A chemical called contrast may be used to help improve the images. Some people can have an allergic reaction or develop
with contrast material.
However, these reactions are rare. Your doctor will review a list of possible complications of a CT scan with contrast.
A CT scan does use radiation. You and your doctor will weigh the harms and benefits of this test. A CT scan may not be advised if you are pregnant.
Be sure to discuss these risks with your doctor before the test.
What to Expect
Prior to Test
Your doctor may ask you to:
Avoid eating or drinking anything for 4 hours before the test if contrast will be used.
Remove any metal objects, such as jewelry, hearing aids, or dentures.
Description of the Test
If contrast is needed, it will be injected into a vein.
You will be positioned on a special moving table. The table will move slowly through the CT scanner. You will need to stay still during the entire test. The technician may need to use a device to keep your head still. As the scanner takes pictures, you will hear humming and clicking. You will be able to talk to the technician through an intercom.
If you had contrast, you may be asked to drink extra fluid. This will flush the contrast from your body.
How Long Will It Take?
About 10 minutes
Will It Hurt?
You may feel flushed if you are given contrast. You may also notice a salty or metallic taste in your mouth and feel nauseated.
The CT images will be sent to a radiologist for analysis. Your doctor will receive the results and discuss them with you.
Call Your Doctor
If you were given contrast, call your doctor if any of the following occur after the test:
Brenner DJ. Should we be concerned about the rapid increase in CT usage? Rev Environ Health. 2010;25(1):63-68.
Computed tomography (CT)—Head. Radiology Info.org—Radiological Society of North America website. Available at: http://www.radiologyinfo.org/en/info.cfm?pg=headct. Updated June 8, 2016. Accessed February 15, 2018.
Positron emission tomography—computed tomograpy (PET/CT). Radiology Info.org—Radiological Society of North America website. Available at: http://www.radiologyinfo.org/en/info.cfm?pg=PET. Updated January 23, 2017. Accessed February 15, 2018.
Last reviewed March 2018 by
EBSCO Medical Review Board
Rimas Lukas, MD
Last Updated: 6/24/2013
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