Computed
Tomography (CT or CAT) Scan of the Chest
(Chest
CT Scan, Thoracic CT Scan, CT of the Thorax)
Computed
tomography (CT or CAT scan) is a diagnostic imaging
procedure that uses a combination of x-rays and
computer technology to produce cross-sectional
images (often called slices), both horizontally
and vertically, of the body. A CT scan shows detailed
images of any part of the body, including the
bones, muscles, fat, and organs. CT scans are
more detailed than standard x-rays. CT scans also
minimize exposure to radiation.
In standard
x-rays, a beam of energy is aimed at the body
part being studied. A plate behind the body part
captures the variations of the energy beam after
it passes through skin, bone, muscle, and other
tissue. While much information can be obtained
from a standard x-ray, a lot of detail about internal
organs and other structures is not available.
In computed
tomography, the x-ray beam moves in a circle around
the body. This allows many different views of
the same organ or structure. The x-ray information
is sent to a computer that interprets the x-ray
data and displays it in a two-dimensional (2D)
form on a monitor. While many images are taken
during a CT scan, in some cases the patient receives
the same or less radiation exposure than with
a single standard x-ray.
CT scans
may be done with or without “contrast.”
Contrast refers to a substance taken by mouth
or injected into an intravenous (IV) line that
causes the particular organ or tissue under study
to be seen more clearly. Contrast examinations
may require you to fast for a certain period of
time before the procedure. Your physician will
notify you of this prior to the procedure.
CT scans
of the chest can provide more detailed information
about organs and structures inside the chest than
standard x-rays of the chest, thus providing more
information related to injuries and/or diseases
of the chest (thoracic) organs.
CT scans
of the chest may also be used to visualize placement
of needles during biopsies of thoracic organs
or tumors, or during aspiration (withdrawal) of
fluid from the chest. CT scans of the chest are
useful in monitoring tumors and other conditions
of the chest before and after treatment.
Other
related procedures that may be used to assess
the heart include resting or exercise electrocardiogram
(ECG or EKG), Holter monitor, signal-averaged
ECG, cardiac catheterization, chest x-ray, echocardiogram,
electrophysiological studies, magnetic resonance
imaging (MRI) of the heart, myocardial perfusion
scans, radionuclide angiography, and ultrafast
CT scan. Please see these procedures for additional
information.
The
chest contains organs of the respiratory and cardiovascular
systems, as well as the esophagus (hollow tube
of muscle extending from below the tongue to the
stomach). A CT scan of the chest may be performed
to assess the chest and its organs for tumors
and other lesions, injuries, intra-thoracic bleeding,
infections, unexplained chest pain, obstructions,
or other conditions, particularly when another
type of examination, such as x-rays or physical
examination, is not conclusive.
A CT
scan of the chest may also be used to evaluate
the effects of treatment of thoracic tumors. Another
use of chest CT is to provide guidance for biopsies
and/or aspiration of tissue from the chest.
There
may be other reasons for your physician to recommend
a CT scan of the chest.
The
amount of radiation used during a CT scan is considered
minimal; therefore, the risk for radiation exposure
is low.
If you
are pregnant or suspect that you may be pregnant,
you should notify your physician. Radiation exposure
during pregnancy may lead to birth defects.
If contrast
dye is used, there is a risk for allergic reaction
to the dye. Patients who are allergic to or sensitive
to medications, contrast dye, iodine, or shellfish
should notify their physician.
Patients
with kidney failure or other kidney problems should
notify their physician. In some cases, the contrast
dye can cause kidney failure, especially if the
person is taking Glucophage (a diabetic medication).
There
may be other risks depending upon your specific
medical condition. Be sure to discuss any concerns
with your physician prior to the procedure.
There
may be other risks depending upon your specific
medical condition. Be sure to discuss any concerns
with your physician prior to the procedure.
Certain
factors or conditions may interfere with the accuracy
of a CT scan of the chest. These factors include,
but are not limited to, the following:
- metallic objects within
the chest, such as surgical clips or a pacemaker
- body piercings on the
chest
- barium in the esophagus
from a recent barium study
- Your physician will
explain the chest CT procedure to you and offer
you the opportunity to ask any questions that
you might have.
- If your procedure involves
the use of contrast dye, you may be asked to
sign a consent form that gives permission to
do the procedure. Read the form carefully and
ask questions if something is not clear.
- Notify the technologist
if you have ever had a reaction to any contrast
dye, or if you are allergic to iodine or seafood.
- Generally, there is
no fasting requirement prior to a CT scan, unless
a contrast dye is to be used. Your physician
will give you special instructions ahead of
time if contrast is to be used and if you will
need to withhold food and drink.
- Notify the technologist
if you are pregnant or suspect you may be pregnant.
- Notify the technologist
if you have any body piercing on your chest
and/or abdomen.
- Dress in clothes that
permit access to the area or that are easily
removed.
- Based upon your medical
condition, your physician may request other
specific preparation.
CT Scanner
A chest
CT may be performed on an outpatient basis or
as part of your stay in a hospital. Procedures
may vary depending on your condition and your
physician's practices.
Generally,
the chest CT follows this process:
- You will be asked to
remove any clothing, jewelry, or other objects
that may interfere with the procedure.
- If you are asked to
remove clothing, you will be given a gown to
wear.
- If you are to have
a procedure done with contrast, an intravenous
(IV) line will be started in the hand or arm
for injection of the contrast dye. For oral
contrast, you will be given a liquid contrast
preparation to swallow.
- You will lie on your
back with your arms above your head on a scan
table that slides into a large, circular opening
of the scanning machine. Pillows and straps
may be used to prevent movement during the procedure.
- The technologist will
be in another room where the scanner controls
are located. However, you will be in constant
sight of the technologist through a window.
Speakers inside the scanner will enable the
technologist to communicate with and hear you.
You will have a call button so that you can
let the technologist know if you have any problems
during the procedure. The technologist will
be watching you at all times and will be in
constant communication.
- As the scanner begins
to rotate around you, low-dosage x-rays will
pass through the body for short amounts of time.
You will hear clicking sounds, which are normal.
- The x-rays absorbed
by the body's tissues will be detected by the
scanner and transmitted to the computer. The
computer will transform the information into
an image to be interpreted by the radiologist.
- It will be important
that you remain very still during the procedure.
- If contrast dye is
used for your procedure, you will be removed
from the scanner after the first set of scans
has been completed. A second set of scans will
be taken after the contrast dye has been administered.
- If contrast dye is
used for your procedure, you may feel some effects
when the dye is injected into the IV line. These
effects include a flushing sensation, a salty
or metallic taste in the mouth, a brief headache,
or nausea and/or vomiting. These effects usually
last for a few moments.
- You should notify the
technologist if you feel any breathing difficulties,
sweating, numbness, or heart palpitations.
- When the procedure
has been completed, you will be removed from
the scanner.
- If an IV line was inserted
for contrast administration, the line will be
removed.
- You may be asked to
wait for a short period of time while the radiologist
examines the scans to make sure they are clear.
While
the CT procedure itself causes no pain, having
to lie still for the length of the procedure might
cause some discomfort or pain, particularly in
the case of a recent injury or invasive procedure
such as surgery. The technologist will use all
possible comfort measures and complete the procedure
as quickly as possible to minimize any discomfort
or pain.
If contrast
dye was used during your procedure, you may be
monitored for a period of time for any side effects
or reactions to the contrast dye, such as itching,
swelling, rash, or difficulty breathing.
If you
notice any pain, redness, and/or swelling at the
IV site after you return home following your procedure,
you should notify your physician as this could
indicate an infection or other type of reaction.
If you
are given contrast by mouth, you may experience
diarrhea after the procedure.
Otherwise,
there is no special type of care required after
a CT scan of the chest. You may resume your usual
diet and activities unless your physician advises
you differently.
Your
physician may give you additional or alternate
instructions after the procedure, depending on
your particular situation.
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