Computer Tomography (CT)

A CT scan, also called computerized tomography, CAT Scan or just CT, combines a series of X-ray views taken from many different angles to produce cross-sectional images of the bones and soft tissues inside your body.

The resulting images can be compared to a loaf of sliced bread. Your doctor will be able to look at each of these slices individually or perform additional visualization to make 3-D images. CT scan images provide much more information than plain X-rays.

A CT scan is particularly well-suited to quickly examine people who may have internal injuries from car accidents or other types of trauma. A CT scan can also visualize the brain and — with the help of injected contrast material — check for blockages or other problems in your blood vessels.

Why It’s Done

Your doctor may recommend a CT scan to help:

  • Diagnose muscle and bone disorders, such as bone tumors and fractures
  • Pinpoint the location of a tumor, infection or blood clot
  • Guide procedures such as surgery, biopsy and radiation therapy
  • Detect and monitor diseases such as cancer or heart disease
  • Detect internal injuries and internal bleeding

How You Prepare

How you prepare for a CT scan depends on which part of your body is being scanned. You may be asked to remove your clothing and wear a hospital gown. You’ll need to remove any metal objects, such as jewelry, that might interfere with image results.

Contrast Material

A contrast material is needed for some CT scans to help highlight the areas of your body being examined. The contrast material blocks X-rays and appears white on images, which can help emphasize blood vessels, bowel or other structures.

Contrast material can enter your body in a variety of ways:

  • Oral – If your esophagus, stomach or bowel is being scanned, you may need to swallow a drink that contains contrast material. This drink may taste unpleasant and cause temporary mild diarrhea.
  • Injection – Contrast agents can be injected into an intravenous line, to help view structures which have blood flowing through them, such as your internal organs, urinary tract, lungs and blood vessels. You may experience a feeling of warmth during the injection, or a metallic taste in your mouth.
  • Rectal – A gastrografin (iodine-based contrast) enema is a type of contrast material that helps visualize your intestines. It can make you feel bloated and uncomfortable. This contrast route is used for patients that are not able to drink oral contrast and must be ordered by a physician.

To properly visualize some areas, you may need to fast for a period of time beforehand.

Reactions to Contrast Material

Although rare, the intravenous (IV) contrast material involved in some CT scans causes medical problems or allergic reactions in some people. Most reactions are mild and result in hives or itchiness. In rare instances, an allergic reaction can be serious and potentially life-threatening. Make sure to tell your doctor if you’ve ever had a prior reaction to IV contrast material during medical tests.

Your risk of having a problem due to IV contrast may increase if you have a history of:

  • Heart disease
  • Asthma
  • Diabetes
  • Kidney disease
  • Multiple myeloma

What You Can Expect

You can have a CT scan done in a hospital or an outpatient facility. CT scans are painless and, with newer machines, typically take only a few minutes to complete.

During the CT Scan

CT scanners are shaped like a large doughnut standing on its side. You lie on a narrow table that slides into the “doughnut hole,” which is called a gantry. Straps and pillows may help you stay in position. During a CT scan of the head, the table may be fitted with a special cradle that holds your head still.

As the X-ray tube rotates around your body, the table slowly moves through the gantry. While the table is moving, you may need to hold your breath to avoid blurring the images. You may hear clicking and whirring noises. Each rotation yields several images of thin slices of your body.

A technologist will be nearby, in a separate room. You will be able to communicate with the technologist via intercom.

After the CT Scan

After the exam you can return to your normal routine. If you were given a contrast material, your doctor, a nurse or the CT technologist performing the scan may give you special instructions. You may be asked to wait for a short time in the radiology department to ensure that you feel well after the exam. After the scan, you’ll likely be told to drink lots of fluids to help your kidneys remove the contrast material from your body.


CT images are stored as electronic data files and usually reviewed on a computer. A radiologist interprets these images and sends a report to your doctor.

Preparing Your Small Child for a Scan

If your infant or toddler is having the CT scan, the doctor may give your child a sedative to keep him or her calm and still. Movement blurs the images and may lead to inaccurate results. Ask your doctor how best to prepare your child.


During a CT scan, you’re briefly exposed to much more radiation than you would be during a plain X-ray. Radiation exposure potentially increases your risk of developing cancer, but doctors and other scientists believe that CT scans provide enough valuable information to outweigh their potential risks.

Be sure to inform your doctor if you’re pregnant. He or she may recommend another type of exam, such as ultrasound or magnetic resonance imaging (MRI), to avoid the risk of exposing your fetus to the radiation.

Acceptable dose amounts of radiation produced by imaging equipment are set by the United States government and are installed as such by the equipment’s manufacturer. Providence Healthcare Network employs a physicist from an outside entity to inspect our equipment regularly. This helps insure that the minimum amount of radiation dose possible is used to acquire clear and diagnostic images for your tests.