The word "tomography" is derived from the Greek tomos (slice) and graphein (to write). The computed assisted tomography was invented by Sir Godfrey Hounsfield in Hayes, United Kingdom at EMI Central Research Laboratories using X-rays. Hounsfield conceived his idea in 1967 and it was publicly announced in 1972. Computed tomography is a powerful radiographic technique for producing 2-D cross-sectional images (and eventually 3-D images) of an object from flat X-ray images. Characteristics of the internal structure of an object such as dimensions, shape, internal defects and density are readily available from CT images.The object to be examined is placed on a turntable stage that is between the radiation source (generally an X-ray tube) and an imaging system (an array of radiation detectors). The turntable and the imaging system are connected to a computer so that X-ray images collected can be correlated to the internal structure of the examined object. The imaging system produces primarly a 2-D shadowgraph image of the object like a film radiograph. Specialized computer softwares make it possible to produce cross-sectional images of the object as if it was being sliced and also reconstruction of its internal structure in 3-D. In the cultural heritage area, computed tomography is used for the non destructive examinatio and study of mummies, metal statues, archeological objects, musical instruments...Medical tomograph (scanners), industrial tomographs ordedicated intruments can be used for such purposes.
CT scanner; computerized axial tomography; examen par tomographie (Fr.); Computer-Tomographie Untersuchung (Deut.)