The CAT (Computerized Axial Tomography) scan, also known as the CT (computed tomography) scan, is an x-ray technique that produces a film representing a detailed cross section of tissue structure.
The standard CT scan procedure is painless, noninvasive, and requires no special preparation.
In this test, a computerized axial tomography (CAT or CT) scanner is used to produce a series of cross-sectional x-ray images of a selected part of the body. A computer operates the scanner, and the resulting picture represents a slice of the body. Areas above and below the chosen slice do not appear on the image.
The computer can combine the information in several slices to create other images of the structures inside the body. These images can detect many conditions that cannot be seen in regular x-rays.
It takes the machine only a few seconds to photograph each slice, and 10 to 30 slices are usually taken. The computer then displays the chosen slice on a TV screen. Information from several slices can be combined to create a view across the body from any angle.
The computer calculates tissue absorption, displays a printout of the numeric values, and produces a visualization of the tissues that demonstrates the densities of the various structures. Tumor masses, fractures, bone displacement, and accumulations of fluid can be detected.
Information from the scans is stored in the computer's memory and can be converted into images on a video screen at any time. Photographs of the video screen are taken to record significant findings. The information is then kept in storage on a disk or tape so that it can be examined again if necessary.
It is no overstatement to say that CT scanning has revolutionized the practice of making images of the human body. The CT scanner is the greatest advance in diagnostic imaging since the discovery of x-rays. It produces pictures with 10 to 20 times the detail of regular x-rays, and it can be used to make images of parts of the body that were previously difficult or impossible to obtain.
Use In Diagnosis
CT scans are used throughout the body to diagnose a wide variety of conditions, including the following:
- locate suspected tumors, including Hodgkin's disease, in the space between the two lungs (mediastinum)
- decide whether small lumps in the lung are cancer
- distinguish bulges (aneurysms) of the aorta (a large artery which passes down the back of the chest cavity), from tumors of the chest
- investigate the spread of tumors into the chest from elsewhere in the body
Kidney: confirm the presence of stones, obstructions, tumors, congenital abnormalities, infections, and other diseases of the kidneys
Liver: diagnose tumors, abscesses, and bleeding
Biliary Tract: evaluate reasons for jaundice (yellowing of the skin)
Pancreas: determine if there is a tumor or inflammation of the pancreas
Adrenal glands: look for tumors
Spleen: evaluate suspected injury and other abnormalities
Spine: investigate suspected tumors, injuries, deformities, and other problems of the backbone, discs, and spinal canal