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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
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,
adrenal glands, lungs, and heart. It also can study
blood vessels, bones, and the spinal cord.
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.
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
For people with cancer, a CT
scan can help determine how much the cancer has spread. This is called staging
Before the CT scan, tell your doctor
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?).
A CT scan is usually done by a
radiology technologist. The pictures are usually read
radiologist, who writes the report. Other doctors also may review a CT scan.
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
During the test, you will lie on a table that is attached to
the CT scanner.
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
scan 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
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
A computed tomography (CT) scan uses
X-rays to make detailed pictures of structures inside the body.
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
No bleeding or collections of fluid are
An organ is too large or too small,
damaged, or infected.
abscesses are present.
Foreign objects (such as metal or glass
fragments) are present.
gallstones are present.
Growths (such as tumors) are seen in the
adrenal gland, or
A CT scan of the chest shows a
pulmonary embolism, fluid in the lungs, or
aneurysm is present.
Blockage is found in the intestines or in
A CT of the belly shows
inflammatory bowel disease or
Lymph nodes are
One or more blood vessels are
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 the Young. Circulation, 118: 586–606.
Detterbeck FC, et al. (2013). Screening for lung cancer. Diagnosis and management of lung cancer, 3rd ed. American College of Chest Physicians evidence-based clinical practice guidelines. Chest, 143(5, Suppl): e78S–e92S.
Fischbach FT, Dunning MB III, eds. (2009).
Manual of Laboratory and Diagnostic Tests, 8th ed.
Philadelphia: Lippincott Williams and Wilkins.
National Comprehensive Cancer Network (2010). Non–Small Cell Lung Cancer,
version 2.2010. Available online:
Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby.
Pearce MS, et al. (2012). Radiation exposure from CT scans in childhood and subsequent risk of leukaemia and brain tumours: A retrospective cohort study. Lancet, 380(9840): 499–505.
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:
ByHealthwise StaffPrimary Medical ReviewerAdam Husney, MD - Family MedicineE. Gregory Thompson, MD - Internal MedicineSpecialist Medical ReviewerHoward Schaff, MD - Diagnostic Radiology
Current as ofSeptember 9, 2014
Current as of:
September 9, 2014
Adam Husney, MD - Family Medicine & E. Gregory Thompson, MD - Internal Medicine & Howard Schaff, MD - Diagnostic Radiology
How this information was developed to help you make better health decisions.
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