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 as your body moves through the scanner in small increments.

A computer creates separate images of the body area. These are called slices. These images can be stored, viewed on a monitor, or printed on film. The slices together can create three-dimensional models of the body area.

You must be still during the exam. Movement will create blurred images. You may be told to hold your breath for short periods of time.

The scan should take only 10 to 15 minutes.

Certain exams require a special dye, called contrast. Contrast is delivered into the body before the test starts. This helps certain areas show up better on the x-rays.

Contrast can be given in several ways. It may be given as an injection through:

• A vein (IV) in your hand or forearm
• Your back into the space surrounding the spinal cord
• A joint if one is under investigation

If contrast is used, you may also be asked not to eat or drink anything for 4 to 6 hours before the test.

Before receiving the contrast, tell your health care provider if:

• You have ever had a reaction to contrast. You may need to take medicines before the test to safely receive the dye.
• You take the diabetes medicine metformin (Glucophage). You may need to take extra steps if you take this medicine.

Find out if the CT machine has a weight limit if you weigh more than 450 pounds (200 kilograms). Too much weight can cause damage to the scanner.

You will be asked to remove jewelry and wear a hospital gown during the study.

Some people may find it uncomfortable to lie on the hard table.

Contrast given through an IV may cause:

• Slight burning feeling
• Metallic taste in the mouth
• Warm flushing of the body

These feelings are normal and will often go away within a few seconds.

CT rapidly creates detailed pictures of the thoracic spine. The test may help diagnose or detect:

• Birth defects of the spine in children
• Bone fracture in the spine
• Arthritis of the spine
• Curvature of the spine called scoliosis
• Tumor of the spine
• Other spinal injury

Thoracic CT scan can also be used during or after:

• Myelography: An x-ray of the spinal cord and spinal nerve roots with contrast in the space around the spinal cord
• Discography: An x-ray of the disk

Results are normal if the thoracic spine looks normal.

Abnormal results may be due to:

• Birth defects of the spine
• Bone problems
• Fracture
• Herniated (slipped) disk
• Infection of the spine
• Narrowing of the spine (spinal stenosis)
• Scoliosis
• Tumor

Risks of CT scans include:

• Exposure to radiation
• Allergic reaction to contrast dye

CT scans expose you to more radiation than regular x-rays. Having many x-rays or CT scans over time may increase your risk for cancer. However, the risk from any one scan is small. You and your provider should weigh this risk against the benefits of getting a correct diagnosis for a medical problem.

Some people have allergies to contrast dye.

The most common type of contrast given into a vein contains iodine. People with an iodine allergy may have:

• Nausea or vomiting
• Sneezing
• Itching or hives

In case you are allergic, your provider may give you antihistamines (such as Benadryl) or steroids before the test.

The kidneys help remove the dye from the body. People with kidney disease or diabetes may need to receive extra fluids after the test. This will help flush the dye out of the body. Be sure to tell your provider if you have any kidney problems.

Rarely, the dye may cause anaphylaxis. Notify the scanner operator right away if you have any trouble breathing or swallowing. Scanners come with an intercom and speakers, so the operator can hear you at all times.

The thoracic CT scan is good for evaluating large herniated disks. It can miss the smaller ones. This test with a myelogram will show a better image of the nerve roots and find smaller injuries or abnormalities.

CAT scan - thoracic spine; Computed axial tomography scan - thoracic spine; Computed tomography scan - thoracic spine; CT scan - upper back

Rankine JJ. Spinal trauma. In: Adam A, Dixon AK, Gillard JH, Schaefer-Prokop CM, eds. Grainger & Allison's Diagnostic Radiology: A Textbook of Medical Imaging. 7th ed. Philadelphia, PA: Elsevier; 2021:chap 52.

US Food and Drug Administration website. Computed tomography (CT). www.fda.gov/radiation-emitting-products/medical-x-ray-imaging/computed-tomography-ct. Updated January 5, 2023. Accessed July 9, 2024.

Williams KD. Fractures, dislocations, and fracture-dislocations of the spine. In: Azar FM, Beaty JH, eds. Campbell's Operative Orthopaedics. 14th ed. Philadelphia, PA: Elsevier; 2021:chap 41.

Updated by: C. Benjamin Ma, MD, Professor, Chief, Sports Medicine and Shoulder Service, UCSF Department of Orthopaedic Surgery, San Francisco, CA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.