Definition
Thoracic
CT is a computed tomography scan of the chest and upper abdomen.
Alternative Names
Chest CT; CT scan - lungs; CT scan - chest
Why the Test is Performed
Thoracic CT may be recommended when there is a need for examination of the structures inside the chest. It is
noninvasive and poses less risk than
invasive procedures (such as
angiography or exploratory surgery).
Common indications for thoracic CT include:
- when there is a chest injury
- when a tumor or mass (clump of cells) is suspected
- to determine the size, shape, and position of internal organs
- to look for bleeding or fluid collections in the lungs or other areas
How the Test is Performed
The patient will be asked to lie on a narrow table (gantry) that slides into the center of the scanner. Depending on the study being performed, the patient may need to lie on his/her stomach, back, or side. If contrast media (dye) is to be administered, intravenous access will be placed in a small vein of a hand or arm.
Much like standard photographic cameras, subject motion causes blurred images in CT. Therefore, the technologist operating the scanner and supervising the patient will give instructions through an intercom when to hold one's breath and not move.
As the exam takes place, the gantry will advance small intervals through the scanner. Modern "spiral" scanners can perform the examination in one continuous motion of the gantry. Generally, complete scans will only take a few minutes, however, additional contrast-enhanced or higher-resolution scans will add to the scan time. The newest multi-detector scanners can image the entire body, head to toe, in under 30 seconds.
How to Prepare for the Test
The health care provider may advise you to avoid eating or drinking for 4 to 6 hours prior to the scan, if contrast dye is to be used.
The CT scanner has a weight limit to prevent damage to the mechanized gantry. Have the health care provider contact the scanner operator if you weigh more than 300 pounds.
Metal interferes with the X-rays, so you may be asked to remove jewelry and wear a hospital gown during the study.
For infants and children:
The preparation you can provide for this test depends on your child's age and previous experience. For specific information regarding how you can prepare your child, see the following topics:
How the Test Will Feel
The X-rays are painless. The primary discomfort may be from the need to lie still on the table.
If intravenous contrast dye is given, the patient may initially feel a slight burning sensation within the injected arm, 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.
Risks
CT scans and other X-rays are monitored and regulated to provide the minimum amount of radiation exposure needed to reproduce the image. During pregnancy, a thoracic CT scan is not recommended unless the benefits outweigh the risk of radiation exposure to the fetus. CT scans provide low levels of radiation.
The most common dye used is iodine-based. A person who is allergic to iodine may experience nausea, vomiting, sneezing, itching, or hives, and occasionally
anaphylaxis (life-threatening
allergic response). In people with kidney problems, the dye may have toxic effects on the kidneys.
Considerations
The benefits of a CT scan usually far outweigh the risks of the X-rays. A CT scan is one of the best ways of "looking" at soft tissues such as the heart and lungs.
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:
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