CAT Scan (cont.)
Melissa Conrad Stöppler, MD
Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.
Charles Patrick Davis, MD, PhD
Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.
In this Article
- CT scan facts
- What is a CT scan?
- Why are CT scans performed?
- Are there risks in obtaining a CT scan?
- How does a patient prepare for CT scanning, and how is it performed?
- Find a local Doctor in your town
What is a CT scan?
Computerized (or computed) tomography, and often formerly referred to as computerized axial tomography (CAT) 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. Computerized tomography is more commonly known by its abbreviated names, CT scan or CAT scan. 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 or scanner 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. Contrast material is also often administered intravenously or through other routes prior to obtaining a CT scan (see below). 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 caused by 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.
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