Brain CT Scan
(Computed Tomography of the Brain, Intracranial
body scanner delivers x-rays to the head at many different angles.
A computer then compiles this information to construct highly
detailed, cross-sectional images of the brain. In some cases,
a contrast dye may be injected to better define tissues and blood
vessels on the scans and enhance the images.
Purpose of the Test
To help diagnose
disorders affecting the brain, including tumors; infarction (an
area of dead tissue caused by interruption of blood flow); bleeding
within the brain; hematoma (collection of blood on the brain);
hydrocephalus (accumulation of fluid within the ventricles of the
the stage of brain tumors and to monitor them after treatment
Who Performs It
and/or a trained technician.
CT scans are
not usually done during pregnancy because exposure to ionizing
radiation may harm the fetus.
allergies to iodine or shellfish may experience an allergic reaction
to the iodine-based contrast dye.
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 and drink large
amounts of fluids on the day before the test to prevent dehydration.
If a dye is not being used, fasting is unnecessary.
the test, remove all jewelry and metal objects.
What You Experience
You are asked
to lie on your back on a narrow table. Your head is immobilized
in a brace (but your face is left uncovered) and then advanced
into the CT scanner.
takes pictures at different intervals and varying levels over
your head, so you will feel the table move during the test. The
resulting images are displayed on a viewing monitor and recorded
on x-ray film.
You must remain
still because any movement can distort the image on the scan.
dye may be administered through an intravenous (IV) needle or
catheter inserted into a vein in your arm. (Upon injection of
the dye, you may experience a mild nausea, flushing, warmth,
or a salty taste in the mouth.) The scanning process is then
The test usually
lasts 10 to 20 minutes. If a contrast dye is used, it may take
up to 40 minutes because scans are taken before and after the
dye is given.
Risks and Complications
exposure is minimal, you will receive a higher dose of radiation
than during standard x-ray procedures.
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.
are dehydrated or those with impaired kidney function may experience
acute renal failure from infusion of the contrast dye. Adequate
hydration before the test can reduce this risk.
After the Test
dye was used, you are encouraged to drink clear fluids to avoid
dehydration and help flush the dye out of your system.
You are free
to resume your normal diet and activities.
dye was injected, blood may collect and clot under the skin (hematoma)
at the 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 blood.
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 CT images for evidence of any abnormality.
If a definitive
diagnosis can be made based on the images, appropriate treatment
will be initiated, depending on the specific problem.
In some cases,
additional tests, such as an MRI or a PET scan of the brain,
may be needed to establish a diagnosis and determine the extent
of the problem.
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