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Thoracic CT |
| Definition: |
| A CT scan (computed tomography) of the chest and upper abdomen. |
| Alternative Names: |
| Chest CT; CT scan - lungs; CT scan - chest |
| How the test is performed: |
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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: |
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The health care provider may advise fasting of solids and liquids for 4 to 6 hours 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 for weights greater than 300 pounds. Since metal is very, very dense, the X-ray beam has difficulty passing through it and results in errors in the involved constructed slices (artifact). Therefore, the patient may be asked to remove jewelry and wear a hospital gown during the study.
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| How the test will feel: |
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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 reside within a few seconds. |
| 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: |
| What the risks are: |
| 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, sneezing, vomiting, itching, or hives. In people who are sensitive to iodine, the dye may occasionally cause anaphylaxis (life-threatening allergic response) or toxic effects to the kidneys. |
| Special 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. |
Reviewed By: Evan Mair, M.D., Department of Radiology, Boston Medical Center, Boston, MA. Review provided by VeriMed Healthcare Network
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