The cat (Felis catus), also known as the domestic cat or house cat to distinguish it from other felines, is a small predatory carnivorous species of crepuscular mammal that is valued by humans for its companionship and its ability to hunt vermin, snakes and scorpions. It has been associated with humans for at least 9,500 years.5
A skilled predator, the cat is known to hunt over 1,000 species for food. It can be trained to obey simple commands. Individual cats have also been known to learn on their own to manipulate simple mechanisms, such as doorknobs. Cats use a variety of vocalizations and types of body language for communication, including meowing, purring, hissing, growling, squeaking, chirping, clicking, and grunting.6
Cats may be the most popular pet in the world, with over 600 million in homes all over the world.7
They are also bred and shown as registered pedigree pets. This hobby is known as the "cat fancy".
Until recently the cat was commonly believed to have been domesticated in ancient Egypt, where it was a cult animal.8
However a 2007 study found that the lines of descent of all house cats probably run through as few as five self-domesticating African Wildcats (Felis silvestris lybica) circa 8000 BC, in the Near East.4
Pictures of structures within the body created by a computer that takes the data from multiple X-ray images and turns them in pictures on a screen. The CAT (computerized axial tomography) scan can reveal some soft-tissue and other structures that cannot even be seen in conventional X-rays. Using the same dosage of radiation as that of an ordinary X-ray machine, an entire slice of the body can be made visible with about 100 times more clarity with the CAT scan.
The "cuts" (tomograms) for the CAT scan are usually made 5 or 10 mm apart. The CAT machine rotates 180 degrees around the patient's body; hence, the term "axial." The machine sends out a thin X-ray beam at 160 different points. Crystals positioned at the opposite points of the beam pick up and record the absorption rates of the varying thicknesses of tissue and bone. The data are then relayed to a computer that turns the information into a 2-dimensional cross-sectional image.
CAT scanning is painless. Iodine-containing contrast material is sometimes used in CAT scanning. If you are having a CAT scan and are allergic to iodine or other radiocontrast materials, please notify your doctor and the radiology staff.
CAT scanning was invented in 1972 by the British engineer Godfrey N. Hounsfield (later Sir Godfrey) and the South African (later American) physicist Alan Cormack. CAT scanning was already in general use by 1979, the year Hounsfield and Cormack were awarded the Nobel Prize in Medicine or Physiology for its development.
The CAT scan is also known as the CT (computerized tomography) scan.