some cases, a CT scan may still be done if the benefits greatly out weigh the risks. For example, it can be more risky not to have the exam, especially if your health care provider thinks you might have cancer.

An abdominal CT scan is usually not recommended for pregnant women, because it may harm the unborn child. Women who are or may be pregnant should speak with their health care provider to determine if ultrasound can be used instead.

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. Rarely, the dye may 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.



Special considerations:

A CT scan is one of the best ways of looking at soft tissues such as the heart and lungs.



References:

Gotway MB, Elicker BM. Radiographic techniques. In: Mason RJ, Broaddus CV, Martin TR, et al. Murray & Nadel's Textbook of Respiratory Medicine. 5th ed. Philadelphia, Pa: Saunders Elsevier; 2010:chap 19.

Stark P. Imaging in pulmonary disease. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier;2011:chap 84.




Review Date: 9/1/2012
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.
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