The term tomography derives from the Greek tomos (cutting) and grapho (to write). Originally the term was

applied to sectional radiography achieved by a synchronous motion of the x-ray source and detector in order

to blur undesired data while creating a sharp image of the selected plane. The term tomography was used to

distinguish between such slices and the more conventional plain film radiograph, which represents a two-

dimensional shadowgraphic superposition of all x-ray absorbing structures within a volumetric body.