Skeletal System

A computed tomography (CT) scan of the thoracis spine is an imaging method that uses x-rays to create cross-sectional pictures of the upper back (thoracic spine).

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

You will be asked to 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.

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.

Let your doctor know if you have ever had a reaction to contrast. You may need to take medications 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) because you may need to take extra precautions.

If you weigh more than 300 pounds, find out if the CT machine has a weight limit. Too much weight can cause damage to the scanner's working parts.

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

Some people may have discomfort from lying on the hard table.

Contrast given through an IV may cause a slight burning sensation, a metallic taste in the mouth, and a warm flushing of the body. These sensations are normal and usually go away within a few seconds.

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
• Spinal injury
• Other spine problems, when MRI cannot be used

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.

Abnormal results may be due to:

• Birth defects of the spine
• Bone problems
• Fracture
• Thoracic disk herniation
• Thoracic spinal stenosis
• Spondylolisthesis

Risks of CT scans include:

• Being exposed to radiation
• Allergic reaction to contrast dye

CT scans do 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 doctor should weigh this risk against the benefits of getting a correct diagnosis for a medical problem.

Some people have allergies to contrast dye. Let your doctor know if you have ever had an allergic reaction to injected 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 doctor 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. If you have any trouble breathing during the test, you should notify the scanner operator immediately. 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 pick up smaller injuries.

Curlee PM. Other disorders of the spine. In: Canale ST, Beaty JH. Campbell's Operative Orthopaedics. 11th ed. Philadelphia, Pa: Mosby Elsevier;2007:chap 21.

Review Date: 01/27/2010

David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc. Previously reviewed by Benjamin Taragin, MD, Department of Radiology, Montefiore Medical Center, Bronx, NY. Review provided by VeriMed Healthcare Network (2/9/2009).