In this technique, a specific plane of an object rotating on a turntable is illuminated by a narrow X-ray beam. After passing through the specimen, the X-rays are recorded by an array of detectors. In more sophisticated facilities, this sequence of slices may then be mathematically assembled into a three-dimensional density map which can be digitally manipulated. Artificial cross-sections, for example, may be generated in any plane, and sequential sections can be linked by means of animation software to simulate the passage of the specimen through a fixed plane. By this means, CT scanning, in a non-destructive manner, provides tomographic information superior to that obtained by physical serial sectioning.
Resolution is a function of the thickness of the slice illuminated by the X-ray beam.
Medical CT scanning facilities generally obtain slice widths of 700 microns or 1400 microns. Although morphologists have used these with some success in studying large specimens, their images of smaller objects are generally poorly resolved. Additionally, such facilities usually store digital information in proprietary, non-exportable formats. Consequently, data analysis must be performed either from hardcopy or at the scanning facility. Despite these limitations, paleontologists, comparative anatomists as well as geologists have obtained useful data from such facilities.