A computerized axial tomography (CAT or CT) scan is an x-ray procedure that 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.
It can be performed to analyze the internal structures of various parts of the body which also includes the head (traumatic injuries such as blood clots or skull fractures, tumors, and infections can be identified), the spine (the bony structure of the vertebrae, anatomy of the intervertebral discs and spinal cord can be accurately defined), the abdomen (it helps to define body organ anatomy, including visualizing the liver, gallbladder, pancreas, spleen, aorta, kidneys, uterus, and ovaries to verify the presence or absence of tumors, infection, abnormal anatomy, or changes of the body from trauma) and the chest (helps to identify tumors, cysts, or infections that may be suspected on a chest x-ray).
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.
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 so if a woman is pregnant, she should inform her doctor of her condition and discuss other potential methods of imaging, such as an ultrasound, which are not harmful to the fetus.
Before the procedure, patients are often asked to avoid food, especially when contrast material is to be used. Occasionally, contrast material (an x-ray dye, usually an iodine-based liquid) 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 but it is often administered intravenously or through other routes prior to obtaining a CT scan.
During the procedure, the patient is placed on a movable table, and the table is slipped into the center of a large donut-shaped x-ray machine which 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 and this recorded image is called a tomogram.
It is important during the CT scan procedure that the patient minimizes any body movement by remaining as still and quiet as is possible. The CT scan technologist tells the patient when to breathe and when to hold breath during scans of the chest and abdomen.
If any problems are experienced during the CT scan, the technologist should be informed immediately. The technologist directly watches the patient through an observation window during the procedure, and there is an intercom system in the room for added patient safety. The actual procedure can take from a half an hour to an hour and a half.
A CT scan is a very low-risk procedure and the most common problem is an adverse reaction to intravenous contrast material. There may be resulting itching, a rash, hives, or a feeling of warmth throughout the body and it usually goes away rather quickly but if needed, antihistamines can be given to help relieve the symptoms.
A more serious allergic reaction to intravenous contrast but quite rare is called an anaphylactic reaction and when this occurs, the patient may experience severe hives and/or extreme difficulty in breathing. Medications which may include corticosteroids, antihistamines and epinephrine can reverse this adverse reaction.