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Computed Tomography (CT or CAT) Scan of the Spine

What is a CT scan of the spine?

Computed tomography is an imaging test that uses X-rays and computer technology to produce horizontal, or axial, images (often called slices) of the body. It’s also called CT or CAT scan. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat, and organs. CT scans are more detailed than standard X-rays.

In standard X-rays, a beam of energy is aimed at the body part being studied. A plate behind the body part captures the variations of the energy beam after it passes through skin, bone, muscle, and other tissue. While doctors can get much information from a standard X-ray, it does not give a lot of detail about internal organs and other structures.

In a CT scan, an X-ray beam moves in a circle around the body. This allows many different views of the same organ or structure. The X-ray information is sent to a computer that interprets the X-ray data and displays it in a two-dimensional (2D) form on a monitor.

CT scans may be done with or without "contrast." Contrast refers to a substance taken by mouth or injected into an intravenous (IV) line that causes the particular organ or tissue under study to show up more clearly on the scan.

CT scans of the spine can provide more detailed information about the vertebrae (bones of the spine), the disks between the vertebrae, and other spinal structures and tissues than standard X-rays of the spine. CT scans can give health care providers more information related to injuries and/or diseases of the spine.

Why might I need a CT scan of the spine?

A CT scan of the spine may be used to check the spine for a herniated disk, tumors or other lesions, the extent of spinal injuries, structural defects such as spina bifida (a type of congenital defect of the spine), blood vessel malformations, or other conditions. A CT scan may be done when another type of exam, such as an X-ray or physical exam, does not provide enough information.

A CT of the spine may also be used to assess the effects of treatment of the spine, such as surgery or other therapy.

There may be other reasons for your doctor to recommend a CT scan of the spine.

What are the risks of a CT scan of the spine?

You may want to ask your doctor about the amount of radiation used during the CT scan and the risks related to your particular situation. It is a good idea to keep a record of your radiation exposure, such as previous CT scans and other types of X-rays, so that you can inform your doctor. Risks associated with radiation exposure may be related to the cumulative number of X-ray exams and/or treatments over a long period.

If you are pregnant or think you may be, tell your doctor. Radiation exposure during pregnancy may lead to birth defects. If it’s necessary for you to have a CT of the spine, special precautions will be taken to minimize the radiation exposure to the fetus.

Nursing mothers should wait 24 hours after contrast material is injected before resuming breastfeeding.

If contrast dye is used, there is a risk for allergic reaction to the dye. Tell your doctor if you are allergic to or sensitive to medications, contrast, or iodine.  Studies show that most people will not have an adverse reaction from contrast dye. But, you will need to let your doctor know if you have ever had a reaction to any contrast dye, and/or any kidney problems. A seafood allergy is not a contraindication for contrast.

Tell your doctor if you have any kidney problems. In some cases, the contrast dye can cause kidney failure. People with kidney disease are more prone to kidney damage after contrast exposure.

Alert your doctor before having IV contrast if you are taking the diabetes medication metformin (Glucophage). It may cause a rare condition called metabolic acidosis. If you take metformin, you will be asked to stop taking it 24 hours before and for 48 hours after your CT scan. A blood test may be needed before you can start taking it again.

There may be other risks depending on your specific medical condition. Be sure to discuss any concerns with your doctor prior to the procedure.

How do I get ready for a CT scan of the spine?

  • Your doctor will explain the procedure to you and give you a chance to ask questions.
  • If your CT scan involves the use of contrast dye, you will be asked to sign a consent form that gives permission to do the procedure. Read the form carefully and ask questions if anything is not clear.
  • Tell the technologist if you have ever had a reaction to any contrast dye, or if you are allergic to iodine.
  • Generally, there is no fasting (not eating) requirement prior to a CT scan, unless a contrast dye is to be used. Your doctor will give you special instructions ahead of time if contrast is to be used and if you will need to withhold food and drink.
  • Tell your doctor of all medications (prescribed and over-the-counter), vitamins, herbs, and supplements that you are taking.
  • Tell the technologist if you are pregnant or think you may be.
  • Tell the technologist if you have any body piercings on your chest and/or abdomen.
  • Based on your medical condition, your doctor may request other specific preparation.

What happens during a CT scan of the spine?

CT scans can be done on an outpatient basis or as part of your hospital stay. Procedures may vary depending on your condition and your doctor’s practices.

Generally, a CT scan of the spine follows this process:

  1. You will be asked to remove any clothing, jewelry, or other objects that may interfere with the procedure, such as eyeglasses, hairpins, dentures, and possibly hearing aids.
  2. If you are asked to remove clothing, you will be given a gown to wear.
  3. If you are to have a scan done with contrast, an intravenous (IV) line will be started in your hand or arm for injection of the contrast dye.
  4. You will lie on a narrow table that slides into a large, circular opening of the ring-shaped scanning machine. Pillows and straps may be used to help prevent movement during the scan.
  5. The technologist will be in another room where the scanner controls are located. However, you will be in constant sight of the technologist through a window. Speakers inside the scanner will allow the technologist to talk to you and hear you. You will have a call button so that you can let the technologist know if you have any problems during the scan. The technologist will be watching you at all times and will be in constant communication.
  6. The scanner will begin to rotate around you and X-rays will pass through your body for short amounts of time. You will hear clicking and whirring sounds, which are normal.
  7. The X-rays absorbed by the body's tissues will be detected by the scanner and transmitted to the computer. The computer will transform the information into an image to be interpreted by the radiologist.
  8. It will be important for you to stay very still during the scan. You may be asked to hold your breath for a short time at various times during the scan.
  9. If contrast dye is used, you will be removed from the scanner after the first set of scans has been completed. A second set of scans will be taken after the contrast dye has been given.
  10. If contrast dye is used, you may feel some effects when the dye is injected into the IV line. These effects include a warm flushing sensation, a salty or metallic taste in the mouth, a brief headache, and/or nausea. These effects usually only last for a few moments.
  11. Tell the technologist if you feel any breathing difficulties, sweating, numbness, or heart palpitations.
  12. When the procedure has been completed, you will be removed from the scanner.
  13. If an IV line was inserted, it will be removed.
  14. You may be asked to wait for a short time while the radiologist examines the scans to make sure they are clear.

While the CT procedure itself causes no pain, having to lie still for the length of the procedure might be uncomfortable, particularly if you’ve recently been injured or had surgery. The technologist will use all possible comfort measures and complete the procedure as quickly as possible to minimize any discomfort or pain.

What happens after a CT scan of the spine?

If contrast dye was used, you may be watched for a period for any side effects or reactions to the contrast dye, such as itching, swelling, rash, or difficulty breathing. Tell the radiologist or your doctor right away if you notice any of these symptoms.

If you notice any pain, redness, and/or swelling at the IV site after you go home, tell your doctor as this could be a sign of infection or other type of reaction.

Otherwise, there is no special type of care required after a CT scan of the spine. You may go back to your usual diet and activities unless your doctor tells you differently.

Your doctor may give you additional or alternate instructions after the procedure, depending on your particular situation.

Next steps

Before you agree to the test or the procedure make sure you know:
  • The name of the test or procedure
  • The reason you are having the test or procedure
  • The risks and benefits of the test or procedure
  • When and where you are to have the test or procedure and who will do it
  • When and how will you get the results
  • How much will you have to pay for the test or procedure
Online Medical Reviewer: Larson, Kim APRN, FNP
Online Medical Reviewer: MMI board-certified, academically affiliated clinician
Date Last Reviewed: 11/21/2013
© 2000-2015 The StayWell Company, LLC. 780 Township Line Road, Yardley, PA 19067. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.