A computed tomography (CT) scan of the thoracic spine is an imaging method. This uses x-rays to rapidly create detailed pictures of the middle back (thoracic spine).
How the Test is Performed
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. 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.
How to Prepare for the Test
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.
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 300 pounds (135 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.
How the Test will Feel
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.
Why the Test is Performed
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
- 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
- Discography: An x-ray of the disk
Results are normal if the thoracic spine looks normal.
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 1 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:
In case you are allergic, your provider may give you antihistamines (such as Benadryl) or steroids before the test.
The kidneys help remove iodine out of the body. People with kidney disease or diabetes may need to receive extra fluids after the test. This will help flush the iodine out of the body.
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.
CAT scan - thoracic spine; Computed axial tomography scan - thoracic spine; Computed tomography scan - thoracic spine; CT scan - upper back
RJ Gardocki, FX Camillo. Other disorders of the spine. In: Canale ST, Beaty JH, eds. Campbell's Operative Orthopaedics. 12th ed. Philadelphia, PA: Elsevier Mosby; 2013:chap 44.
US Food and Drug Administration. Computed tomography (CT). Updated August 7, 2014. www.fda.gov/Radiation-EmittingProducts/RadiationEmittingProductsandProcedures/MedicalImaging/MedicalX-Rays/ucm115317.htm#4. Accessed April 25, 2016.
Review Date 3/10/2016
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 Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.