X-Ray
The oldest form of medical imaging using X-Ray radiation to show internal parts of the body.The principle was initially similar to photography in that the image was captured on plates and from these the X-Ray films were developed. Computers have steadily replaced this system. Two views at least are usually taken to allow a 3-D picture to be obtained.
Denser tissues (eg. bone) absorb more X-Rays and are whiter on the films than the corresponding minimally dense tissues (eg. lungs that are predominantly air). Abnormal ’shadowing’ in an area can represent disease and is a result of the different absorption of the X-Rays by different tissues.This is how lung cancers can be identified on Chest X-Rays as the cancer cell growth is denser. Many uses are available for X-Rays but the principle remains the same.i.e to look for changes that should not be there.