CT (Computed Tomography) Scan

Written by Heather Ross | Published on August 15, 2012
Medically Reviewed by George Krucik, MD

What Is a CT Scan?

A computerized tomography scan (CT or CAT scan) is a series of cross-sectional X-ray images of your body. CT scans are used to examine your bones and soft tissues for damage or abnormalities. Often, these images can be combined to create a 3D picture of your body.

A CT scan can help your doctor:

  • diagnose infections and bone fractures
  • identify masses and tumors (including cancer)
  • study your blood vessels and other internal structures

The test is minimally invasive and can be conducted quickly.

How Is a CT Scan Performed?

Your doctor may give you a special dye called contrast to help structures such as blood vessels and intestines show up more clearly on the X-ray images. You may need to drink a liquid containing the contrast, or it may be injected into your arm or administered through your rectum via an enema, depending on the part of your body scanned. You may be asked to fast for four to six hours before the test if contrast is used.

When it comes time to have the CT scan, you’ll be asked to change into a hospital gown and remove your jewelry. (Metal will interfere with the image results.) Your doctor will ask you to lie on your back on a table that slides into the CT scanner. The machine’s X-ray beam will then rotate around you to capture the images.

It’s very important to lie still because movement can cause blurry images. If a small child needs a CT scan, the doctor may recommend a sedative to keep the child from moving. The technician who operates the scanner may ask you to hold your breath for a short time during the test to keep your chest from moving up and down.

What Are the Risks Associated with a CT Scan?

There are very few risks associated with this procedure. CT scans expose you to more radiation than typical X-rays, but the risk of cancer caused by radiation is very small if you’re having only one scan. Your risk of cancer may increase over time if you have multiple X-rays or CT scans.

Some people have an allergic reaction to the contrast dye. Let your doctor know if you’ve had this reaction in the past. Most contrast contains iodine. If you’re allergic to iodine, it may cause nausea, vomiting, sneezing, itching, or hives. Your doctor may administer allergy medication or steroids to counteract any potential side effects if you’re allergic to iodine but must be given contrast.

Tell the scanner operator if you have trouble breathing after being given the contrast. In rare cases, the contrast may trigger a severe allergic reaction called anaphylaxis that causes your airways to constrict.

What Do the Test Results Mean?

A radiologist will examine the images taken during the CT scan and send a report to your doctor. The results are considered normal if the radiologist doesn’t find any tumors, clots, fractures, or other abnormalities on the images. If the radiologist or your doctor finds anything abnormal during your scan, you may need further tests or treatments, depending on the type of abnormality.

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