CT Scan (General)
(Computed Tomography Scan; Computed Axial Tomography; CAT Scan)
A CT scan uses x-ray technology to take views of the inside of the body. It can take clearer and more detailed pictures than
|CT Scan of the Head
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Reasons for test
CT scans are used to:
- Look for bleeding inside the body, especially in the skull
- Study the chest and belly
- Figure out the size and site of a tumor
- Diagnose skeletal problems
- Diagnose blood vessel diseases
- Plan radiation treatments for cancer
and other tests
- Plan surgery
- Identify injuries from trauma
Problems are rare, but all procedures have some risk. Your doctor will go over problems that may happen, such as:
- Allergic reaction to contrast material
- Damage to the kidney from contrast material
If you are given a contrast dye, you may have an increased risk of problems if you also have:
- Kidney problems
You are exposed to some radiation during a CT scan. It can raise your lifetime risk of cancer. This risk raises the more times you are exposed. Pregnant woman and children are at higher risk. CT scans are usually not advised for pregnant women.
Talk to your doctor about these risks before the test.
What to Expect
Prior to Test
Before the test, your doctor will likely ask about:
- Medicines you take
- Whether you are pregnant or trying to get pregnant
- Before your test, follow your doctor’s advice about any changes to your medicines or food.
At the healthcare facility:
- Staff will tell you about the test and answer any questions you may have.
- You will remove your clothes and put on a gown or robe.
- You will remove all jewelry, hair clips, dentures, and other objects. These items can make the images hard to read.
- If your CT scan uses oral contrast material, you will need to drink it at this time.
Description of the Test
You will lie (usually on your back) on a mobile bed. The bed will slide into the donut-shaped CT scanner. An IV line may be placed in your hand or arm. Salt water and contrast material may be injected into the IV during the test. The technologist will leave the room. Staff will talk to you using an intercom. The machine will take a series of pictures of the part of your body that is being studied. Your bed may move slightly between pictures.
You will need to wait for the technician to review your images. More images may need to be taken.
How Long Will It Take?
About 10-15 minutes. It will take longer if more pictures need to be taken.
Will It Hurt?
You may feel warm and flushed if contrast material is injected into your vein.
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:
Symptoms of allergic reaction, such as
, itching, nausea, swollen or itchy eyes, tight throat, or problems breathing
- Any other problems
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:
Updated March 16, 2016. Accessed March 13, 2018.
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. Updated March 7, 2018. Accessed March 13, 2018.
EBSCO Medical Review Board
Marcie L. Sidman, MD
- Review Date:
- Update Date: