Test Overview
A CT scan uses
X-rays to make detailed pictures of the
spine and vertebrae.
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 called contrast material may be put in a vein (IV) in your arm or into the spinal canal. The dye makes structures and organs easier to see on the CT
pictures. The dye may be used to check blood flow and look for
tumors, areas of
inflammation, or nerve damage.
See
CT images of the cervical spine.
Why It Is Done
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.
How To Prepare
Before the CT scan, tell your doctor
if you:
- Are or might be pregnant.
- Are allergic to any medicines, including iodine
dyes.
- Have a heart condition, such as
heart failure.
- Have
diabetes or take metformin (Glucophage) for your
diabetes. You may have to adjust your medicine for a day before and
after the test.
- Have had kidney
problems.
- Have
asthma.
- Have had
multiple myeloma.
- Have had an X-ray test using barium
contrast material (such as a
barium enema) or have taken a 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 sedative to help you relax.
Arrange for someone to take you home in case you get a
sedative for the test.
Talk to your
doctor 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?).
How It Is Done
A CT scan is usually done by a
radiology technologist. The pictures are usually read
by a
doctor (radiologist). Other doctors also may review a CT scan.
You
may need to take off any jewelry. You will need to take off all or most of your
clothes, depending on which area is studied. You may be able to wear your
underwear for some scans. 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.
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. But the technologist will watch you through a window. You
will be able to talk to the technologist through a two-way intercom.
The test will take about 30 to 60 minutes. Most of this time is spent getting ready for the scan. The actual scan only takes a few seconds.
CT scan with contrast (CT myelogram)
A standard CT
scan may be done before the contrast material for a CT
myelogram is given. The dye is usually put in the space around your spinal cord. A sample of
the fluid from the spinal canal (cerebrospinal fluid) may be taken out
so other tests can be done on it.
If dye is
placed in your back, you will lie on your stomach or on your side on a table. 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. 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
usually takes 15 to 30 minutes. Drink lots of liquids for
24 hours after the scan to help flush the dye out of your body.
How It Feels
The test will not cause pain.
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 you get medicine to help you relax or if contrast material is used, you may have an IV 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.
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.
Risks
The chance of a CT scan causing a problem is
small.
- There is a chance of an
allergic reaction to the 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.
- An injection into the space around the spinal cord may
cause a headache. Rarely, seizures may occur after an injection of contrast material.
- There is a small chance of developing
cancer from having some types of CT
scans.1 The chance is
higher in children, young adults, and 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
that the test is needed.
Results
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).
Complete
results usually are ready for your doctor in 1 to 2 days.
CT scan of the spine
| Normal: |
Spinal bones (vertebrae) are
normal in shape, number, and alignment.
|
|
The discs and joints that support the spine
are normal.
|
|
The spinal canal is normal in size and
shape.
|
|
If
contrast material is used, it flows evenly through the
spinal canal. No narrowing or blockage of the spinal canal is
present.
|
|
None of the nerves leaving the spinal cord
are compressed or pinched. No growths or bulges are present.
|
| Abnormal: |
Spinal bones (vertebrae) are missing,
damaged, or out of alignment.
|
|
One or more discs may be damaged. One or
more
herniated discs are found.
|
|
The flow of contrast material through the
spinal canal is restricted or blocked, indicating narrowing of the canal (spinal stenosis).
|
|
The vertebrae show signs of
arthritis or bone problems caused by
osteoporosis.
|
|
A condition that has been present from
birth (congenital condition) is present in the spine or the vertebrae.
|
|
An
abscess or
spinal tumor is found.
|
What Affects the Test
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.
What To Think About
- 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.
- Children who need a CT scan may need special
instructions for the test. If the child is too young to hold still or is
afraid, the doctor may give the child a medicine (sedative) to
help him or her relax.
- If your child is scheduled for a CT scan,
talk with your child's doctor about the need for the scan and the risk of
radiation exposure to your child.
- 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 topic
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
topic
Myelogram.
References
Citations
-
Einstein AJ, et al. (2007). Estimating risk of cancer
associated with radiation exposure from 64-slice computed tomography coronary
angiography. JAMA, 298(3): 317–323.
Other Works Consulted
- Fischbach FT, Dunning MB III, eds. (2009).
Manual of Laboratory and Diagnostic Tests, 8th ed.
Philadelphia: Lippincott Williams and Wilkins.
- Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby.
-
U.S. Food and Drug Administration (2008).
FDA preliminary public health notification: Possible malfunction of electronic
medical devices caused by computed tomography (CT) scanning. Available online:
http://www.fda.gov/cdrh/safety/071408-ctscanning.html.
Credits
|
By
|
Healthwise Staff |
|
Primary Medical Reviewer
|
Adam Husney, MD - Family Medicine |
|
Specialist Medical Reviewer
|
Howard Schaff, MD - Diagnostic Radiology |
|
Last Revised
|
September 21, 2012 |