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 models of the body area can be created by stacking the slices together.
You must be still during the exam, because movement causes blurred images. You may be told to hold your breath for short periods of time.
The scan should take only 10-15 minutes.
How to Prepare for the Test
Certain exams require a special dye, called contrast, to be delivered into the body before the test starts. Contrast helps certain areas show up better on the x-rays.
Contrast can be given in several ways.
It may be delivered through a vein (IV) in your hand or forearm.
It may be given as an injection into the space surrounding the spinal cord.
If contrast is used, you may also be asked not to eat or drink anything for 4-6 hours before the test.
Tell your doctor nurse if you have ever had a reaction to contrast. You may need to take medicines before the test in order to safely receive this substance.
Before receiving the contrast, tell your health care provider if you take the diabetes medication 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. 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 a slight burning feeling, a metallic taste in the mouth, and a 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 or middle part of the spine. The test may help diagnose or detect:
Birth defects of the spine in children
Bone fracture in the spine
Arthritis of the spine
Tumor of the spine
Other spinal injury
Thoracic CT scan can also be used during or after an x-ray of the spinal cord and spinal nerve roots (myelography) or an x-ray of the disk (discography).
Results are considered normal if the thoracic region is normal in appearance.
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 health care 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. If a person with an iodine allergy is given this type of contrast, nausea or vomiting,sneezing, itching,or hives may occur.
If you absolutely must be given such contrast, your health care provider may give you antihistamines (such as Benadryl) or steroids before the test.
The kidneys help remove iodine out of the body. Those with kidney disease or diabetes may need to receive extra fluids after the test to help flush the iodine out of the body.
Rarely, the dye may cause a life-threatening allergic response called anaphylaxis. Notify the scanner operator right away if you have any trouble breathing. 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, but it can miss smaller ones. This test can be combined with a myelogram to get a better image of the nerve roots and find smaller injuries.
RJ Gardocki, FX Camillo. Other disorders of the spine. In: Canale ST, Beaty JH, eds. Campbell's Operative Orthopaedics. 12th ed. Philadelphia, Pa: Mosby Elsevier; 2012:chap 44.
C. Benjamin Ma, MD, Assistant Professor, Chief, Sports Medicine and Shoulder Service, UCSF Department of Orthopaedic Surgery. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.