CAT Scans (X-ray CT)

A CAT scan (computerized axial tomography scan) makes use of computer-processed combinations of many X-ray images taken from different angles to produce cross-sectional images of specific areas of a scanned object, allowing the user to see inside the object without cutting. Digital geometry processing is used to generate a three-dimensional image of the inside of the object from a large series of two-dimensional radiographic images taken around a single axis of rotation. Medical imaging is the most common application of X-ray CT. Its cross-sectional images are used for diagnostic and therapeutic purposes in various medical disciplines.

CAT scans produce a volume of data that can be manipulated in order to demonstrate various bodily structures based on their ability to block the X-ray beam. Although, historically, the images generated were in the axial or transverse plane, perpendicular to the long axis of the body, modern scanners allow this volume of data to be reformatted in various planes or even as volumetric (3D) representations of structures. Although most common in medicine, CAT scans are also used in other fields, such as nondestructive materials testing. Another example is archaeological uses such as imaging the contents of sarcophagi. Individuals responsible for performing CAT scan exams are called radiographers or radiologic technologists.

Since its introduction in the 1970s, CAT scans have become an important tool in medical imaging to supplement X-rays and medical ultrasonography. It has more recently been used for preventive medicine or screening for disease, for example CAT scan colonography for people with a high risk of colon cancer, or full-motion heart scans for people with high risk of heart disease. A number of institutions offer full-body scans for the general population although this practice goes against the advice and official position of many professional organizations in the field.

The radiation used in CAT scans can damage body cells, including DNA molecules, which can lead to cancer. According to the National Council on Radiation Protection and Measurements, between the 1980s and 2006, the use of CAT scans have increased 600%. The radiation doses received from CAT scans are 100 to 1,000 times higher than conventional X-rays. A study by a New York hospital found that nearly a third of its patients who underwent multiple scans received the equivalent of 5,000 chest X-rays. Some experts note that CT scans are known to be "overused," and "there is distressingly little evidence of better health outcomes associated with the current high rate of scans."