CT scan

A CT scan, also called computed tomography or just CT, combine 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.

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, can 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

It can depend on which part of your body is being scanned. You may be asked to remove your clothing and wear a hospital gown. You will 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, bowels or other structures.

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

  • Orally: If your esophagus or stomach is being scanned, you may need to swallow a drink that contains material. This drink may taste unpleasant and may also cause diarrhea.
  • Injection: Contrast agents can be injected into an intravenous line to help view your gallbladder, urinary tract, liver or blood vessels. You may experience a feeling of warmth during the injection or notice a metallic taste in your mouth.

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

Preparing your small child for a scan

If your infant or toddler is having a CT scan, your 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.

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

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 will likely be told to drink lots of fluids to help your kidneys remove the contrast material from your body.

Results

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.

Safety

During a CT scan you are 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 are pregnant or if you think you might be 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. 

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