Computerized Axial Tomography
(CAT Scan/CT Scan)
What is a CT scan?
A computerized axial tomography scan
is more commonly known by its abbreviated name, CT scan or CAT scan. It
is an x-ray procedure which combines many
x-ray images with the aid of a computer to generate cross-sectional views and,
if needed, three-dimensional images of the internal organs and structures of the
body. A CT scan is used to define normal and abnormal structures in the body
and/or assist in procedures by helping to accurately guide the placement of
instruments or treatments. A large donut-shaped x-ray machine takes x-ray images
at many different angles around the body. These images are processed by a
computer to produce cross-sectional pictures of the body. In each of these
pictures the body is seen as an x-ray "slice" of the body, which is recorded on
a film. This recorded image is called a tomogram. "Computerized Axial
Tomography" refers to the recorded tomogram "sections" at different levels of the body.
Imagine the body as a loaf of bread and you are looking at one end of the loaf. As you
remove each slice of bread, you can see the entire surface of that slice from
the crust to the center. The body is seen on CT scan slices in a similar
fashion from the skin to the central part of the body
being examined. When these levels are further "added"
together, a three-dimensional picture of an organ or abnormal
body structure can be obtained.
Why are CT scans performed?
CT scans are performed to analyze the internal structures of various parts of the body.
This includes the head, where traumatic injuries, (such as blood clots or skull
fractures), tumors, and infections can be identified. In the spine, the bony
structure of the vertebrae can be accurately defined, as can the anatomy of the intervertebral discs and
spinal cord. In fact, CT scan methods can be used to accurately measure the density of bone in evaluating osteoporosis.
Occasionally, contrast material (an x-ray dye) is placed
into the spinal fluid to further enhance the scan and the various structural
relationships of the spine, the spinal cord, and its nerves. CT scans are also
used in the chest to identify tumors, cysts, or infections that may be suspected
on a chest x-ray. CT scans of the abdomen are extremely helpful in defining
body organ anatomy, including visualizing the liver, gallbladder, pancreas,
spleen, aorta, kidneys, uterus, and ovaries. CT scans in this area are used to
verify the presence or absence of tumors, infection, abnormal anatomy, or
changes of the body from trauma.
The technique is painless and can
provide extremely accurate images of body structures in addition
to guiding the radiologist in
performing certain procedures, such as biopsies of suspected cancers, removal of
internal body fluids for various tests, and the draining of abscesses which are
deep in the body. Many of these procedures are minimally invasive and have
markedly decreased the need to perform surgery to accomplish
the same goal.
Are there risks in obtaining a CT scan?
A CT scan is a very low-risk procedure. The
most common problem is an adverse reaction to intravenous
contrast material. Intravenous contrast is usually an iodine-based liquid
given in the vein, which makes many organs and structures, such as the kidneys
and blood vessels much more visible on the CT scan. There may be resulting
itching, a rash, hives, or a feeling of warmth throughout the body. These are
usually self-limiting reactions and go away rather quickly. If
needed, antihistamines can be given to help relieve the symptoms.
A more serious reaction to intravenous contrast is called an
anaphylactic reaction. When this occurs, the patient may
experience severe hives and/or extreme difficulty in
breathing. This reaction is quite rare, but is potentially life-threatening
if not treated. Medications which may include corticosteroids,
antihistamines, and epinephrine reverse this adverse
reaction.
Toxicity to the kidneys which can result in kidney failure is an extremely rare complication
of the intravenous contrast used in CT scans. Diabetics, dehydrated
individuals, or patients who already have impaired kidney function are most
prone to this reaction. Newer intravenous
contrast agents have been developed, such as Isovue, which have
nearly eliminated this complication.
The amount of radiation a person receives during
a CT scan is minimal. In men and non-pregnant women, it has not been shown to
produce any adverse effects. If a woman is pregnant, there may be a potential
risk to the fetus, especially in the first trimester of the pregnancy. If a
woman is pregnant, she should inform her doctor of her condition and discuss other
potential methods of testing, such as an ultrasound,
which are not harmful to the fetus.
Next: How does a patient prepare for CT scanning, and how is it performed? »
 |
 |
From the Doctors at MedicineNet.com  |
|
|
- Low Blood Pressure - Learn about low blood pressure (hypotension). Low blood pressure is blood pressure below normal and symptoms may include: lightheadedness, dizziness, fainting upon standing (orthostatic hypotension). There are many causes of low blood pressure, and treatment is dependant upon the cause. Source:MedicineNet
- Appendicitis - Appendicitis information including, complications, symptoms, and how inflammation of the appendix is diagnosed and treated Source:MedicineNet
- Abdominal Pain - Learn about abdominal pain (pain in the stomach / abdomen) including causes, symptoms, how abdominal pain is diagnosed, and how abdominal pain is treated. Source:MedicineNet
- Read 108 more CAT Scan related articles ...
|
| |
|
Last Editorial Review: 8/28/2005
Specialty RSS
Ask the Experts