Skeletal CT Scan
In this test,
a body scanner delivers x-rays to selected bones or jointssuch
as the shoulder, spine, hip, or pelvisat many different
angles. A computer compiles this information to construct highly
detailed, cross-sectional images, which are then displayed on
a TV monitor and recorded on x-ray film. In some cases, a contrast
dye may be injected to enhance detail of the bones and the soft
tissue inside and around the bones on the images.
A variation of this test, called
myelography, involves injection of a contrast dye directly into
the spinal canal to provide fine detail of the spine, spinal
cord, and surrounding tissues.
Purpose of the Test
abnormalities in the upper and lower spine, such as herniated
discs and spinal stenosis (a narrowing of the spinal canal),
that may be causing back pain and/or referred pain to the lower
To detect and
assess the extent of primary or metastatic bone tumors, and tumors
in the soft tissue surrounding bones.
joint abnormalities, such as fractures through the joint surface
and certain tumors, that are difficult to detect with other methods.
the location of an abscess.
skeletal changes in osteoporosis and other metabolic bone diseases.
Who Performs It
should not undergo this test because exposure to ionizing radiation
may harm the fetus.
allergies to iodine or shellfish may experience an allergic reaction
to iodine-based contrast dyes.
may be administered to people with significant bone or joint
pain if remaining still during the exam is likely to cause discomfort.
experience claustrophobia may find it difficult to undergo a
CT scan, which takes place in a narrow, tunnel-like structure.
This test may
not be possible for severely overweight individuals (over 300
Before the Test
doctor if you have an allergy to iodine or shellfish. You may
be given a combined antihistamine-steroid preparation to reduce
the risk of an allergic reaction to the contrast dye.
Tell your doctor
if you suffer from claustrophobia. He or she may prescribe a
sedative to help you tolerate the procedure.
If a contrast
dye is to be used or if sedation is anticipated, you will be
instructed to fast for 4 hours before the test.
You will be
asked to remove your clothes, jewelry, and any metal objects
and put on a hospital gown.
What You Experience
You will lie
on your back on a narrow table that is then advanced into the
which encircles you, rotates around you taking pictures at different
intervals and from various angles. You will feel the table move
during the test.
You must remain
as still as possible because any movement can distort the images
on the scan.
may advise you on how to control your breathing at several points
during the procedure.
dye may be administered through an intravenous (IV) needle or
catheter inserted in a vein in your arm. You may feel a brief
warm, flushing sensation after the injection; rarely, some people
experience nausea and possibly vomiting.
The test typically
takes 30 to 60 minutes.
Risks and Complications
involves exposure to low levels of radiation.
may experience an allergic reaction to the iodine-based contrast
dye, which can cause symptoms such as nausea, sneezing, vomiting,
hives, and occasionally a life-threatening response called anaphylactic
shock. Emergency medications and equipment are kept readily available.
After the Test
You are free
to resume your normal diet and activities.
If a contrast
dye was used, you are encouraged to drink clear fluids to avoid
dehydration and help flush the material out of your system.
Blood may collect
and clot under the skin (hematoma) at the dye injection site;
this is harmless and will resolve on its own. For a large hematoma
that causes swelling and discomfort, apply ice initially; after
24 hours, use warm, moist compresses to help dissolve the clotted
reactions to the contrast dye, such as hives, rash, or itching,
may appear 2 to 6 hours after the procedure. If this occurs,
your doctor will prescribe antihistamines or steroids to ease
will examine the recorded images for evidence of abnormalities
in the bones or joints being examined.
If a definitive
diagnosis can be made, appropriate treatment will be initiated,
depending on the specific problem.
In some cases,
additional tests may be needed to establish a diagnosis and determine
the extent of the problem. For example, magnetic resonance imaging
may provide better detail of the soft tissues near the spine.
From The Johns Hopkins Consumer Guide to Medical
Tests. You can order this book now on
our secure server.