Computed Tomography (CT) Scan of the Spine

A computed tomography (CT) scan uses X-rays to make detailed pictures of the spine and vertebrae in the neck (cervical spine), upper back (thoracic spine), or lower back (lumbosacral spine).

The spine is made of 33 bones, and most of the bones have discs that act as cushions in between the bones. The spinal cord is surrounded by the bones of the spine (vertebrae) and a sac holding cerebrospinal fluid (CSF).

During the test, you will lie on a table that is attached to the CT scanner, which is a large doughnut-shaped machine. The CT scanner sends X-rays through the body. Each rotation of the scanner takes a second and provides a picture of a thin slice of the organ or area being studied. One part of the scanning machine can tilt to follow the curve of your spine. All of the pictures are saved as a group on a computer. They also can be printed.

In some cases, a dye (contrast material) may be put in a vein (IV) in your arm or into the spinal canal (intrathecally). The dye make structures and organs easier to see on the CT pictures. The dye may be used to check blood flow and to look for tumors, areas of inflammation, or nerve damage.

See CT images of the cervical spine.

A CT scan of the spine is done to:

• Look at the bones of the spine (vertebrae).
• Find problems of the spine, such as tumors, fractures, deformities, infection, or narrowing of the spinal canal (spinal stenosis).
• Find a herniated disc of the spine.
• Check to see if osteoporosis has caused compression fractures.
• Check on problems of the spine that have been present since birth (congenital).
• Look at problems seen during a standard X-ray test.
• Check how well spinal surgery or therapy is working for a spine problem.

Before the CT scan, tell your doctor if you:

• Are or might be pregnant.
• Are breast-feeding. You will need to use formula for 1 to 2 days if you are given the dye so that you will not pass the dye to your baby. You should throw out any breast milk you collect during this time.
• Are allergic to any medicines, including iodine dyes or numbing medicines (anesthesia).
• Have a heart condition, such as heart failure.
• Have diabetes or take metformin (Glucophage) for your diabetes.
• Have had kidney problems.
• Have asthma.
• Have had thyroid problems.
• Have had multiple myeloma.
• Have had an X-ray test using barium contrast material (such as a barium enema) or have taken medicine that contains bismuth (such as Pepto-Bismol) in the past 4 days. Barium and bismuth show up on X-ray films and make it hard to see the picture clearly.
• Become very nervous in small spaces. You need to lie still inside the CT scanner, so you may need a medicine (sedative) to help you relax.

Arrange for someone to take you home in case you get a medicine to help you relax (sedative) for the test.

Talk to your health professional about any concerns you have regarding the need for the test, its risks, or how it will be done. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).

A CT scan is usually done by a radiology technologist. The pictures are usually read by a radiologist, who writes the report. Other doctors, such as a family medicine doctor, internist, or surgeon, may also review a CT scan.

You may need to take off any jewelry. You will need to take off all or most of your clothes. You may be able to wear your underwear for the scan. You will be given a gown to use during the test.

During the test, you will lie on a table that is attached to the CT scanner, which is a large doughnut-shaped machine.

The table slides into the round opening of the scanner, and the scanner moves around your body. The table will move while the scanner takes pictures. You may hear a click or buzz as the table and scanner move. It is very important to lie still during the test.

During the test, you may be alone in the scanning room. However, the technologist will watch you through a window. You will be able to talk to the technologist through a two-way intercom.

A CT scan usually takes 30 to 60 minutes but could take up to 2 hours.

CT scan with contrast (CT myelogram)

A standard CT scan may be done before the dye (contrast material) for a CT myelogram is given. The dye is usually put in the intrathecal space around your spinal cord. A sample of the fluid from the spinal canal (cerebrospinal fluid) may be taken out to look at under a microscope before the dye is put in.

If dye is placed in your back, you will lie on your stomach or on your side on a table in a fluoroscopy room. The dye is usually put in your lower back but may be put in at the base of your skull. The skin over the site may be shaved. It will be cleaned with a special soap. The area around the site may be numbed with medicine.

The table may be tilted or you may be moved into different positions so the dye moves to different areas of the spine.

You need to lie very still so the dye stays in the right place for clear pictures. Your pulse, breathing rate, and blood pressure may be checked during the test.

In some cases, the dye can also be put in a vein (IV) in your arm.

A CT scan with contrast material may take up to 2 hours. Drink lots of liquids for 24 hours after the scan to help flush the dye out of your body.

You will not have pain during the scan. The table you lie on may feel hard and the room may be cool. It may be hard to lie still during the test.

Some people feel nervous inside the CT scanner.

If a medicine to help you relax (sedative) or a dye (contrast material) is used, an IV is usually put in your hand or arm. You may feel a quick sting or pinch when the IV is started. The dye may make you feel warm and flushed and give you a metallic taste in your mouth. Some people feel sick to their stomach or get a headache. Tell the technologist or your doctor how you are feeling.

CT scan with contrast (CT myelogram)

If you have dye put in your back, you may feel a sting or pinch when the needle is put in.

After a test in which the dye is put in your back, you will be told to keep your head up and to not bend over or lie flat. This will help prevent headaches and seizures.

The chance of a CT scan causing a problem is small.

• There is a chance of an allergic reaction to the dye (contrast material).
• If you have diabetes or take metformin (Glucophage), the dye may cause problems. Your doctor will tell you when to stop taking metformin and when to start taking it again after the test so you will not have problems.
• You may have nausea or vomiting after the test.
• There is a small chance of an infection at the needle site on your spine or bleeding into the space around the spinal cord.
• Intrathecal injections may cause a headache. On rare occasions, seizures may occur after an injection of intrathecal contrast material.
• There is a slight chance of developing cancer from having tests that use radiation. The chance is higher in children or people who have many radiation tests. If you are concerned about this risk, talk to your doctor about the amount of radiation this test may give you or your child and confirm the test is needed.

After the test

Call 911 or other emergency services immediately if you have a seizure.

Call your doctor immediately if you:

• Have pain, weakness, or numbness in your legs.
• Have a severe headache.
• Have a headache that lasts more than 24 hours.
• Feel extremely irritable.
• Have problems urinating or having a bowel movement.
• Develop a fever.

A computed tomography (CT) scan uses X-rays to make detailed pictures of the spine and vertebrae in the neck (cervical spine), upper back (thoracic spine), or lower back (lumbosacral spine).

The radiologist may discuss the CT scan with you right after the test. However, complete results usually are ready for your doctor in 1 to 2 days.

The following may stop you from having the test or may change the test results:

• Pregnancy. CT scans are not usually done during pregnancy.
• Barium and bismuth used for another test. These substances show up on a CT scan. If a CT scan of the lower back is needed, it should be done before any tests that use barium, such as a barium enema.
• Metal objects in the body. These items, such as surgical clips or metal in joint replacements, may prevent a clear view of the body area.
• You are not able to lie still during the test.

• Sometimes your CT test results may be different than those from other types of X-ray tests, magnetic resonance imaging (MRI), or ultrasound scans because the CT scan provides a different view.
• CT results are often compared to positron emission tomography (PET) results to help find cancer. Some new scanners do both scans at the same time.
• MRI may give more information than a CT scan about the spinal discs and spinal cord. For more information, see the medical test Magnetic Resonance Imaging (MRI).
• When a CT scan of the spine is done with a myelogram, it is called a CT myelogram. An MRI of the spine is often done in place of a CT myelogram. For more information, see the medical test Myelogram.

Other Works Consulted

• Fischbach FT, Dunning MB III, eds. (2004). Manual of Laboratory and Diagnostic Tests, 7th ed. Philadelphia: Lippincott Williams and Wilkins.

• Pagana KD, Pagana TJ (2006). Mosby’s Manual of Diagnostic and Laboratory Tests, 3rd ed. St. Louis: Mosby.