Computed tomography (CT) is a type of medical imaging test that uses special x-ray equipment to make detailed pictures of the inside of your body.

A CT scan produces cross-sectional pictures, which are like slices of the body. These images show the size and structure of organs, bones, and other tissues. CT images can also be combined to create 3-dimensional (3D) views.

Health care providers use CT scans to diagnose, treat, and monitor many health conditions.

Your provider may suggest a CT scan for many reasons, including:

• Fractures (broken bones)
• Cancer
• Tumors or masses
• Blood clots
• Signs of heart disease
• Spinal conditions
• Lung disease

CT scans may also be used to find the best place to perform a biopsy or help guide certain treatments. They may also be used to check for internal bleeding or injury after trauma or to evaluate the brain for certain conditions.

You may be asked not to eat or drink for a few hours before the scan. Ask your provider if there are any special instructions to follow.

For some CT scans, you may receive a contrast material. Contrast helps certain parts of the body show up more clearly on the images. Depending on what area is being examined, contrast material might be given as:

• A liquid to swallow
• A shot (injection)
• An enema (placed into the rectum)

CT scans use ionizing radiation at levels higher than a standard x-ray, but the amount is kept as low as possible. Always tell your provider if you are pregnant or think you may be pregnant.

You may be asked to change clothes and remove jewelry or other items that could interfere with the scan.

During the scan, you lie still on a table. The table slowly passes through the center of a large donut-shaped machine. The x-ray tube rotates around your body to create images.

You may hear whirring sounds during the scan. You may be asked to hold your breath for short periods. The test is painless.

The scan usually takes a few minutes, but some may last up to 30 minutes, depending on the area being scanned.

Most people can return to normal activities right away. If you were given a contrast material, drinking fluids can help your body clear it.

A specialist called a radiologist reviews the images and shares the results with your provider.

NIH: National Cancer Institute