A computed tomography (CT) scan uses X-rays to make detailed pictures of structures inside of the body.
During the test, you will lie on a table that is attached to the CT scanner, which is a large doughnut-shaped machine. The CT scanner sends X-rays through the body area being studied. Each rotation of the scanner provides a picture of a thin slice of the organ or area. All of the pictures are saved as a group on a computer. They also can be printed.
In some cases, a dye called contrast material may be used. It may be put in a vein (IV) in your arm, or it may be placed into other parts of your body (such as the rectum or a joint) to see those areas better. For some types of CT scans you drink the dye. The dye makes structures and organs easier to see on the CT pictures.
A CT scan can be used to study all parts of your body, such as the chest, belly, pelvis, or an arm or leg. It can take pictures of body organs, such as the liver, pancreas, intestines, kidneys, bladder, adrenal glands, lungs, and heart. It also can study blood vessels, bones, and the spinal cord.
Fluoroscopy CT is a special test that is not widely available. It uses a steady beam of X-rays to look at movement within the body. It allows the doctor to see your organs move or to guide a biopsy needle or other instrument into the right place inside your body.
CT scans are used to study areas of the body and the arms or legs.
A CT scan may be used to make sure a procedure is done correctly. For example, the doctor may use CT to guide a needle during a tissue biopsy or to guide the proper placement of a needle to drain an abscess.
For people with cancer, a CT scan can help determine how much the cancer has spread. This is called staging the cancer.
Before the CT scan, tell your doctor if you:
Arrange for someone to take you home in case you get a medicine to help you relax (sedative) for the test.
If you have a CT scan of your belly, you may be asked to not eat any solid foods starting the night before your scan. For a CT scan of the belly, you may drink contrast material. For some CT scans, you may need a laxative or an enema before the test.
Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form (What is a PDF document?).
You may need to take off any jewelry. You will need to take off all or most of your clothes, depending on which area is studied. You may be able to wear your underwear for some scans. You will be given a gown to use during the test.
During the test, you will lie on a table that is attached to the CT scanner.
The table slides into the round opening of the scanner, and the scanner moves around your body. The table will move while the scanner takes pictures. You may hear a click or buzz as the table and scanner move. It is very important to lie still during the test.
During the test, you may be alone in the scanning room. But the technologist will watch you through a window. You will be able to talk to the technologist through a two-way intercom.
The test will take about 30 to 60 minutes. Most of this time is spent getting ready for the scan. The actual scan only takes a few seconds.
The test will not cause pain. The table you lie on may feel hard, and the room may be cool. It may be hard to lie still during the test.
Some people feel nervous inside the CT scanner.
If a medicine to help you relax (sedative) or dye (contrast material) is used, an IV is usually put in your hand or arm. You may feel a quick sting or pinch when the IV is started. The dye may make you feel warm and flushed and give you a metallic taste in your mouth. Some people feel sick to their stomachs or get a headache. Tell the technologist or your doctor how you are feeling.
The chance of a CT scan causing a problem is small.
Complete results usually are ready for your doctor in 1 to 2 days.
The organs and blood vessels are normal in size, shape, and location. No blood vessels are blocked.
No foreign objects (such as metal or glass fragments), growths (such as cancer), inflammation, or infection are present.
No bleeding or collections of fluid are present.
Foreign objects (such as metal or glass fragments) are present.
A CT scan of the chest shows a pulmonary embolism, fluid in the lungs, or infection.
An aneurysm is present.
Blockage is found in the intestines or in the bile ducts.
Lymph nodes are enlarged.
One or more blood vessels are blocked.
A growth, fracture, infection, or other problem is found in an arm or leg.
The following may stop you from having the test or may change the test results:
- Einstein AJ, et al. (2007). Estimating risk of cancer associated with radiation exposure from 64-slice computed tomography coronary angiography. JAMA, 298(3): 317–323.
Other Works Consulted
- Bluemke, D, et al. (2008). Noninvasive coronary artery imaging: Magnetic resonance angiography and multidetector computed tomography angiography. A scientific statement From the American Heart Association Committee on Cardiovascular Imaging and Intervention of the Council on Cardiovascular Radiology and Intervention, and the Councils on Clinical Cardiology and Cardiovascular Disease in t
- Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
- Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby.
- U.S. Food and Drug Administration (2008). FDA preliminary public health notification: Possible malfunction of electronic medical devices caused by computed tomography (CT) scanning. Available online: http://www.fda.gov/cdrh/safety/071408-ctscanning.html.
|Primary Medical Reviewer||Adam Husney, MD - Family Medicine|
|Specialist Medical Reviewer||Howard Schaff, MD - Diagnostic Radiology|
|Last Revised||September 21, 2012|
Last Revised: September 21, 2012
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