What Is a Chest CT Scan?
A chest computed tomography (to-MOG-ra-fee), or CT,
scan is a painless, noninvasive test. It creates precise images of the
structures in your chest, such as your lungs. “Noninvasive” means
that no surgery is done and no instruments are inserted into your body.
A chest CT scan is a type of x ray. However, a CT
scan’s pictures show more details than pictures from a standard
chest x ray.
Like other x-ray tests, chest CT scans use a form of
energy called ionizing radiation. This energy helps create pictures of the
inside of your chest.
Overview
Doctors use chest CT scans to:
- Show the size, shape, and position of your lungs
and other structures in your chest.
- Follow up on abnormalities that are found on
standard chest x rays.
- Find the cause of lung symptoms, such as
shortness of breath or chest pain.
- See whether you have a lung problem, such as a
tumor, excess fluid around the lungs, or a
pulmonary
embolism (PULL-mun-ary EM-bo-lizm; a blood clot in the lungs). The test
also is used to check for other conditions, such as tuberculosis
(tu-ber-kyu-LO-sis), emphysema (em-fi-SE-ma), and
pneumonia.
The chest CT scanning machine takes many pictures,
called slices, of the lungs and the inside of the chest. A computer processes
these pictures; they can be viewed on a monitor or printed on film. The
computer also can stack the pictures to create a very detailed,
three-dimensional (3D) model of organs.
Sometimes, a special substance (called contrast dye)
is injected into a vein in your arm. This substance highlights areas in your
chest, which helps create clearer images.
Outlook
Chest CT scans have few risks. Because the test uses
radiation, there may be a slight risk of cancer.
Children are more sensitive to radiation than adults
because they’re smaller and still growing.
The amount of radiation will vary with the type of
CT scan. On average, though, the radiation will not exceed the amount a person
is naturally exposed to over 3 years. The benefits of a CT scan should always
be weighed against the possible risks.
Rarely, people have allergic reactions to the
contrast dye that’s sometimes used for chest CT scans. If this happens,
your doctor will give you medicine to relieve the symptoms.
Types of Chest CT Scans
A CT scanner is a large machine with a tunnel-like
hole in the center. During a chest CT scan, you lie on a table as it moves
small distances at a time through the hole.
An x-ray beam rotates around your body as you move
through the hole. A computer takes data from the x rays and creates a series of
pictures, called slices, of the inside of your chest.
Different types of chest CT scans have different
diagnostic uses.
High-Resolution Chest CT Scan
High-resolution CT (HRCT) scans provide more than
one slice in a single rotation of the x-ray tube. Each slice is very thin and
provides a lot of details about the organs and other structures in your chest.
Spiral Chest CT Scan
For this scan, the table moves continuously through
the tunnel-like hole as the x-ray tube rotates around you. This allows the
x-ray beam to follow a spiral path.
The machine’s computer can process the many
slices into a very detailed, three-dimensional (3D) picture of the lungs and
other structures in the chest.
Other Names for Chest CT Scans
- Lung imaging test
- Computed axial tomography (CAT) scan
- Helical CT scan (another name for spiral CT scan)
Who Needs a Chest CT Scan?
People who have symptoms of lung problems, such as
chest pain or trouble breathing, may need chest CT scans. The scan helps find
the cause of the symptoms.
Chest CT scans look for problems such as tumors,
excess fluid around the lungs, and
pulmonary
embolism (a blood clot in the lungs). The scan also checks for other
conditions, such as tuberculosis, emphysema, and
pneumonia.
Your doctor may order a chest CT scan if a standard
chest
x ray doesn’t help diagnose the problem. For example, your doctor
might order a chest CT scan after a chest x ray to:
- See more detailed pictures of your lungs and
other structures in your chest
- Find the exact location of a tumor or other
problem
- Show something that isn’t visible on a
chest x ray
What To Expect Before a Chest CT Scan
What To Wear
Wear loose-fitting, comfortable clothing for the
test. In some cases, the CT scan technician (a person specially trained to do
CT scans) may ask you to wear a hospital gown.
You also may want to avoid wearing jewelry and other
metal objects. You’ll be asked to take off any jewelry, eyeglasses, and
metal objects that might interfere with the test.
You may be asked to remove hearing aids and dentures
as well. Let the technician know if you have any body piercing on your chest.
Pregnancy and Other Conditions
Tell your doctor whether you’re pregnant or
may be pregnant. If possible, you should avoid unnecessary radiation exposure
during pregnancy. This is because of the concern that radiation may harm the
fetus.
You and your doctor will decide whether the benefits
of a chest CT scan outweigh the possible risks to the fetus, or whether another
test might be better. If you do have the chest CT scan, the technician will
take extra steps to reduce the fetus’ exposure to radiation.
You also should tell your doctor whether:
- You’re taking any medicines
- You have any allergies
- You’ve recently been ill
- You have any medical conditions (for example,
heart disease,
asthma,
diabetes, kidney disease, or thyroid problems)
These factors or conditions may raise your risk for
a bad reaction to the test.
The CT Machine
The CT scanner is a large machine with a tunnel-like
hole in the center. You lie on a table that goes through the hole.
Tell your doctor if you’re afraid of tight or
closed spaces. He or she may give you medicine to help you relax. This medicine
may make you sleepy, so you’ll need to arrange for a ride home after the
test.
Contrast Dye
Your doctor may give you a special substance (called
contrast dye). This substance highlights areas of your chest and helps create
clearer images.
The contrast dye will be injected into a vein in
your arm. You may feel some discomfort when the needle is inserted. As the
substance is injected, you also may feel warm and have a metallic taste in your
mouth. These feelings last only a few minutes.
Your doctor may ask you not to eat or drink for a
few hours before the test, especially if contrast dye is part of the test.
Some people are allergic to the contrast dye. If you
have allergic symptoms, such as itching or hives, tell the technician or doctor
right away. He or she can give you medicine to relieve the symptoms.
The most common type of contrast dye used in lung CT
scans contains iodine. Let your doctor know if you’re allergic to iodine.
If you’re breast-feeding, ask your doctor how
long you should wait after the test before you breast-feed. The contrast dye
can be passed to your baby through your breast milk.
You may want to prepare for the test by pumping and
saving milk for 24 to 48 hours in advance. You can bottle-feed your baby in the
hours after the CT scan.
What To Expect During a Chest CT Scan
A chest CT scan takes about 30 minutes, which
includes preparation time. The actual scanning time is much shorter, only a few
minutes or less.
The CT scanner is a large machine that has a
tunnel-like hole in the middle. You will lie on a narrow table that moves
through the hole.
While you’re inside the scanner, an x-ray tube
moves around your body. You will hear soft buzzing, clicking, or whirring
noises as the scanner takes pictures.
The CT scan technician who controls the machine will
be in the next room. He or she can see you through a glass window and talk to
you through a speaker.
Moving your body can cause the pictures to blur. The
technician will ask you to lie still and hold your breath for short periods.
These measures help make the pictures as clear as possible.
The scan itself doesn’t hurt, but you may feel
anxious if you get nervous in tight or closed spaces. Your doctor may give you
medicine to help you relax.
What To Expect After a Chest CT Scan
You usually can return to your normal routine right
after a chest CT scan.
If you got medicine to help you relax during the CT
scan, your doctor will tell you when you can return to your normal routine. The
medicine may make you sleepy, so you’ll need someone to drive you home.
If contrast dye was used during the test, you may
have a bruise where the needle was inserted. Your doctor may give you special
instructions, such as drinking plenty of liquids to flush out the contrast dye.
If you’re breast-feeding, ask your doctor how
long you should wait after the test before you breast-feed. The contrast dye
can be passed to your baby through your breast milk.
You may want to prepare for the test by pumping and
saving milk for 24 to 48 hours in advance. You can bottle-feed your baby in the
hours after the CT scan.
What Does a Chest CT Scan Show?
A chest CT scan provides detailed pictures of the
size, shape, and position of your lungs and other structures in your chest.
Doctors use this test to:
- Follow up on abnormalities that are found on
standard
chest
x rays.
- Find the cause of lung symptoms, such as
shortness of breath or chest pain.
- See whether you have a lung problem, such as a
tumor, excess fluid around the lungs, or a
pulmonary
embolism (a blood clot in the lungs). The test also is used to check for
other conditions, such as tuberculosis, emphysema, and
pneumonia.
What Are the Risks of a Chest CT Scan?
Radiation
You will receive radiation during a chest CT scan.
The amount will vary with the type of CT scan. On average, though, the amount
of radiation will not exceed the amount you’re naturally exposed to over
3 years. The radiation from the test is gone from the body within a few days.
Children are more sensitive to radiation because
they’re smaller than adults and still growing.
Exposure to radiation is associated with a risk of
cancer. However, it’s not known whether the amount of radiation from a
chest CT scan puts you at higher risk than the amount of radiation you’re
naturally exposed to.
You and your doctor will decide whether the benefits
of the CT scan outweigh any possible risks. Your doctor also will try to avoid
ordering repeated CT scans over a short period.
Allergic Reaction
The contrast dye used in some chest CT scans can
cause an allergic reaction, such as hives or trouble breathing. The risk of
this happening is slight. If you do have an allergic reaction, your doctor can
give you medicine to relieve it.
The most common contrast dye used in CT scans
contains iodine. Tell your doctor if you’re allergic to iodine.
Key Points
- A chest CT scan is a painless, noninvasive test
that creates precise images of the structures in your chest, such as your
lungs.
- A chest CT scan is a type of x ray, but a CT
scan’s pictures show more details than the pictures from a standard
chest
x ray. Like other x-ray tests, chest CT scans use a form of energy called
ionizing radiation. This energy helps create pictures of the inside of your
chest.
- A CT scanner is a large machine with a
tunnel-like hole in the center. During a chest CT scan, you lie on a table as
it moves small distances at a time through the hole.
- The chest CT scanning machine takes many
pictures, called slices, of the lungs and the inside of the chest. Sometimes, a
special substance (called contrast dye) is injected into a vein in your arm.
This substance highlights areas in your chest, which helps create clearer
images.
- People who have symptoms of lung problems, such
as a chest pain or trouble breathing, may need chest CT scans.
- The scan helps find the cause of the symptoms. It
looks for problems such as tumors, excess fluid around the lungs, and
pulmonary
embolism (a blood clot in the lungs). The scan also can check for other
conditions, such as tuberculosis, emphysema, and
pneumonia.
- Wear loose-fitting, comfortable clothing for the
chest CT scan. You’ll be asked to remove jewelry, eyeglasses, and metal
objects that might interfere with the test. Let your doctor know if
you’re pregnant, have other medical conditions are taking any medicines,
or have any allergies.
- Contrast dye may be used as part of the chest CT
scan. If you’re breast-feeding, ask your doctor how long you should wait
after the test before you breast-feed. The contrast dye can be passed to your
baby through your milk. You may want to prepare for the scan by pumping and
saving milk for 24 to 48 hours in advance. You can bottle-feed your baby in the
hours after the scan.
- A chest CT scan takes about 30 minutes, which
includes preparation time. The scan itself doesn’t hurt, but you may feel
anxious if you get nervous in tight or closed spaces. Your doctor may give you
medicine to help you relax.
- You usually can return to your normal routine
right after a chest CT scan. If contrast dye was used, your doctor may give you
special instructions, such as drinking plenty of liquids to flush out the
substance.
- A chest CT scan provides detailed pictures of
the size, shape, and position of your lungs and other structures in your chest.
A CT scan can show whether you have a lung problem or other condition.
- Chest CT scans have few risks. Because the test
uses radiation, there may be a slight risk of cancer. However, the amount used
is about the same as the amount you’re naturally exposed to over 3 years.
Rarely, people have allergic reactions to the contrast dye that sometimes used.
If this happens, your doctor will give you medicine to relieve the symptoms.
Links to Other Information About Chest CT
Scans
Non-NHLBI Resources
Clinical Trials
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