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Tests and Procedures

Computed Tomography (CT or CAT) Scan of the Spine

(Spinal CT Scan, CT of the Spine or Back)

Procedure overview

What is a CT or CAT scan of the spine?

Computed tomography (CT or CAT scan) is a noninvasive diagnostic imaging procedure that uses a combination of X-rays and computer technology to produce horizontal, or axial, images (often called slices) of the body. 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 much information can be obtained from a standard X-ray, a lot of detail about internal organs and other structures is not available.

In computed tomography, the 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 be seen more clearly. Contrast examinations may require you to fast for a certain period of time before the procedure. Your physician will notify you of this prior to the procedure.

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

Other related procedures that may be used to diagnose problems of the spine include X-rays, magnetic resonance imaging (MRI) of the spine, and positron emission tomography (PET) scan of the spine. Please see these procedures for additional information.

Anatomy of the spinal column
Click image to enlarge

Anatomy of the spine

The spinal column is made up of 33 vertebrae that are separated by spongy disks and classified into distinct areas.

  • The cervical area consists of seven vertebrae in the neck.

  • The thoracic area consists of 12 vertebrae in the chest area.

  • The lumbar area consists of five vertebrae in the lower back area.

  • The sacrum has five, small fused vertebrae.

  • The four coccygeal vertebrae fuse to form one bone, called the coccyx or tailbone.

The spinal cord, a major part of the central nervous system, is located in the vertebral canal and reaches from the base of the skull to the upper part of the lower back. The spinal cord is surrounded by the bones of the spine and a sac containing cerebrospinal fluid. The spinal cord carries sense and movement signals to and from the brain and controls many reflexes.

Reasons for the procedure

A CT scan of the spine may be performed to assess the spine for a herniated disk, tumors and other lesions, the extent of injuries, structural anomalies such as spina bifida (a type of congenital defect of the spine), blood vessel malformations, or other conditions, particularly when another type of examination, such as X-rays or physical examination, is not conclusive. CT of the spine may also be used to evaluate the effects of treatment of the spine, such as surgery or other therapy.

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

Risks of the procedure

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

If you are pregnant or suspect that you may be pregnant, you should notify your physician. Radiation exposure during pregnancy may lead to birth defects. If it is necessary for you to have a CT of the spine, special precautions will be made 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. Patients who are allergic to or sensitive to medications should notify their physician. Studies show that 85 percent of the population will not experience an adverse reaction from iodinated contrast; however, you will need to let your physician know if you have ever had a reaction to any contrast dye, and/or any kidney problems. A reported seafood allergy is not considered to be a contraindication for iodinated contrast.

Patients with kidney failure or other kidney problems should notify their physician. In some cases, the contrast dye can cause kidney failure. The effects of kidney disease and contrast agents have attracted increased attention over the last decade, as patients with kidney disease are more prone to kidney damage after contrast exposure. Also, patients taking the diabetes medication metformin (Glucophage) should alert their doctor before having IV contrast, as it may cause a rare condition called metabolic acidosis. If you take metformin, you will be asked to stop taking it at the time of the procedure and then wait for 48 hours after your injection. A blood test to check kidney function may be required before you can start taking metformin again. 

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

Before the procedure

  • Your physician will explain the procedure to you and offer you the opportunity to ask any questions that you might have about the procedure.

  • If your procedure 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 something is not clear.

  • Notify 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 requirement prior to a CT scan, unless a contrast dye is to be used. Your physician will give you special instructions ahead of time if contrast is to be used and if you will need to withhold food and drink.

  • Notify the technologist if you are pregnant or suspect you may be pregnant.

  • Notify the technologist if you have any body piercing on your chest and/or abdomen.

  • Based upon your medical condition, your physician may request other specific preparation.

During the procedure

Photo of person in CT scanner
CT scanner

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

Generally, a CT scan of the bones, joints, and soft tissue 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 procedure done with contrast, an intravenous (IV) line will be started in the hand or arm for injection of the contrast dye. For oral contrast, you will be given medication to swallow.

  4. You will lie on a scan table that slides into a large, circular opening of the scanning machine. Pillows and straps may be used to prevent movement during the procedure.

  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 enable the technologist to communicate with and hear you. You will have a call button so that you can let the technologist know if you have any problems during the procedure. 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 the body for short amounts of time. You will hear clicking 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 remain very still during the procedure. You may be asked to hold your breath at various times during the procedure.

  9. If contrast dye is used for your procedure, 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 administered.

  10. If contrast dye is used for your procedure, you may feel some effects when the dye is injected into the IV line. These effects include a flushing sensation, a salty or metallic taste in the mouth, a brief headache, or nausea and/or vomiting. These effects usually last for a few moments.

  11. You should notify 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 for contrast administration, the line will be removed.

  14. You may be asked to wait for a short period of 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 cause some discomfort or pain, particularly in the case of a recent injury or invasive procedure such as surgery. The technologist will use all possible comfort measures and complete the procedure as quickly as possible to minimize any discomfort or pain.

After the procedure

If contrast dye was used during your procedure, you may be monitored for a period of time for any side effects or reactions to the contrast dye, such as itching, swelling, rash, or difficulty breathing. Notify the radiologist or your physician if you experience any of these symptoms.

If you notice any pain, redness, and/or swelling at the IV site after you return home following your procedure, you should notify your physician as this could indicate an infection or other type of reaction.

Otherwise, there is no special type of care required after a CT scan of the spine. You may resume your usual diet and activities unless your physician advises you differently.

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

Online resources

The content provided here is for informational purposes only, and was not designed to diagnose or treat a health problem or disease, or replace the professional medical advice you receive from your physician. Please consult your physician with any questions or concerns you may have regarding your condition.

This page contains links to other websites with information about this procedure and related health conditions. We hope you find these sites helpful, but please remember we do not control or endorse the information presented on these websites, nor do these sites endorse the information contained here.

American Academy of Neurological and Orthopaedic Surgeons

American Academy of Orthopaedic Surgeons

American Cancer Society

American Society of Radiologic Technologists

Arthritis Foundation

National Cancer Institute (NCI)

National Institute of Child Health and Human Development

National Institute of Neurological Disorders and Stroke

National Institutes of Health (NIH)

National Library of Medicine

Radiological Society of North America

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