Computerised Axial Tomography

CAT Scans use X-Rays to produce three dimensional images of people’s tissues and bones.

The Scanner-Scanners have large tables that patients lie on, the table moves slowly through a ring that houses the X-Ray tubes that produce the medical X-Rays and the detectors that receive them after they have gone through the patient. Most scanners have both rotating X-Ray tubes and detectors, but some may be surrounded in detectors that don’t rotate. When the X-Rays are detected they are converted into signals and sent to a sophisticated computer which can turn them into a 360 image.

-The scanner does a revolution whilst the table is moving.
-Around every cm the scanner will complete a revolution.
-Each slice scanned is only ~5mm thick so many slices are needed to create an image of a person.
-Scans can take upto 30 minutes if a lot of slices are needed.
The Image-As the X-Rays pass through the patient they are attenuated (Absorbed) by different amounts, the thicker and denser the tissue the X-Rays pass through the greater the X-Rays will be attenuated. The intensity of the X-Rays on arrival at the detectors can determine the amount of tissue the X-Rays have passed through and by using multiple angles the thickness and the densities of the tissues can be calculated by a computer almost like a three dimensional sudoku.
Advantages and Disadvantages-
Non-Invasive, 3D Image, Distinguish between tissues.
Expensive, Ionising Radiation, Can’t be used regularly.