X-ray radiography and CAT scanning are techniques commonly applied in medicine to visualize bone and soft tissue injuries prior to treatment. Because of their non-destructive character, both techniques have also been used to examine the internal structure of archaeological and art objects.
Radiography uses high energy electromagnetic radiation (X-rays, in this case). X-rays penetrate the object and are registered on a photographic film placed behind the object. Variations in composition and thickness are revealed as a result of their differential absorption of X-rays. These variations appear as contrasts (dark and light areas) on the X-ray film.
Computerized Axial Tomography, or CAT scanning, performs cross-sectional imaging (axial slices) of an object. This technique supplements the top-down or side-to-side views provided by direct radiography, and makes possible certain types of three-dimensional reconstruction.
At the University of Illinois, we have been able to image objects ranging from ceramics to mummies, at the College of Veterinary Medicine 's Large Animal Clinic facility. The X-ray unit is rated at 1200 mA and 150 kVp, and the factors used to radiograph museum objects are similar to those used to radiograph the elbow of a person. The CAT scanner was used to image human patients at a local hospital until the early 1990's when it was moved to the Veterinary Teaching Hospital.
