A computed tomography (CT) scan of the leg makes cross-sectional pictures of the leg. It uses x-rays to create the images.
You will lie on a narrow table that slides into the center of the CT scanner.
Once you are inside the scanner, the machine's x-ray beam rotates around you. (Modern "spiral" scanners can perform the exam without stopping.)
A computer creates separate images of the body area, called slices. These images can be stored, viewed on a monitor, or printed on film. Three-dimensional (3D) models of the leg can be created by adding the slices together.
You will need to lie still during the exam. Movement can cause blurred images. You may need to hold your breath for short periods of time.
The scan should take only 10 to 15 minutes.
Some exams use a special dye, called contrast, that is put into your body before the test starts. Contrast helps certain areas show up better on the x-rays.
Too much weight can cause damage to the scanner's working parts. Find out if the CT machine has a weight limit if you weigh more than 300 pounds (135 kilograms).
You will wear a hospital gown during the study. You will need to take off all jewelry.
Some people may be uncomfortable lying on the hard table.
Contrast given through an IV may cause a slight burning feeling, a metal taste in the mouth, and a warm flushing of the body. These feelings are normal and go away in a few seconds.
CT scan makes detailed pictures of the body very quickly. The test may help look for:
A CT scan may also be used to guide a surgeon to the right area during a biopsy.
Results are considered normal if the leg being examined looks OK.
Abnormal results may be due to:
Risks for CT scans include:
CT scans expose you to more radiation than regular x-rays. Having many x-rays or CT scans over time may raise your risk for cancer, but the risk from any one scan is small. Talk to your provider about this risk against the benefits of the test.
Some people have allergies to contrast dye. Let your provider know if you have ever had this type of reaction.
The dye may cause a life-threatening allergic response called anaphylaxis. This is rare. Tell the scanner operator right away if you have any trouble breathing during the test. Scanners come with an intercom and speakers, so the operator can hear you at all times.
Reviewed By: C. Benjamin Ma, MD, Professor, Chief, Sports Medicine and Shoulder Service, UCSF Department of Orthopaedic Surgery, San Francisco, CA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.