CT Scans: What They Show, Why You Might Need One, and What to Expect

Computed tomography (CT) is a medical imaging test that uses special X-ray equipment to make detailed pictures of the inside of the body. A CT scan produces cross-sectional images — like slices of the body — that show the size and structure of organs, bones and other tissues. The images can also be combined into 3D views.

Why you might have one

Providers use CT scans to diagnose, treat and monitor many conditions, including:

• fractures (broken bones);
• cancer, tumors or masses;
• blood clots;
• signs of heart disease;
• spinal conditions;
• lung disease.

CT can also show where to do a biopsy, help guide some treatments, check for internal bleeding or injury after trauma, and look at the brain for certain conditions.

Getting ready

• You may be asked not to eat or drink for a few hours beforehand; ask about any special instructions.
• Some scans use contrast material, which makes certain parts of the body show up more clearly — given as a drink, an injection, or an enema.
• CT uses ionizing radiation, at higher levels than a standard X-ray, though the dose is kept as low as possible. Always tell your provider if you are or might be pregnant.

During the scan

• You may change clothes and remove jewelry or other items that could interfere.
• You lie still on a table that slides slowly through a large donut-shaped machine, while an X-ray tube rotates around you. You may hear whirring, and be asked to hold your breath briefly.
• It is painless. Most scans take a few minutes; some last up to 30 minutes, depending on the area.

Afterward

Most people go back to normal activities at once. If you had contrast, drinking fluids helps your body clear it. A radiologist reads the images and sends the results to your provider.

Sources

Based on "CT Scans," MedlinePlus, National Library of Medicine, drawing on the National Cancer Institute; a work of the United States government in the public domain.