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What a CT scan is and what it does A computed tomography (CT) scan is a relatively
simple, safe, and completely painless examination that radiologists
have performed for many years. The scan produces a series of images
and can detect many conditions that do not show up on conventional
x-rays. Your doctor has ordered this test to help make an accurate
diagnosis of your condition. The results help determine the best course
of treatment for you.
During the scan, a thin beam of x-rays is focused
on a specific part of your body, such as the head, chest, liver, spleen,
pancreas, adrenal glands, kidneys, or spine. The x-ray tube moves rapidly
around this site, enabling multiple images to be made from different
angles to create a cross-sectional picture. The x-ray beam is picked
up by an electronic detector which records the information and feeds
it into a computer.
The computer then analyzes the information and constructs
an image on a TV screen. During some CT scans, a contrast medium (commonly
called "dye") is used to outline blood vessels or highlight
organs of the body (eg, liver, kidneys) so that they can be seen more
easily.
Who performs the test Although your personal physician requests the CT
scan, a radiologist performs the actual examination. A radiologist
is a medical doctor who specializes in the use of imaging
for diagnosis of medical conditions. The radiologist is assisted by a
radiologic
technologist, a person who has extensive training in the
use of x-ray equipment. Together, these highly skilled professionals will
make sure
that your CT scan pictures are of the best quality possible
and that you are as comfortable as possible throughout the procedure.
Where it takes place CT scans can be performed in a hospital radiology
department or, occasionally, in a radiologist ’s office.
How long it takes A CT scan of the body can take from 30 to
90 minutes, while a scan of the head alone can take about
30 minutes. However, you may need to allow extra time for each
procedure in case there are delays or a need to repeat some
scans. Your doctor or the office nurse will advise you how
to plan your schedule for the day of the exam.
What you can do to help make it a success A CT scan is usually completely painless.
The machine does not touch you and you do not feel the x-rays.
Occasionally, some patients who are administered a contrast
medium experience a side effect, usually involving only slight
discomfort. This rarely occurs today because newer, safer
products called nonionic contrast media have been developed, and they
reduce most discomfort.
You can help assure a successful, comfortable
procedure by carefully following the instructions of your physician,
the radiologist, and the radiologic technologist. Be sure to
answer carefully any questions they may ask about your general
health. For example, tell them if you are pregnant, diabetic,
and/or allergic to any foods or drugs. Let them know if you
have had any contrast media in the past and if you had any side
effects. Give them a complete list of any medications you may
be taking now, including nonprescription medications. Also indicate
if you have had or are presently being treated for an infection
in any part of your body.
What to do before your exam This guide provides a step-by-step description
of what to expect before, during, and after your CT scan. But
please remember that it is only a guide. Some steps may
vary depending on your condition, the personal preferences of
your physician, and the standard procedures of the hospital
or office where the test is performed.
As with other important diagnostic procedures,
you may be asked to sign an informed consent to undergo a CT
scan. That is your opportunity to ask any questions following
a description of the risks, benefits, and alternatives of the
procedure. The contents of this guide are for your information
only and are not to be interpreted as taking the place of informed
consent. Do not hesitate to discuss your upcoming CT exam with
your physician or the radiologist.
Following are a few steps that your doctor
may ask you to take before you go to the hospital or radiologist’s
office for your exam. These same general steps may be recommended
if you are a hospitalized patient.
You may need to fast for a few hours If a contrast medium is to be used during
your CT scan, your doctor will probably ask you not to eat anything
for three or four hours or more before the exam. In addition,
you may be asked not to drink anything for one hour before the
exam.
You may need to wear a hospital gown If you are having a body scan, you will probably
be asked to undress and put on a hospital gown for the exam.
You will also be asked to remove any jewelry so that it does
not interfere with the x-ray imaging.
If you are having a CT scan of your head,
you may be asked to wear loose, comfortable clothing for the
exam. And you will need to remove dentures, glasses, hearing
aids, earrings, hairpins, and any other objects that may be
in the path of the x-ray beam.
What happens during your exam
You lie quietly on a table You will be asked to lie on a table that
is connected to the CT scanner. Then the part of your body that
is to be scanned will be positioned in the middle of the large,
doughnut-shaped scanner ring. This ring holds the x-ray tube
and the electronic detector that sends information to the computer.
he technologist may take preliminary scans If a contrast medium is to be used during
your exam, the technologist will probably take some preliminary
scans before the radiologist injects the material.
The radiologist may administer a contrast medium If a contrast medium is used, the radiologist
or technologist will inject it into a vein, probably in your
arm. Some or all of the solution may be injected by a syringe
or by an automatic injector. Some or all of it may run slowly
into your vein from an intravenous (IV) bottle that hangs
on a pole next to the table. A tourniquet may be used to make
the
vein stand out for easier injection. A tourniquet is simply
a band that is wrapped tightly around your arm, similar to,
but smaller than, the cuff that is wrapped around your arm
when you have your blood pressure taken.
The table may move You will remain alone in the room after the
procedure begins, but the radiologist and the radiologic
technologist will watch you closely through an observation window
and you
can talk to them through a two-way intercom.
The table may move a short distance every
few seconds to position you for each new scan, or the table
may move continuously very slowly. You will hear clicking or
buzzing sounds as the mechanism in the scanner moves around
your body, making images from many different angles. It is important
that you lie very still during the procedure so that the scanner
can get the best possible pictures.
The entire procedure may take about an hour
for a body scan and a half-hour for a head scan.
What to do after your exam
Wait for the radiologist to review the scans After the exam is over, the radiologist will
look at all the images to make sure they contain all the needed
information. You will be asked to wait while this is done because
sometimes it is necessary to do repeat scans or take additional
scans.
Dress and return home After the radiologist has a complete set
of scans, you may change back into your clothes and go home.
If you are a hospitalized patient, you may go back to your
room.
Drink plenty of fluids Unless you have other tests scheduled, you
may eat normal meals after the exam and your doctor will
suggest that you drink plenty of fluids. Fluids will help eliminate
the contrast medium from your body.
Meet with your physician The radiologist will study all the scans,
prepare a report, and forward it to your personal physician.
This may take one or two days. Then your physician will discuss
the results with you and tell you what they mean to your
health.
Conclusion We hope this information helps you better
understand what a CT scan is, what it does, and the role
it plays in maintaining your health. If you have any questions
about CT scans that your physician has not answered, please
write them down. Then be sure to discuss these questions
with
your physician before you go to the hospital or radiologist’s
office for your exam. If you are a hospitalized patient,
be sure to ask your questions before you are taken to the radiology
department.
Remember, a CT scan is simple. And it provides
important information about your health.
Glossary allergic: hypersensitive; a condition
in which the body’s immune system reacts with an exaggerated
response to a substance.
computed tomography: an imaging method
in which a cross-sectional picture of the structures in a body
plane are reconstructed using a computer program; the image
is reconstructed from x-ray beams projected through the body.
contrast medium: a dye that is used
to outline or fill up parts of the body that do not ordinarily
show up on an x-ray.
imaging: production of diagnostic
images (pictures)
intravenous: within a vein
Please note that this information is provided for
educational purposes only. It is not intended to substitute for informed
medical advice. The user of this site should not use this information
to diagnose or treat a health problem or disease without consulting with
a qualified health care provider.
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