CT Scan (General)
(Computed Tomography Scan; Computed Axial Tomography; CAT Scan)
by Krisha McCoy, MS
A CT scan is a machine that takes a series of x-rays to make a picture with many details. It can take images of bone, blood vessels, and soft tissue at different angles. It makes more detailed pictures than regular x-rays.
Reasons for test
CT scans can help to:
There is some radiation exposure during a CT scan. It is very low but higher than radiation from regular x-rays. This level of radiation has not been shown to cause long-term harm. Talk to your doctor about the risks and benefits of CT scan for you.
Tell the care team if you are pregnant or may be pregnant. A CT scan will probably not harm an unborn child but there may be safer choices.
A special dye called contrast material may be used. It helps to make a clearer picture of one area. The dye can cause an allergic reaction, but it is rare. Allergic reaction can range from mild rash or itching to serious, life-threatening event. Tell your doctor if you have had an allergic reaction to dye or any severe allergic reaction.
Talk to your doctor about these risks before the test.
What to Expect
Prior to Test
You may be asked to:
You may be given a contrast dye. It may be given through:
Description of the Test
CT scanners are shaped like a large doughnut standing on its side. You lie on a narrow, table that slides through the opening into a tunnel. Straps and pillows may be used to help you stay in position. During a head scan, the table may be fitted with a special cradle that holds your head still.
The table slides into the scanner while detectors and the X-ray tube rotate around you. Each rotation makes several images of your body. You may hear buzzing and whirring noises.
A tech in a separate room can see and hear you. You will be able to talk to them throughout the test. You may need to hold your breath at some points to prevent blurred images.
You may be asked to wait for a short time right after the exam. You can return to your normal routine once you leave.
How Long Will It Take?
About 10 to 15 minutes for the scan. New machines may take less time. You may be at the site for about 30 minutes all together.
Will It Hurt?
You may feel warm and flushed if a contrast material is injected. It should pass within a few minutes. The enema contrast can cause some bloating in the belly.
The CT images will be sent to a radiologist who will study them. Your doctor will get the results and talk about them with you.
Call Your Doctor
Call your doctor if you have:
If you think you have an emergency, call for emergency medical services right away.
NIH Clinical Center
Radiology Info—Radiological Society of North America
Canadian Association of Radiologists
Canadian Radiation Protection Association
Computed tomography (CT)—body. Radiology Info—Radiological Society of North America website. Available at:
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Accessed January 26, 2021.
Radiation-emitting products: computed tomography (CT). US Food & Drug Administration website. Available at: https://www.fda.gov/Radiation-EmittingProducts/RadiationEmittingProductsandProcedures/MedicalImaging/MedicalX-Rays/ucm115317.htm. Accessed January 26, 2021.
Last reviewed Janaury 2021 by EBSCO Medical Review BoardNicole S. Meregian, PA
Last Updated: 1/26/2021
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