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CAT Scan Procedure

CAT is an acronym for "computerized axial tomography." CAT has been replaced with a new acronym, CT, that simply stands for "computed tomography." Tomography is the process of making an image of a plane through the body. A CAT scan or a CT scan is a procedure that uses x rays, radiation detectors, and computers to produce images of planes through the body. Rather than using conventional x-ray film to intercept and record information in the x-ray beam that passes through the body, CT scanners use radiation detectors. The x-ray tube and the radiation detectors are positioned on opposite sides of the body. The x-ray tube and detectors rotate around the body. As this is happening, the detectors accumulate information about how much of the x-ray beam passes through the body. This information from the detectors is fed into a computer that performs millions of calculations and determines what must have been in the path of the x-ray beam to absorb x rays the way they were absorbed as they passed through the body. The computer then creates an image that represents a slice (plane) through the body traversed by the x-ray beam. Conventional x-ray procedures give images such as you would see in looking at a hard-boiled egg from the side. CT scans let the radiologists see planes through the egg such as you would see if you put the egg through an egg slicer and then removed each slice and looked down on the top of the egg. As you peel off each slice, you begin to see the yolk getting larger with each slice. Once you pass the middle of the yolk, it begins to get smaller with each slice removed. By creating a series of CT images (slices) down the body, the radiologist can look at each image and get an accurate indication of position, size, and density of objects within the body. Some newer computers can take all of the slices (images of planes through the body) and assemble them into a 3-D image that can be rotated and looked at from various directions. CT scanners are very important diagnostic tools in modern radiology.

Source - (Ken Miller, CHP, Medical Health Physics)